Orthopedic Recon Hip & Knee Board Review | Dr Hutaif Hi -...

Dislocation after total hip arthroplasty is a multifactorial problem. Numerous risk factors may act independently or cumulatively to increase the risk of this complication. Previous hip surgery of any kind is associated with a twofold increased risk for dislocation. Other risk factors include female gender, impaired mental status, inflammatory arthritis, and older age. Numerous studies have shown a lower dislocation rate with a direct lateral approach, although surgical techniques such as capsular repair have significantly lowered the incidence of dislocation after using the posterior approach. Metal-on-metal bearings have been associated with other complications such as adverse tissue reactions but are often used with larger-diameter bearings, which pose a lower risk of dislocation.
**Question 2** A patient has pain 2 years after undergoing a metal-on-metal (MOM) left total hip arthroplasty (THA). Which test(s) best correlate with a prognosis if this patient is having a reaction to metal debris?
1. Erythrocyte sedimentation rate, C-reactive protein, and white blood cell count
2. Serum cobalt and chromium ion levels
3. MRI with metal artifact reduction sequence (MARS)
4. CT of pelvis
CORRECT ANSWER: C DISCUSSION:
Painful MOM THA and taper corrosion can cause substantial damage to a patient's hip if left untreated. In this case, the workup for a painful MOM THA starts the same as a workup for a painful metal-on-polyethylene bearing couple. Infection must be ruled out in every case with a set of inflammatory markers. If these markers are remotely elevated, this is an indication for joint aspiration. In patients with metal debris, the pathology report often indicates too many cells to count or cellular debris. Metal ion levels do not seem to correlate with prognosis. There are well-functioning patients with high ion levels and poor-functioning patients with low ion levels. Advanced imaging with MARS MRI to evaluate for peritrochanteric fluid collection, a soft-tissue mass, or synovial/capsular hypertrophy will reveal signs of a metal reaction that indicate the need for a revision discussion. A CT scan can show more advanced bony destruction as an indicator of poor prognosis. These films can be used to determine the need for a structural graft or augments for reconstruction of bone loss attributable to metal debris.
**Question 3** Figures below demonstrate the radiographs obtained from a 35-year-old woman with end-stage debilitating osteoarthritis of the right hip. She is contemplating total hip arthroplasty (THA). She has a history of right hip dysplasia and underwent hip osteotomy as an adolescent. Over the years, nonsurgical treatment, including weight loss, activity modifications, and intra-articular injections, has failed. Her infection work-up reveals laboratory findings within defined limits. A further work-up reveals elevations in serum cobalt and chromium levels and fluid collections surrounding the hip on MRI with MARS. Revision THA is recommended. The most common complication following revision of a failed metal-on-metal hip arthroplasty is

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1. infection.
2. instability.
3. loosening.
4. periprosthetic fracture.
CORRECT ANSWER: B DISCUSSION:
THA has proven durable and reliable for pain relief and improving function for patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. A metal-on-metal articulation is associated with excellent wear rates in vitro. With its capacity to offer a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis with potential transfer of metal ions across the placental barrier make metal-on-metal bearings less desirable and relatively contraindicated for younger women of childbearing age. The workup of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including sedimentation rate, CRP, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging including MARS MRI should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so, when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cellcounts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following revision of failed metal-on-metal hip replacements.
**Question 4** Figure 1 shows the radiograph and Figure 2 shows the MRI scan obtained from a 37-year-old woman with a 2-month history of left hip pain. Which combination of a single symptom and examination finding is most likely in this scenario?

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D. Buttock pain; pain with hip extension, adduction, and external rotation while prone
1. Pain during sitting; flexion abduction and external rotation of the hip
2. Groin pain; pain with internal rotation and adduction while supine with the hip and knee flexed 90°
3. Clicking; abductor lurch
CORRECT ANSWER: B DISCUSSION:
MRI reveals an anterior labral tear, and the radiograph shows minimal arthritis with possible dysplasia. The most common location of pain in patients with a labral tear is the groin, and the most common physical finding is a positive impingement test result. Pain during sitting, clicking, and buttock pain are frequently described by patients with a labral tear, but these symptoms are less common than groin pain. A positive posterior impingement test finding is more common in patients with a posterior labral tear. Although age over 40 years and a body mass index higher than 30 can adversely affect clinical outcomes after joint preservation procedures such as PAO, hip arthroscopy, and femoral acetabular impingement surgery, the presence of hip arthritis on presurgical radiographs is the most commonly mentioned cause of failed hip joint preservation surgery. Tönnis grade is a radiographic measure of hip arthritis. A higher Outerbridge score is associated with more frequent poor outcomes after hip arthroscopy; however, the Outerbridge cartilage score is determined by direct visualization at the time of surgery. The Outerbridge score cannot be determined presurgically.
**Question 5** Figures 1 and 2 demonstrate the radiographs obtained from a 35-year-old woman with end-stage debilitating osteoarthritis of the right hip. She is contemplating total hip arthroplasty (THA). She has a history of right hip dysplasia and underwent hip osteotomy as an adolescent. Over the years, nonsurgical treatment, including weight loss, activity modifications, and intra-articular injections, has failed. Her infection work-up reveals laboratory findings within defined limits.The patient undergoes successful primary THA with a metal-on-metal bearing. At 1-year follow-up, she reports no pain and is highly satisfied with the procedure. However, 3 years after the index procedure, she reports atraumatic right hip pain that worsens with activities. Radiographs reveal the implants in good position with no sign of loosening or lysis. An initial laboratory evaluation reveals a normal sedimentation rate and C-reactive protein (CRP) level. The most appropriate next diagnostic step is

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1. MRI with metal artifact reduction sequence (MARS) only.
2. serum cobalt only.
3. serum cobalt and chromium levels.
4. serum cobalt and chromium levels and MRI with MARS.
CORRECT ANSWER: D DISCUSSION:
THA has proven to be durable and reliable for pain relief and improvement of function in patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. A
metal-on-metal articulation is associated with excellent wear rates in vitro. Because it offers a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions—including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis after the possible transfer of metal ions across the placental barrier—make metal-on-metal bearings less desirable and relatively contraindicated for younger women of child-bearing age.The work-up of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including the erythrocyte sedimentation rate, C-reactive protein (CRP) level, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging, including MRI with MARS, should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cell counts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following a revision of failed metal-on-metal hip replacements.
**Question 6** A 59-year-old woman with a history of osteoporosis is involved in a high-speed motor vehicle accident, resulting in left hip pain and deformity. The initial radiograph from the trauma bay is shown in Figure 1. Postreduction CT is shown in Figures 2 through 4. What is the most appropriate definitive surgical treatment?

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1. Open reduction and internal fixation (ORIF) of the acetabular fracture with concomitant acute total hip arthroplasty
2. ORIF of the acetabular fracture and ORIF of the femoral head fracture fragments
3. ORIF of the acetabular fracture and hemiarthroplasty
4. Skeletal traction with delayed total hip arthroplasty after the acetabular fracture has healed
CORRECT ANSWER: A
DISCUSSION:
The radiograph shows a posterior wall acetabular fracture-dislocation. Post reduction CT indicates a large comminuted posterior wall fracture with marginal impaction of the articular surface. A comminuted femoral head fracture also is seen extending to the superior weight-bearing surface. Given the marginal
impaction of the acetabulum and the considerable comminution of the femoral head (which is likely unreconstructible), this injury would have a high risk of causing posttraumatic arthritis if treated with ORIF of the fractures alone. Considering this fact and the patient’s age, ORIF of the posterior wall and acute total hip arthroplasty would likely have the best functional result and the lowest risk of reoperation. Hemiarthroplasty is inappropriate for this injury considering the acetabular fracture. Skeletal traction currently plays a limited role in the definitive treatment of acetabular fractures.
**Question 7** Figures below show the radiographs, MRI, and MR arthrogram obtained from a 25-year-old collegiate soccer player who has new-onset left groin pain. He played competitive soccer from a young age and has competed or practiced 5 to 6 times per week since the age of 10. He denies any specific hip injury that necessitated treatment, but his trainer contends that he had a groin pull. He reports groin pain with passive flexion and internal rotation of the left hip, and his hip has less internal rotation than his asymptomatic right hip. He is otherwise healthy. What is the primary cause of a cam deformity?

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1. A genetic problem
2. Repetitive activities involving an open proximal femoral physis
3. Early closure of the proximal femoral physis
4. Hip dysplasia
CORRECT ANSWER: B DISCUSSION:
Multiple studies have confirmed that cam or pincer anatomy is commonly present in asymptomatic hips. According to a large systematic review, cam deformities are present in approximately one-third of asymptomatic hips in young adults, and the proportion is higher than 50% in the subgroup of athletes. Ganz and associates proposed that femoral acetabular impingement is the root cause of osteoarthritis in most nontraumatic, nondysplastic hips, and functional improvement with surgical correction of the deformity has been demonstrated. Despite the link between cam deformity and hip osteoarthritis, a corresponding link between the correction of the deformity and prevention of osteoarthritis has never been proven. The results of cam deformity correction, typically including repair of the degenerative labral tear, are much poorer when substantial joint space loss is present. A typical joint space cutoff of 2 mm or less is used to recommend against hip preservation surgery.
**Question 8** Figures below show the radiographs, and the CT obtained from a 58-year-old woman who underwent cementless left total hip arthroplasty. Nine months after surgery, she continued to have groin pain when actively flexing her hip. She has trouble walking up stairs and getting out of her car. A course of appropriate nonsurgical treatment failed. What is the next step in definitive treatment?

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1. Acetabular component revision
2. Femoral component revision
3. Acetabular liner exchange
4. Trochanteric bursectomy
Submit Answer
**Question 9** What factor is associated with a high risk of developing pseudotumors after metal-on-metal hip resurfacing?
1. Large-diameter components
2. Age 40 or older for men
3. Age 40 or younger for women
4. Diagnosis of primary osteoarthritis
CORRECT ANSWER: C DISCUSSION:
The recent experience of a large clinical cohort revealed the most likely risk factors as being female gender, age younger than 40, small components, and a diagnosis of hip dysplasia causing osteoarthritis. Failure was least likely among men and after procedures involving larger components. These data have prompted some authors to caution against using metal-on-metal hip resurfacing in women and to primarily target candidates who are men younger than age 50. Small components may be more prone to failure because of malpositioning and edge loading, which have been noted to be more common in dysplasia cases.
**Question 10** Figures below show the radiographs, MRI, and MR arthrogram obtained from a 25-year-old collegiate soccer player who has new-onset left groin pain. He played competitive soccer from a young age and has competed or practiced 5 to 6 times per week since the age of 10. He denies any specific hip injury that necessitated treatment, but his trainer contends that he had a groin pull. He reports groin pain with passive flexion and internal rotation of the left hip, and his hip has less internal rotation than his asymptomatic right hip. He is otherwise healthy.When counseling patients who have a cam deformity, the orthopaedic surgeon should note that

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1. osteoarthritis of the hip is likely to occur later in life.
2. correction prevents later development of osteoarthritis.
3. most acetabular tears are symptomatic, and surgical treatment will be necessary.
4. this is an inherited deformity.
CORRECT ANSWER: A DISCUSSION:
Multiple studies have confirmed that cam or pincer anatomy is commonly present in asymptomatic hips. According to a large systematic review, cam deformities are present in approximately one-third of asymptomatic hips in young adults, and the proportion is higher than 50% in the subgroup of athletes. Ganz and associates proposed that femoral acetabular impingement is the root cause of osteoarthritis in most nontraumatic, nondysplastic hips, and functional improvement with surgical correction of the deformity has been demonstrated. Despite the link between cam deformity and hip osteoarthritis, a corresponding link between the correction of the deformity and prevention of osteoarthritis has never been proven. The results of cam deformity correction, typically including repair of the degenerative labral tear, are much poorer when substantial joint space loss is present. A typical joint space cutoff of 2 mm or less is used to recommend against hip preservation surgery.
**Question 11** Figures below demonstrate the radiographs obtained from a 63-year-old man who had right total hip arthroplasty (THA) 4 months ago. Progressive stiffness began 2 months after surgery, and he now reports pain only after prolonged physical activity. His examination reveals a normal gait and painless range of motion with flexion of 70°, extension of 0°, internal rotation of 20°, external rotation of 20°, abduction of 10°, and adduction of 10°. His erythrocyte sedimentation rate and C-reactive protein level are within defined limits. Physical therapy has produced no benefit. What is the most appropriate next step?

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1. 25 mg of indomethacin 3 times daily for 6 weeks
2. 1 dose of irradiation at 800 Gy
3. Surgical excision of heterotopic ossification (HO)
4. Reevaluation in 6 months
CORRECT ANSWER: D DISCUSSION:
This patient presents with HO 4 months after undergoing THA. Symptomatic HO may complicate nearly 7% of primary THA cases. Improvement in pain is expected within 6 months, and most patients will not need surgical treatment. Surgical excision may be warranted for symptomatic patients after full maturation of the HO, usually 6 to 18 months after the surgery. Patients can be followed with repeated serum alkaline phosphatase levels, which are elevated initially and should return to normal upon maturation of the HO. Alternatively, a bone scan can show decreased activity after the HO has matured. Twenty-five milligrams of indomethacin 3 times daily for 6 weeks or 1 dose of irradiation at 700 to 800 Gy is effective in the prevention of HO but not for the treatment of established HO.
**Question 12** A 55-year-old man is about to undergo right total hip arthroplasty. A preoperative AP pelvis radiograph is shown in Figure below. The final acetabular component and polyethylene liner are implanted. With the broach in place, the surgeon trials a standard offset neck and neutral length femoral head. The leg lengths are approximately equal, but the hip is unstable. What is the best next step?

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1. Choosing a longer femoral head and accepting a resulting leg-length discrepancy
2. Trialing a lateralized femoral neck component
3. Removing the acetabular liner and implanting an offset liner instead
4. Performing a trochanteric osteotomy with advancement
CORRECT ANSWER: B
DISCUSSION:
The radiograph shows that this patient has a high offset varus femoral morphology of both hips. Preoperative templating would identify this, and the surgeon should choose an implant system that has extended offset options to help match the native anatomy and biomechanics and minimize the risk of instability. Trialing a high offset neck, rather than a standard offset neck, is the next most appropriate step. Depending on the design of the implant system, this step can be accomplished by direct medialization of the femoral head, which would not affect leg length, or by lowering the neck angle, which would affect the leg length and would require a longer femoral head, because the leg lengths had previously been equal. Placement of a longer femoral head would likely improve hip stability but would also make the leg length uneven, which is a common cause of dissatisfaction after total hip arthroplasty. An offset acetabular liner also increases the leg length and does not correct the issue, which is on the femoral side. Trochanteric
advancement is sometimes used as a treatment for instability but would be inappropriate as the next step in this setting.
**Question 13** During total hip arthroplasty, what characteristic of irradiated (10 Mrad) and subsequently melted highly cross-linked polyethylene should provide a more wear-resistant construct than traditional gamma-irradiated (2.5-4 Mrad)-in-air polyethylene mated with the same head?
1. Resistance to adhesive wear
2. Resistance to abrasive wear
3. Resistance to fatigue wear
4. Resistance to creep
CORRECT ANSWER: B
DISCUSSION:
Highly cross-linked polyethylene makes material resistant to adhesive wear. Abrasive wear from third bodies does not decrease wear. The fatigue strength of such material is inferior to that of traditional polyethylene, and its resistance to creep is the same, if not lower, than that of traditional polyethylene.
**Question 14** When compared with patients having a body mass index (BMI) lower than 35, patients with a BMI above 40 who undergo primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) are
likely to have
1. smaller incisions.
2. more wound complications.
3. fewer 30-day and 90-day readmissions.
4. lower rates of patient satisfaction.
CORRECT ANSWER: B
DISCUSSION:
The obesity epidemic is increasing, and the number of patients with a BMI higher than 35 undergoing THA and TKA also is growing. Controversy exists over the optimal BMI cutoff and the ability to perform joint replacements safely in patients who are morbidly obese. Several clinical series and national database analyses have shown that morbidly obese patients undergoing THA or TKA are at increased risk for wound complications as well as 30-day and 90-day readmissions. These patients’ incisions are typically larger because of the size of the soft-tissue envelope. Although the clinical scores following successful THA or TKA often are lower than the scores of controls, the overall changes in clinical function and satisfaction are equivalent in nonobese and obese patients.
**Question 15** An otherwise healthy 76-year-old woman has pain 2 years after total hip arthroplasty. The clinical photograph in Figures below demonstrates her skin envelope, and associated radiograph. Her C-reactive protein level is normal, and her erythrocyte sedimentation rate is mildly elevated. The white blood cell count is normal. Hip aspiration attempted under fluoroscopy generates no fluid. What is the best definitive treatment?

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1. Repeat left hip aspiration
2. Initiation of a wound care consult and oral antibiotics
3. Irrigation and debridement with closure of the dehisced wound, performance of a liner exchange, and administration of intravenous antibiotics
4. Debridement of the wound, explant of the total hip, placement of a spacer, and administration of intravenous antibiotics
CORRECT ANSWER: D
DISCUSSION:
This patient clearly has a chronically infected total hip arthroplasty, indicated by the open, draining sinus, as well as trochanteric bone resorption on radiographs, and two years of pain. Recently, specific guidelines have been published to better help the clinician define infection. Repeating the hip aspiration is unnecessary, because infection is already evident. Initiating a wound care consult would not address the underlying infection. The determination whether to retain the components or perform a two-stage exchange is based more on the acuity of infection. In this particular case, the patient is chronically infected. Irrigation and debridement with a liner exchange and retention of the components are reserved for the acute setting.
**Question 16** Figures below show the radiographs obtained from a 90-year-old woman who is seen in the emergency department after a fall from a height. She has right hip and thigh pain and is unable to bear weight. Based on this patient's history and imaging, what is the best next step?

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1. Hip revision and implantation of a proximal femoral replacement
2. Hip revision and implantation of a tapered fluted stem
3. Open reduction and internal fixation with a locked plate and allograft struts
4. Erythrocyte sedimentation rate and C-reactive protein laboratory studies
CORRECT ANSWER: D
DISCUSSION:
Periprosthetic fracture is the third most common reason (after loosening and infection) for revision surgery after total hip arthroplasty (THA). Late periprosthetic fracture risk is 0.4% to 1.1% after primary
THA and 2.1% to 4% after revision THA. Risk factors for periprosthetic fracture include age over 70 years, decreasing bone mass, and loosening of implants and osteolysis. The risk of concomitant infection in the presence of a periprosthetic fracture is 11%, according to Chevillotte and associates. Obtaining presurgical aspiration or intrasurgical tissue for culture is recommended if concomitant infection is suspected.
**Question 17** Figure below shows the radiograph obtained from a 73-year-old woman who returns status post total hip arthroplasty 14 years earlier. She denies pain and has no discomfort on examination. She then undergoes revision total hip arthroplasty with head and liner exchange and bone grafting. After a physical therapy session two days after surgical intervention, she develops inability to dorsiflex the foot while she is sitting in a chair. The initial treatment should consist of

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1. lying completely supine in bed.
2. remaining seated and placing the postsurgical leg on a stool.
3. transferring back to bed with the head of the bed no lower than 60°.
4. transferring back to bed with the head of the bed level and the surgical knee flexed.
CORRECT ANSWER: D
DISCUSSION:
Gamma irradiation produces free radicals. Although these free radicals can form cross-links with other polyethylene chains, the free radicals can also form a bond with oxygen, resulting in early oxidation. Gamma irradiation in air produces the highest risk for oxidized polyethylene, resulting in the highest risk for wear, delamination, and subsequent osteolysis. This patient demonstrates severe periarticular osteolysis. When she is asymptomatic, this suggests the acetabular and femoral components remain well fixed to the bone. Consequently, she can be treated by removing the wear generator (polyethylene exchange), along with bone grafting of the osteolytic defect. Considering the extensive amount of osteolysis indefinite observation would not be appropriate. A foot drop develops 2 days after surgery. As a result, it can be assumed that the nerve was not injured directly during the surgical procedure. Although MRI or CT may be indicated to identify an evolving hematoma, the immediate concern is to minimize pressure on the sciatic nerve. Tension on the nerve can be reduced by flexing the surgical knee and positioning the bed flat.
**Question 18** Figure below depicts the radiograph obtained from a 52-year-old woman who has leg-length inequality and chronic, activity-related buttock discomfort. This problem has been lifelong, but it is getting worse and increasingly causing back pain. What is the best current technique for total hip arthroplasty?

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1. High hip center
2. Anatomic hip center with trochanteric osteotomy and progressive femoral shortening
3. Anatomic hip center with subtrochanteric shortening osteotomy
4. Iliofemoral lengthening followed by an anatomic hip center
CORRECT ANSWER: C
DISCUSSION:
A high hip center is not recommended for Crowe type IV hips because of the lack of acetabular bone and altered hip biomechanics. An anatomic center is a better option but necessitates a technique to address the tight soft-tissue envelope. A trochanteric osteotomy with progressive femoral shortening has been described but can be prone to trochanter nonunion. Iliofemoral lengthening prior to surgery has been described but may not be tolerated by all patients. A shortening subtrochanteric osteotomy avoids trochanter nonunion and allows adjustment of femoral anteversion. Fixation of the osteotomy can include a stem with distal rotational control, plate fixation, a step versus oblique cut, or strut grafts.
**Question 19** Figures 1 through 5 show the radiographs, MRI, and MR arthrogram obtained from a 25-year-old collegiate soccer player who has new-onset left groin pain. He played competitive soccer from a young age and has competed or practiced 5 to 6 times per week since the age of 10. He denies any specific hip injury that necessitated treatment, but his trainer contends that he had a groin pull. He reports groin pain with passive flexion and internal rotation of the left hip, and his hip has less internal rotation than his asymptomatic right hip. He is otherwise healthy. Approximately what percentage of asymptomatic athletes have cam deformities of the hip?

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1. 5%
2. 10%
1. 25%
2. At least 50%
CORRECT ANSWER: D
DISCUSSION:
Multiple studies have confirmed that cam or pincer anatomy is commonly present in asymptomatic hips. According to a large systematic review, cam deformities are present in approximately one-third of asymptomatic hips in young adults, and the proportion is higher than 50% in the subgroup of athletes. Ganz and associates proposed that femoral acetabular impingement is the root cause of osteoarthritis in most nontraumatic, nondysplastic hips, and functional improvement with surgical correction of the deformity has been demonstrated. Despite the link between cam deformity and hip osteoarthritis, a corresponding link between the correction of the deformity and prevention of osteoarthritis has never been proven. The results of cam deformity correction, typically including repair of the degenerative labral tear, are much poorer when substantial joint space loss is present. A typical joint space cutoff of 2 mm or less is used to recommend against hip preservation surgery.
**Question 20** A 59-year-old active woman undergoes elective total hip replacement in which a posterior approach is used. She has minimal pain and is discharged to home 2 days after surgery. Four weeks later, she dislocates her hip while shaving her legs. She undergoes a closed reduction in the emergency department. Postreduction radiographs show a reduced hip with well-fixed components in satisfactory alignment. What is the most appropriate management of this condition from this point forward?
1. Observation and patient education regarding hip dislocation precautions
2. Revision to a larger-diameter femoral head
3. Revision to a constrained acetabular component
4. Application of a hip orthosis for 3 months
CORRECT ANSWER: A
DISCUSSION:
First-time early dislocations are often treated successfully without revision surgery, especially when no component malalignment is present. In this clinical scenario, it appears the patient would benefit from better education about dislocation precautions. Hip orthoses are of questionable benefit unless the patient is cognitively impaired. Revision surgery can be successful but is usually reserved for patients with recurrent dislocations.
**Question 21** A 62-year-old active man returns for routine follow-up 16 years after hip replacement. He has no hip pain. Radiographs reveal a well-circumscribed osteolytic lesion around a single acetabular screw. All hip components are perfectly positioned. Comparison radiographs obtained 6 months later show an increase in the size of the osteolytic lesion. CT depicts a well-described lesion that is 3 cm at its largest diameter and is localized around one screw hole with an eccentric femoral head. What treatment is appropriate, assuming that well-fixed cementless total hip components are in place?
1. Revision of the polyethylene liner, removal of the screw, and debridement of the osteolytic lesion with or without bone grafting
2. Revision of the acetabular component to a newer design without screws
3. Removal of the screw, revision of the polyethylene liner, and stem cell injection into the lytic lesion
4. Removal of the offending screw from the metal socket and placement of a new polyethylene liner in the existing socket
CORRECT ANSWER: A
DISCUSSION:
Given a well-fixed acetabular metal shell and a localized osteolytic lesion, good outcomes can be expected from liner revision in this clinical scenario with retention of the metal socket, assuming no damage to the components or other unexpected findings arise during revision surgery. Here, complete cup revision is not warranted, considering the appropriate implant position. Beaulé and associates reviewed 83 consecutive patients (90 hips) in whom a well-fixed acetabular component was retained in a clinical scenario such as the one described. No hip showed recurrence or expansion of periacetabular osteolytic lesions. If the metal cup is unstable, acetabular component revision may be indicated.
**Question 22** Figure 1 shows the radiograph obtained from a 78-year-old woman who has a recent history of increasing thigh pain 12 years after undergoing total hip arthroplasty. Figure 2 depicts the radiograph obtained after she fell and was unable to ambulate. What is the most appropriate treatment?

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1. Application of a femoral cable plate
2. Application of cerclage-wired double allograft femoral struts
3. Femoral revision with an uncemented long stem
4. Femoral revision with a cemented long-stem prosthesis
CORRECT ANSWER: C
DISCUSSION:
The surgical treatment of periprosthetic fractures of total hip replacement with a loose implant and progressive bone loss is associated with a high complication rate. The recent literature would favor the use of long "Wagner-type" stems, which have a long distal taper that may optimally engage the remaining femoral shaft isthmus. Plating options are problematic, because the intramedullary stem limits the ability to use screws with the plate. Using long distally fixed stems circumvents this problem by enhancing fracture healing and creating a long-term prosthetic solution in these most difficult cases.
**Question 23** Early postoperative infections following primary total hip arthroplasty are most likely caused by which organism?
1. Staphylococcus epidermidis
2. Streptococcus viridans
3. Propionibacterium acnes
4. Staphylococcus aureus
CORRECT ANSWER: D
DISCUSSION:
_S aureus is the most common organism cultured in early (fewer than 4 weeks postoperative) periprosthetic infections. Methicillin-resistant S aureus is becoming a more common pathogen in certain patient populations. B hemolytic Streptococcus and some gram-negative infections can also be found in early postoperative infections. S epidermidis, S viridans, and P acnes are more commonly found in late (more than 4 weeks postoperative) infections._
**Question 24** A healthy, active 72-year-old man trips and falls, landing on his left hip 10 weeks after an uncomplicated left primary uncemented total hip replacement. A radiograph taken 6 weeks after surgery and before the fall is shown in Figure 1. A radiograph taken after the fall is shown in Figure 2. He is unable to bear weight and is brought to the emergency department. Examination reveals a slightly shortened left lower extremity and some mild ecchymosis just distal to the left greater trochanteric region, but his skin is intact, without abrasions or lacerations. What is the most appropriate treatment?

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1. Open reduction and cerclage fixation of the fracture
2. Open reduction and revision of the femoral implant to a long cemented stem
3. Open reduction and revision of the femoral implant to a long fluted and tapered uncemented stem
4. Application of balanced traction followed by surgery after the ecchymosis has resolved
CORRECT ANSWER: D
DISCUSSION:
This patient has a periprosthetic femoral fracture with a loose femoral stem and normal femoral bone stock, representing a Vancouver type B2 fracture. The most appropriate treatment is fixation of the fracture, along with revision of the stem. Considering his age, bone quality, and activity level, a longer uncemented stem is most predictable. Although a cylindrical stem may also be used, the fluted stem option is the only uncemented choice listed and is the most appropriate option. A cemented stem is a poorer choice because it is difficult to keep the cement out of the fracture site, which would pose a risk for nonunion at the fracture. Also, overall poorer results have been associated with long cemented stems in healthy, active people. Surgery does not need to be delayed to allow the ecchymosis to resolve, and simple open reduction and fixation does not address the loose stem.
**Question 25** A 70-year-old man undergoes removal of an infected total hip arthroplasty (THA) and insertion of an articulating antibiotic-loaded spacer to treat a deep periprosthetic hip infection. While in a nursing home receiving intravenous antibiotics 3 weeks after surgery, the patient trips and falls. Examination reveals swelling in the mid and distal thigh, intact skin and neurovascular structures, and severe pain with knee or hip movement. Radiographs of the femur are shown in Figures 1 through 4. What is the most appropriate treatment for the fracture below the implant?

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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/HK-3_Fig-06a-1543610199711.jpg)
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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/HK-3_Fig-06a-1543610199711.jpg)
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1. Balanced traction to address concern for persistent infection with reoperation
2. Open reduction and internal fixation of the fracture with a lateral plate and screws
3. Removal of the articulating spacer and revision to a longer-stem antibiotic-loaded articulating spacer
4. Removal of the articulating spacer and reimplantation using a long-stem fluted uncemented hip replacement
CORRECT ANSWER: B
DISCUSSION:
This patient has a type C periprosthetic femoral fracture. The articulating spacer is not involved in the fracture, which is well distal to the implant. The most appropriate treatment is open reduction and internal fixation of the fracture. Traction is not appropriate for this fracture because the injury can be treated surgically despite the history of previous hip infection. Traction would also be needed for at least 5 weeks and would delay the surgical treatment of the periprosthetic fracture until the time of second-stage revision THA. The fracture is fairly distal, and revision to a longer antibiotic-loaded implant or uncemented stem is not suitable for this fracture pattern, because it extends well past the isthmus. A femoral stem in the distal fragment would provide little stability for the fracture. Removal of the articulating spacer and reimplantation using a long-stem fluted uncemented hip replacement is not appropriate, because it would be premature to reimplant the man's hip while he is still receiving treatment for a deep hip infection.
**Question 26** Figures 1 and 2 demonstrate the radiographs obtained from a 35-year-old woman with end-stage debilitating osteoarthritis of the right hip. She is contemplating total hip arthroplasty (THA). She has a history of right hip dysplasia and underwent hip osteotomy as an adolescent. Over the years, nonsurgical treatment, including weight loss, activity modifications, and intra-articular injections, has failed. Her infection work-up reveals laboratory findings within defined limits. Which bearing surface is contraindicated for this patient?

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1. Ceramic-on-ceramic
2. Ceramic-on-highly cross-linked polyethylene (HXPE)
3. Metal-on-HXPE
4. Metal-on-metal
CORRECT ANSWER: D
DISCUSSION:
THA has proven durable and reliable for pain relief and improving function for patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. A metal-on-metal articulation is associated with excellent wear rates in vitro. With its capacity to offer a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis with potential transfer of metal ions across the placental barrier make metal-on-metal bearings less desirable and relatively contraindicated for younger women of childbearing age. The workup of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including sedimentation rate, CRP, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging including MARS MRI should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so, when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cell counts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following revision of failed metal-on-metal hip replacements.
**Question 27** Figures below show the radiograph and the MRI scan obtained from a 37-year-old woman with a 2-month history of left hip pain. Which presurgical factor is most commonly associated with a poor outcome after a hip joint salvage procedure?

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1. Age older than 40 years
2. Body mass index higher than 30
3. Tönnis grade of 2 or higher
4. Outer bridge grade of III or IV
CORRECT ANSWER: C
DISCUSSION:
MRI reveals an anterior labral tear, and the radiograph shows minimal arthritis with possible dysplasia. The most common location of pain in patients with a labral tear is the groin, and the most common physical finding is a positive impingement test result. Pain during sitting, clicking, and buttock pain are frequently described by patients with a labral tear, but these symptoms are less common than groin pain. A positive posterior impingement test finding is more common in patients with a posterior labral tear. Although age over 40 years and a body mass index higher than 30 can adversely affect clinical outcomes after joint preservation procedures such as PAO, hip arthroscopy, and femoral acetabular impingement surgery, the presence of hip arthritis on presurgical radiographs is the most commonly mentioned cause of failed hip joint preservation surgery. Tönnis grade is a radiographic measure of hip arthritis. A higher Outerbridge score is associated with more frequent poor outcomes after hip arthroscopy; however, the
Outerbridge cartilage score is determined by direct visualization at the time of surgery. The Outerbridge score cannot be determined presurgically.
**Question 28** Figure below shows the radiograph obtained from a 68-year-old man who fell 3 weeks after undergoing a successful left primary total hip arthroplasty. He is experiencing a substantial increase in pain and an inability to bear weight. What is an appropriate treatment plan?

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1. Open reduction and internal fixation (ORIF) of the fracture
2. Removal of the current stem, femur ORIF, and insertion of a longer revision stem
3. Femur ORIF with cables and strut graft, leaving the current stem in situ
4. Femur ORIF combined with reimplantation of the primary component
CORRECT ANSWER: B
DISCUSSION:
The fracture has occurred around the stem, representing a Vancouver type B fracture, and the stem is clearly loose, making it a type B2 fracture. The appropriate treatment is removal of the loose in situ stem; ORIF of the femur using cerclage wires, cables, or a plate; and insertion of a longer revision stem such as a tapered fluted modular titanium or fully porous coated cylindrical stem to bypass the fracture. All of the other options are incorrect, because they represent inappropriate treatment options for a Vancouver type B2 fracture.
**Question 29**
What factor is associated with a higher risk of dislocation after total hip arthroplasty?
1. Male gender
2. Previous hip surgery
3. A direct lateral surgical approach
4. Metal-on-metal bearing surfaces
CORRECT ANSWER: B
DISCUSSION:
Dislocation after total hip arthroplasty is a multifactorial problem. Numerous risk factors may act independently or cumulatively to increase the risk of this complication. Previous hip surgery of any kind is associated with a twofold increased risk for dislocation. Other risk factors include female gender, impaired mental status, inflammatory arthritis, and older age. Numerous studies have shown a lower dislocation rate with a direct lateral approach, although surgical techniques such as capsular repair have
significantly lowered the incidence of dislocation after using the posterior approach. Metal-on-metal bearings have been associated with other complications such as adverse tissue reactions but are often used with larger-diameter bearings, which pose a lower risk of dislocation.
**Question 30** Figures below show the radiographs obtained from a 19-year-old woman with a 3-year history of progressive hip pain in the left groin with activity, which is unresponsive to activity modification and physical therapy. Examination reveals normal range of motion, with pain on anterior impingement testing. What treatment is associated with the best long-term results?

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1. Hip arthroscopy with labral repair
2. Reverse periacetabular osteotomy
3. Varus rotational osteotomy
4. Open surgical dislocation with rim trimming
CORRECT ANSWER: B
DISCUSSION:
This patient has symptomatic femoroacetabular impingement as well as clinical and radiographic signs of acetabular retroversion, including a cross-over sign, ischial spine sign, and posterior wall sign bilaterally. Good midterm to long-term outcomes have been reported with reverse (anteverting) Bernese periacetabular osteotomy (PAO). In patients with less retroversion, open or arthroscopic rim trimming with labral refixation have shown good short-term results, but longer-term results have yet to be fully delineated. Isolated hip arthroscopy and labral repair would not be indicated without addressing the retroversion deformity. Femoral varus rotational osteotomy plays no role in the treatment of this pathology. Open surgical dislocation with rim trimming could be considered in patients with less deformity, but some studies have shown inferior long-term results compared with reverse PAO.
**Question 31** Figure below depicts the radiograph obtained from a 30-year-old woman who began having more right than left hip pain during a recent pregnancy. Physical examination reveals increased range of motion with positive flexion abduction and external rotation and flexion adduction and internal rotation as well as pain with external logroll. Assessment of Figure below reveals

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1. classic dysplasia with volume deficient acetabula.
2. acetabular retroversion with positive crossover signs and ischial spine signs.
3. no substantial dysplasia, with normal acetabular volume and anteversion.
4. inadequate radiographic evidence to assess for hip dysplasia.
CORRECT ANSWER: D
DISCUSSION:
Studies have demonstrated that pelvic inclination can dramatically affect the interpretation of radiographs in the dysplastic hip, with 9° of increased pelvic inclination leading to the presence of crossover signs and posterior wall signs. A distance of 30 mm to 50 mm from the sacrococcygeal junction to the pubis is often used to assess the adequacy of pelvic inclination on radiographs, although Siebenrock and associates determined the mean difference to be 32 mm in men and 47 mm in women. In this patient, the pelvic inclination is dramatically increased, leading to overestimation of acetabular retroversion.
**Question 32** In patients with Crowe types III and IV developmental dysplasia of the hip with high hip centers, acetabular reconstruction often requires lowering the acetabular component into the native acetabulum. In doing so, considerable risk for limb lengthening beyond 4 cm exists, making the hip difficult to reduce and raising the risk for nerve injury. Which technique is used to overcome this problem?
1. Subtrochanteric osteotomy with femoral shortening
2. An offset femoral component
3. A lateralized liner
4. Extended trochanteric osteotomy
CORRECT ANSWER: A
DISCUSSION:
When substantial lengthening of a dysplastic hip will occur because a high dislocation is relocated into a considerably lower acetabulum, a femoral shortening may be necessary to reduce the hip and avoid a stretch injury to the sciatic nerve. No other choice specifically addresses the need for femoral shortening, and high offset stems and lateralized liners may exacerbate the problem if used alone and without femoral shortening.
**Question 33** Figures 1 through 3 show the radiograph and MR arthrograms obtained from a 25-year-old woman who has had right groin pain since joining the military 4 years ago. She has undergone treatment with NSAIDs, physical therapy, and activity modification. Examination reveals positive flexion abduction and external rotation, a positive external log roll, and increased range of motion. What is the most appropriate treatment?

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1. Viscosupplementation of the right hip
2. Hip arthroscopy with labral repair
3. Periacetabular osteotomy
4. Total hip arthroplasty
CORRECT ANSWER: C
DISCUSSION:
This patient has symptomatic hip dysplasia that has been recalcitrant to nonsurgical management. Radiographs reveal an upsloping sourcil (acetabular index of 18) and a lateral center edge angle of 14, with posterior uncovering. The MR arthrogram shows no definitive evidence of a labral tear. Appropriate surgical management would include periacetabular osteotomy. Viscosupplementation in the hip is controversial in the treatment of osteoarthritis and plays no role in the treatment of dysplasia. Hip arthroscopy with labral repair is controversial in mild hip dysplasia, with studies demonstrating between 60% and 77% good and excellent results, inferior to the results for hip arthroscopy in a femoroacetabular impingement cohort. In moderate to severe dysplasia, hip arthroscopy is not recommended. Because the acetabular cartilage is well maintained, total hip arthroplasty would not be recommended in this young and active patient.
**Question 34** Figures 1 and 2 show the radiographs obtained from a 68-year-old morbidly obese man who underwent left total hip replacement 7 years ago and did well, with no symptoms prior to the current presentation. He recently rose from a seated position and felt a pop in the hip, with immediate pain and inability to bear weight. Any pressure on the left foot now produces a painful, grinding sensation with loss of left hip stability. What is the best next step?

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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/540604F1-1543613620740.jpg)
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1. Revision of the acetabular implant to a constrained bearing with modular exchange of the femoral head and neck
2. Revision of the acetabular and femoral implants
3. Retention of the acetabular implant with modular exchange of the femoral head and neck
4. Revision of the femoral component alone with a new ceramic head
CORRECT ANSWER: B
DISCUSSION:
The modular femoral stem has fractured. Changing the liner to a constrained design is not warranted at this time based on the information provided. Revision of the acetabular implant is appropriate because of the potential for damage to the existing cup from metal debris and femoral implant contact and to convert from a metal-on-metal articulation. Nonsurgical management would not provide pain relief or improvement; revision of the total hip arthroplasty is recommended. The implant failed in a short time, and retention of the femoral stem is not recommended because of the concern for failure with only a neck exchange. A dual-mobility bearing may be a good option if the surgeon plans to retain the acetabular component. Extended trochanteric osteotomy is a useful technique for the removal of a well-fixed femoral implant. In this patient, femoral stem removal without
osteotomy would be difficult due to the fracture of the implant’s femoral neck and the inability to gain purchase for extraction.
**Question 35**
A 63-year-old woman had a primary total hip arthroplasty 7 years ago that included a proximally coated
titanium stem, a cobalt alloy femoral head, a titanium hemispherical acetabular component, and a polyethylene liner. She did well for 4 years but has now had two dislocations and reports pain and weakness around the left hip. She denies any fevers, chills, or constitutional symptoms. On examination, the patient walks well without any signs of an antalgic or Trendelenburg gait. Her abductor mechanism demonstrates good strength. Her erythrocyte sedimentation rate and C-reactive protein level are normal. On radiographs, all components appear well fixed and in good alignment. What is the most appropriate treatment at this time?
1. Physical therapy to improve hip stability
2. Use of an abduction brace to limit the patient’s range of motion
3. Conversion to a constrained acetabular liner
4. Cobalt and chromium serum metal ion level testing
CORRECT ANSWER: D
DISCUSSION:
Trunnionosis is a recently recognized complication following total hip arthroplasty and can occur when a cobalt alloy femoral head is used on a titanium alloy or cobalt alloy femoral stem. Patients often present with pain or swelling around the hip but at times can present with instability. Certain femoral stem designs have been associated with increased reports of trunnionosis. In a patient with a cobalt alloy femoral head who presents with instability, swelling, and weakness around the hip, the potential for trunnionosis and
an adverse local tissue reaction should be considered.
**Question 36** Figures below show the radiographs obtained from a 68-year old man with progressively worsening right side hip pain over the last 8 months. He is 6 feet tall, with a BMI of 51 kg/m2 and reports that his index total hip arthroplasty was performed 8 years ago. The preoperative work-up includes negative infectious laboratory results. What is the most appropriate surgical plan for revision of the femoral component in this patient?

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1. Superior approach with trochanteric slide
2. Direct anterior approach with a chevron modification of the standard greater trochanteric osteotomy
3. Lateral approach with a partial greater trochanter osteotomy
D. Posterolateral approach with an extended trochanteric osteotomy
Submit Answer
CORRECT ANSWER: D
DISCUSSION:
The patient’s radiographs demonstrate varus femoral remodeling around a broken cylindrical, distally fixed femoral stem. Proximal femoral remodeling around loose or fractured stems occurs in 21% to 42% of femoral revisions, based on the definitions outlined by Foran and associates. In definition 1, varus femoral remodeling occurs when the template falls within 2 mm of the endosteal cortex of the metaphysis on templating with a diaphyseal engaging stem. In definition 2, varus femoral remodeling = when the template crosses the lateral femoral cortex proximally. Based on the templating or drawing a line from the isthmus proximally along the lateral cortex, implantation of a straight stem would perforate the cortex proximally, indicating varus femoral remodeling. An extended trochanteric osteotomy would aid in the removal of the well-fixed distal segment and enable the safe insertion of the new femoral component. The approach is not the concern in this case, because extended trochanteric osteotomies have been described from the posterior and direct lateral approaches with excellent outcomes and union rates. The key is that the extended osteotomy is necessary and not a trochanteric slide or standard (shorter or incomplete trochanteric) osteotomy. These types would not provide access to the well-fixed distal stem, nor would they afford a straight tube in which to insert a new femoral component.
**Question 37** Figures 1 and 2 show the radiograph and CT obtained from a 78-year-old woman who underwent right total hip replacement in 1995. She initially did well with no pain. She was last seen 7 years ago and was having mild hip pain at that time. She was found to have a supra-acetabular cyst on radiographs. She has had severe right hip pain for the past 9 months while using a walker for ambulation. The initial blood work reveals an estimated erythrocyte sedimentation rate of 32 mm/hr, a C-reactive protein level of 0.5 mg/L, a serum cobalt level of 0.4 µg/L, and a serum chromium level of 0.6 µg/L. Right hip aspiration is performed, revealing a white blood cell count of 139, 52% neutrophils, and a negative leukocyte esterase test. What is the best next step?

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1. Acetabular revision, with placement of a custom triflange acetabular component and femoral head exchange
2. Removal of the femoral and acetabular components and placement of an antibiotic spacer, with 6 weeks of intravenous antibiotics
3. Head and liner exchange and retention of the femoral and acetabular implants with acetabular bone grafting
4. Nonsurgical management with the initiation of bisphosphonates and referral to pain management
CORRECT ANSWER: A
DISCUSSION:
The hip replacement was performed in 1995, during the period when the previous generation of polyethylene was utilized. This polyethylene was subjected to irradiation in air, with subsequent oxidation and consequent osteolysis after implantation. The mechanism of osteolysis begins with the uptake of polyethylene particles by macrophages, which then initiate an inflammatory cascade and the release of osteolytic factors. This cycle continues, with eventual implant loosening and failure. The imaging shows significant osteolysis and raises concern for pelvic discontinuity and acetabular implant failure. The surgical treatment consists of acetabular reconstruction. In this patient, concern exists for discontinuity based on the substantial amount of bone loss and nonsupportive anterior and posterior columns. This scenario requires complex acetabular revision using a custom triflange device, distraction with a jumbo acetabular component, or placement of a porous metal cup/cage construct with augmentation. The laboratory values are not consistent with infection or failure due to metal debris.
**Question 38** Figure below shows a cross-table lateral radiograph obtained from a healthy 56-year-old woman with recurrent hip dislocations 6 months after total hip arthroplasty performed through a posterolateral approach. Each dislocation occurred when she was bending over to put her shoes on or pick something up. She has dislocated four times and has had no pain between dislocations. Abductor strength is 5 out of
5/. The infection work-up is negative. What is the best next step?

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1. Revision of the acetabulum and evaluation of the femoral stem
2. Conversion to a constrained liner
3. Gluteus medius repair and application of a hip abductor brace
4. Revision to an elevated acetabular polyethylene liner
CORRECT ANSWER: A
DISCUSSION:
The cross-table lateral radiograph shows that the patient has decreased acetabular anteversion. She is likely impinging on her cup in flexion and levering the femoral component posteriorly. Given a well-fixed and well-aligned femoral component and a negative infection work-up, the preferred treatment is to revise the acetabulum with a goal of increasing acetabular anteversion to avoid prosthetic impingement. Conversion to a constrained or elevated rim liner is suboptimal in this setting, because the problem is impingement. Indications for a constrained liner are neuromuscular compromise, abductor deficiency, or instability despite well-fixed and well-placed components. Given her 5 of 5 abductor strength, gluteus medius repair is not indicated.
**Question 39** Figures below show the radiographs obtained from a 75-year-old woman who underwent right total hip arthroplasty in 2009. She did well until last month, when a right posterior hip dislocation occurred after she fell from her bed to the floor. Successful closed reduction was performed. She sustained two more posterior dislocations requiring closed reduction under anesthesia. The surgical report from the index arthroplasty notes a 54-mm monoblock acetabular component with a 28-mm inner diameter compression molded polyethylene and a high offset neck cementless stem with a +8-mm length, 28-mm head. What is the best next step?

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1. Hip spica cast placement
2. Acetabular revision arthroplasty
3. Resection arthroplasty
4. Femoral head revision to a 28-mm diameter, +10-mm length head
CORRECT ANSWER: B
DISCUSSION:
This patient has demonstrated recurrent instability, and her current implants lack the modularity to upsize and improve the head-neck ratio and range to impingement. Given the monoblock acetabular component and a +7-mm neck length, the best option is revision to a large-diameter femoral head or dual-mobility component. Placement of a hip spica cast and resection arthroplasty are unreasonable. Revision to a longer ball length likely would not solve this recurrent instability pattern.
**Question 40** According to Musculoskeletal Infection Society (MSIS) guidelines, which set of patient laboratory study results fits the definition of chronic prosthetic joint infection?
D. ESR 25 mm/hr, CRP 7 mg/L, joint aspiration WBC count 252, 82% neutrophils, and negative leukocyte esterase
1. Erythrocyte sedimentation rate (ESR) 50 mm/hr, C-reactive protein (CRP) 8 mg/L, joint aspiration white blood cell (WBC) count 542, 62% neutrophils, and positive leukocyte esterase
2. ESR 42 mm/hr, CRP 12 mg/L, joint aspiration WBC count 3,540, 72% neutrophils, and positive leukocyte esterase
3. ESR 20 mm/hr, CRP 15 mg/L, joint aspiration WBC count 4,135, 54% neutrophils, and negative leukocyte esterase
CORRECT ANSWER: B
DISCUSSION:
The MSIS definition of periprosthetic joint infection was updated in 2014 with two major and six minor criteria. The presence of one major criterion or three minor criteria is diagnostic for infection. The major criteria are two positive cultures with the same organism or a draining sinus tract. The current MSIS minor criteria are 1) an elevated ESR (more than 30 mm/hr) and CRP level (more than 10 mg/L), 2) an elevated synovial WBC count (more than 3,000 cells per/microliter), 3) an elevated synovial fluid polymorphonuclear count (more than 80%), 4) a positive histological analysis of periprosthetic tissue, and 5) a single positive culture.
**Question 41** Figures below show the AP and lateral radiographs obtained from a 54-year-old woman who has worsening groin pain 18 months after a primary left total hip arthroplasty. The pain is worst when climbing stairs, when rising from a seated position, and during resisted hip flexion. Her pain improved early after surgery but did
not completely resolve. Her C-reactive protein and erythrocyte sedimentation rate results of less than 1 mg/dL and 10 mm/hr, respectively, were obtained in the office. What is the best next step?

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1. MRI with MARS of the left hip
2. Revision of the left acetabular component
3. Intra-articular ultrasound-guided left hip injection
4. Physical therapy for the left hip
CORRECT ANSWER: B
DISCUSSION:
Iliopsoas impingement is a potential cause of persistent groin pain after a total hip arthroplasty. This patient’s history gives groin pain with resisted hip flexion and during activities that require this level of function. The radiographs depict an acetabular component with substantial retroversion. Typical options for the management of iliopsoas tendon impingement include injections, tenotomy, and acetabular revision. Recently, Chalmers and associates reported more predictable groin pain resolution with 8 mm or more of anterior acetabular component when overhang was revised. The radiographs clearly show more retroversion, with a cup prominence of more than 8 mm anteriorly. MRI with MARS could potentially help in the diagnosis of this impingement but would not help in management (option A). An ultrasound-guided injection would need to be administered into the iliopsoas tendon sheath to be of help and, in this case, would likely be performed for diagnostic purposes due to the extreme anterior overhang (option C). Option D would be useful for mild cases of iliopsoas impingement but likely would not help much in this more extreme case.
**Question 42** Figure 1 shows the radiograph obtained from a 67-year-old man recently diagnosed with osteoarthritis, 8 years after receiving a left metal-on-metal total hip arthroplasty (THA). The acetabular component has a modular cobalt alloy acetabular liner. The patient states that he did very well postoperatively, but for the last 6 months has noted worsening pain and swelling in his left hip. Serum metal ion testing reveals a chromium level of 12.4 ng/mL, compared with a normal level of less than 0.3 ng/mL, and a cobalt level of 11.8 ng/mL, compared with a normal level less than 0.7 ng/mL. An MRI with metal artefact reduction sequence (MARS) was performed and is shown in Figure 2. What is the most appropriate management at this time?

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A. Annual monitoring of serum metal ion levels
1. Repeated MRI with MARS in 6 months
2. Conversion of the THA to a cobalt alloy femoral head and polyethylene bearing
3. Conversion of the THA to a ceramic femoral head with an inner titanium sleeve and polyethylene bearing
CORRECT ANSWER: D
DISCUSSION:
Metal-on-metal THA was initially introduced in the 1990s, with the proposed advantages of decreased wear and improved stability. However, catastrophic adverse local tissue reactions associated with their use has raised numerous concerns. The work-up of a patient with a prior metal-on-metal total hip arthroplasty involves a thorough history and physical examination; blood analysis, including the erythrocyte sedimentation rate, C-reactive protein, and metal ion levels; and secondary imaging, including ultrasonography, CT, and MRI. In a patient with clinical symptoms, elevated metal ion levels, and a large fluid collection seen on MRI, the most appropriate treatment would be removal of the metal-on-metal bearing. Given the presence of an adverse reaction involving cobalt and chromium, a revision ceramic head may be most appropriate to avoid the potential of trunnion-associated corrosion.
**Question 43** Figures below depict the radiographs obtained from a 76-year-old woman with a painful total knee arthroplasty. She describes an uneventful recovery with no wound-healing issues and was pain free for the first 10 years. Although reporting no trauma or inciting event, she now describes pain in the entire knee that is most severe with her first few steps. She has begun to notice night pain and, more recently, constant swelling. What is the most appropriate work-up at this time?

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1. Knee aspiration with cell count/cultures, C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR), CT
2. Knee aspiration with cell count/cultures, CRP, ESR
3. Fresh-frozen specimen at the time of revision knee arthroplasty only
4. Technetium-99m bone scan, knee aspiration with cell count/cultures
CORRECT ANSWER: B
DISCUSSION:
An evaluation of the painful total knee must be supported by an understanding of the potential etiologies of pain. They may include, aseptic loosening, infection, osteolysis, gap imbalance, referred pain, stiffness, and complex regional pain syndrome. In this case, the patient demonstrates start-up pain and had no prior history of infections. Her radiographs show subsidence of the tibia, indicating a loose prosthesis. Knowing that the prosthesis is already loose precludes the need for a bone scan. It is, however, important to rule out infection in this case; therefore, CRP and ESR testing is essential. Aspiration is also recommended when going into knee arthroplasty, and infection is a concern.
**Question 44** The direct anterior (Smith-Peterson) approach to hip arthroplasty is most commonly associated with injury to what nerve?
1. Lateral femoral cutaneous
2. Sciatic
3. Pudendal
4. Superior gluteal
CORRECT ANSWER: A
DISCUSSION:
Some authors have reported the incidence of lateral femoral cutaneous nerve neuropraxia following hip arthroplasty with the direct anterior approach to be near 80%, but resolution of the sensory deficits has been observed in most patients over time. Femoral nerve palsy has been reported to occur in .64% to 2.3% direct lateral (Hardinge) and anterolateral (Watson-Jones) approaches, and the superior gluteal nerve may be injured with proximal extension of the abductor muscular dissection. The posterior approach has been reported to be associated with sciatic nerve injury, especially in cases of dysplasia. Pudendal nerve injury has not been reported with the anterior, anterolateral, direct lateral, or posterior approaches to hip
arthroplasty. It has been reported following hip arthroscopy and the use of a traction table, however.
**Question 45** A 55-year-old woman is referred for evaluation of a painful knee replacement. She underwent total knee arthroplasty (TKA) more than 1 year ago without perioperative complications but has had consistent pain since the surgery. The patient’s preoperative radiographs and postoperative radiographs are shown in Figures below. Examination reveals medial laxity during valgus stress testing and range of motion of 0° to 70°. Her erythrocyte sedimentation rate and C-reactive protein level are normal. What is the best next step?

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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/563538F1-1543610007742.jpg)
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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/563538F1-1543610007742.jpg)
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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/563538F1-1543610007742.jpg)
1. Unloader brace
2. Distal femoral osteotomy
3. Open arthrofibrosis debridement with lateral ligament balancing and polyethylene exchange
4. Revision TKA of both the femoral and tibial components
CORRECT ANSWER: D
DISCUSSION:
The radiographs show substantial valgus malalignment of the femoral component, with lateral mechanical axis deviation. Clinically, by examination she displays instability and stiffness as a result. Revision knee replacement is appropriate and should consist of total revision to stemmed femoral and tibial components with a varus-valgus constrained insert, given the likely attenuation of the medial collateral ligament. Open debridement with ligament balancing and polyethylene exchange do not address the underlying cause and are inappropriate. Distal femoral osteotomy is not useful in the setting of previous total knee replacement. Nonsurgical treatment with an unloader brace would be ineffective in correcting the alignment.
**Question 46** A 45-year-old man has a draining sinus and recurrent infection of his right total knee arthroplasty. He has had two prior revision surgeries after the primary procedure and three other surgeries before his initial replacement, including a proximal tibial osteotomy and subsequent hardware removal. On clinical examination, he has a draining sinus in the mid portion of his surgical scar and a range of motion of 5° to 85°. AP and lateral radiographs of the right knee are shown in Figures below. During surgery, the femoral component is found to be grossly loose, but the tibial component is well fixed. What is the most appropriate extensile approach that would provide adequate exposure and aid in tibial component extraction?

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1. Extended medial parapatellar approach
2. Quadriceps snip
3. Extended tibial tubercle osteotomy
4. Medial epicondyle osteotomy
CORRECT ANSWER: C
DISCUSSION:
Extended tibial tubercle osteotomy is an extensile approach to revision total knee arthroplasty that affords excellent exposure and can facilitate removal of tibial sleeves and cones. This patient has had multiple surgeries, including a proximal tibial osteotomy, as well as poor range of motion, patella baja, and a well-fixed metaphyseal sleeve component. Classically, an extended tibial tubercle osteotomy provides outstanding exposure for component removal in the setting of prior high tibial osteotomy and patella baja. For this patient, it is important to recognize the patella baja on the radiographs, as well as the tibial sleeve. In many of these cases the osteotomy provides access to the sleeve to help with extraction, because the stem will not pull through the sleeve or detach from the tray to allow visualization of the sleeve. The extended medial parapatellar approach is just a long medial approach that typically yields good exposure
but would not help with the patella baja or extraction of the tibial sleeve. The quadriceps snip would give good exposure to the knee but would not aid in tibial component removal. Lastly, the medial epicondyle osteotomy could help with exposure and tensioning of the medial complex of the knee but would not help with tibial component extraction.
**Question 47** A 58-year-old woman underwent a left total knee arthroplasty 6 years ago. She initially did well after surgery but sustained a fall 2 months ago while at work. She now describes left knee pain and instability and an inability to straighten her knee since the fall. She has been using a hinged knee brace, which provides partial support. On examination, she has passive range of motion of 0° to 115° and active range of motion of 80° to -115°. Her radiographs are shown in Figures below. What is the best option for the restoration of her function?

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1. Revision total knee arthroplasty with placement of a hinge constrained device
2. Patellar tendon repair with nonabsorbable suture and patellar resurfacing
3. Hinged knee brace with drop lock design to restore stability during ambulation
4. Extensor mechanism reconstruction using synthetic mesh or allograft
CORRECT ANSWER: D
DISCUSSION:
The patient has an extensor mechanism disruption with patellar tendon rupture. This injury is treated with extensor mechanism reconstruction in the setting of previous total knee arthroplasty. There is a reported high failure rate with attempted repair. Revision to hinge knee arthroplasty would provide implant stability but would not restore the extensor mechanism. The patient is relatively young and is working, so reconstruction would offer better long-term function than a drop lock brace, which can be better used in low-functioning patients with this type of injury. Extensor mechanism reconstruction historically has been accomplished with allograft material, but a novel technique using synthetic mesh also has proved successful in treating this difficult problem.
**Question 48** Figures below show the radiographs, and the CT obtained from a 58-year-old woman who underwent cementless left total hip arthroplasty. Nine months after surgery, she continued to have groin pain when actively flexing her hip. She has trouble walking up stairs and getting out of her car.
What is the most likely diagnosis?

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1. Trochanteric bursitis
2. Femoral component loosening
3. Iliopsoas tendonitis
4. Acetabular component loosening
CORRECT ANSWER: C
DISCUSSION:
Groin pain after total hip replacement has a number of possible causes, and an exact diagnosis may remain elusive in some patients. Infection should be ruled out with laboratory studies and, if indicated, diagnostic aspiration of the hip joint. Implant loosening should be evaluated by plain radiograph and bone scan, if indicated. Synovitis resulting from wear debris should be considered in patients with polyethylene liners who experience late-onset symptoms or in any patient with a metal-on-metal bearing. This patient's symptoms are classic for iliopsoas tendonitis. Physical examination usually reveals pain and weakness with resisted hip flexion. A cross-table lateral radiograph and CT show that the anterior edge of the acetabulum protrudes beyond the anterior wall, thereby acting as a source of iliopsoas tendon irritation. In such cases, acetabular component revision and repositioning are indicated. Fluoroscope-guided iliopsoas cortisone injection can help to establish the diagnosis and relieve groin pain. If the acetabular component is well positioned, then iliopsoas tenotomy should be considered.
**Question 49** A 72-year-old woman is scheduled to undergo right total hip arthroplasty. Her preoperative radiograph is shown in Figure below. To avoid increasing this patient’s combined offset while maintaining her leg length, what is the most appropriate surgical plan?

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1. Lateralize the acetabular component, use a low offset femoral component, and make a shorter neck cut
2. Medialize the acetabular component, use a low offset femoral component, and make a longer neck cut
3. Lateralize the acetabular component, use a high offset femoral component, and make a shorter neck cut
4. Medialize the acetabular component, use a high offset femoral component, and make a longer neck cut
CORRECT ANSWER: B
DISCUSSION:
The management of patients with proximal femoral deformity can be difficult. Appropriate implant selection and preoperative templating are critical. In this patient, it would be difficult to avoid increasing the combined offset by too much, which could contribute to the overtensioning of the soft tissues and trochanteric pain. By medializing the acetabular component (decreasing the combined offset), using a low offset femoral component or a cemented component placed more valgus (decreasing the combined offset), and making a longer neck cut (to avoid shortening of the lower extremity), restoration of the patient’s native offset and leg length can be achieved.
**Question 50** Figures below demonstrate the radiographs obtained from a 56-year-old man with a 3-year history of right groin pain. A comprehensive nonsurgical program has failed, and the patient would like to proceed with total hip arthroplasty. He is seen by a pain management specialist and is currently taking 40 mg of sustained-release morphine twice daily with oxycodone 10 mg 2 to 3 times a day for severe pain. What is the recommended course of action regarding his chronic narcotic use?

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D. Stop all his opioids 5 days before surgery, and place the patient on a morphine pain control pump postoperatively with a basal rate.
1. Increase his current opioid medication regimen prior to and after surgery as needed to control his pain.
2. Decrease his preoperative opioid use, and work with his pain management physician to decrease his postoperative opioid requirement.
3. Avoid using narcotics in the perioperative period to prevent overdose, and use acetaminophen only for pain control.
CORRECT ANSWER: B
DISCUSSION:
Chronic opioid consumption prior to total joint arthroplasty has been associated with increased pain after surgery, increased opioid requirements, a slower recovery and longer hospital stay, and higher 90-day postoperative complications compared with patients not on chronic opioids preoperatively. Based on this information, Nguyen and associates performed a study in three patient groups that included 1) chronic opioid users who underwent no preoperative intervention, 2) chronic opioid users who were weaned down to 50% of their prior opioid regimen, and 3) patients who were not chronic opioid users. The authors found that the reduction of preoperative opioid use improved postoperative function, pain, and recovery and that the weaned group performed more like the opioid naive group than the chronic opioid user
group. Increasing opioid use prior to surgery in this patient would make it more difficult to control pain after surgery. Stopping all of his opioids just prior to surgery would place the patient at substantial risk for opioid withdrawal and is not recommended. Avoiding the use of all narcotics and using only acetaminophen postoperatively is very unlikely to provide appropriate pain relief in a chronic opioid user. The recommendation based on the provided literature is to decrease the patient's narcotic use prior to surgery.
**Question 51** A 72-year-old patient fell 3 weeks after undergoing a total hip arthroplasty using cementless fixation of the femoral component. She sustained a comminuted Vancouver type B-2 fracture with displacement of the calcar fragment. What is the best treatment option?
1. Revision using a proximal femoral replacement prosthesis
2. Revision using a diaphyseal engaging femoral prosthesis along with cerclage fixation
3. Open reduction internal fixation using a locking plate with strut graft
4. Protected weight bearing with abduction bracing
CORRECT ANSWER: B
DISCUSSION:
The patient has an acute postoperative fracture of the proximal femur with subsidence. It is also common that the stem retroverts relative to the femur. It is most often seen in proximally porous coated stems within 90 days of surgery, one paper found it to occur 0.7% of the time in modern implants. There is always a debate whether this is a missed intraoperative fracture, or a new fracture that has resulted from an event of increased hoop stresses. Removal of the primary stem, placement of a diaphyseal engaging stem (most frequently a tapered-fluted stem), and cabling of the fracture is the most successful treatment.
**Question 52** What is the most important preoperative factor predicting conversion to total hip arthroplasty after arthroscopic surgery of the hip?
1. Age over 60 years
2. Morbid obesity
3. Diagnosis of osteoarthritis
4. Tobacco use
CORRECT ANSWER: B
DISCUSSION:
The authors cited in the

Scientific References

examined large databases to determine the risk factors for conversion to total hip arthroplasty after arthroscopic surgery of the hip. In the study by Kester and associates, obesity had an odds ratio (OR) of 5.6 for conversion to hip arthroplasty, whereas age over 60 years had an OR of 3.4, osteoarthritis had an OR of 2.4, and tobacco use had an OR of 1.9.
**Question 53** A 70-year-old woman with a body mass index (BMI) of 34 and a history of hypercholesterolemia has elected to undergo total hip arthroplasty. Her son recently learned he has factor V Leiden following an episode of pulmonary embolism. What are this patient's risk factors for thromboembolic disease?
1. Type of surgery, age, and BMI
2. Type of surgery, hypercholesterolemia, and age
1. Age, BMI, and hypercholesterolemia
2. BMI, type of surgery, and hypercholesterolemia
CORRECT ANSWER: A
DISCUSSION:
Risk stratification is one of the most critical clinical evaluations to undertake before performing total joint arthroplasty. Many factors have been identified that increase the risk for venous thromboembolism (VTE) The major factors include previous VTE, obesity, type of surgery (such as total joint arthroplasty), hypercoagulable states, myocardial infarction, congestive heart failure, family history of VTE, and hormone replacement therapy. Hypercholesterolemia is not a risk factor for thromboembolic disease.
**Question 54** Figures below depict the radiographs obtained from a 76-year-old woman who comes to the emergency department after experiencing a fall. She is an unassisted community ambulator with a history of right hip pain. What is the most appropriate surgical treatment for this fracture?

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1. Cemented unipolar hemiarthroplasty
2. Cemented bipolar hemiarthroplasty
3. Total hip replacement
4. Open reduction and internal fixation
CORRECT ANSWER: C
DISCUSSION:
This patient has pre-existing right hip osteoarthritis. The most correct option for the treatment of this active patient is a right total hip arthroplasty. Hemiarthroplasty would not address the patient's pain from osteoarthritis, and open reduction and internal fixation would not fix the femoral head issue or the osteoarthritis.
**Question 55** Figures below show the clinical photograph and radiograph obtained from a 62-year-old man who has deformity and pain 1 year after primary total hip arthroplasty. What is the reason for the observed deformity?

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1. A Vancouver type B1 fracture
2. Residual leg-length discrepancy
3. Loosening and subsidence of the femoral stem into anteversion
4. Loosening and subsidence of the femoral stem into retroversion
CORRECT ANSWER: D
DISCUSSION:
Figure 1 reveals an external rotation deformity of the right lower extremity. This deformity can have numerous causes, including extra-articular deformity. Figure 2 reveals a loose, subsided femoral component. Femoral stems typically subside into retroversion due to proximal femoral biomechanics, which cause a compensatory external rotation deformity. The combined findings from both images suggest an external rotation deformity most likely related to subsidence into retroversion.
**Question 56** Figures below show the radiographs obtained from an 86-year-old-woman who has had chronic left hip pain for several years. She now uses a walker and a wheelchair for ambulation. She is medically healthy. What is the most appropriate surgical intervention?

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1. Cemented left total hip arthroplasty (THA)
2. Cementless left THA with a proximally porous coated femoral stem
3. Hybrid left THA
4. Cementless left THA with a diaphyseal engaging conical femoral stem
CORRECT ANSWER: C
DISCUSSION:
This 86-year-old woman has poor bone quality and osteoarthritis of the left hip. Her lateral radiograph confirms Dorr type C bone quality. A hybrid left THA with a cemented femoral stem would be the treatment of choice.
**Question 57** Figure below shows the radiograph obtained from a 76-year-old woman who has sharp pain in her groin, thigh, and buttocks that worsens with activity. She has been dealing with this pain for more than a year but is otherwise healthy. Recently, she has begun to notice night pain. The pain no longer responds to NSAIDs. She would like to be able to dance at her daughter's wedding in 4 months and wonders how best to proceed. What is the best next step?

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1. Radiograph-guided steroid injection followed by total hip arthroplasty 6 weeks later
2. Total hip arthroplasty
3. Physical therapy
4. Referral back to her spine surgeon
CORRECT ANSWER: C
DISCUSSION:
The next best course of action is total hip arthroplasty. The patient is an otherwise healthy woman requesting pain relief and expresses a desire to be dancing in 4 months. She has had more than 6 months of symptoms that are classic hip osteoarthritis symptoms, with pain in the groin and thigh. Severe osteoarthritis is seen in the radiograph as well. NSAIDs are no longer working. Given the objective findings, the subjective reports, and the duration of symptoms, this patient merits surgery. Consideration for steroid injection is reasonable, but given her desire to be dancing in 4 months, an injection would increase her risk of infection if total hip arthroplasty were to be performed within 3 months of the injection.
**Question 58** A 68-year-old woman underwent an uncemented medial/lateral tapered femoral placement during a total hip arthroplasty. The orthopaedic surgeon noticed a nondisplaced vertical fracture in the calcar region of the femoral neck during final implant insertion. What is the most appropriate treatment?
1. Removal of the press-fit implant and cementing of the same femoral stem
2. Removal of the uncemented femoral component and placement of a revision modular taper-fluted femoral stem
3. Removal of the implant, placement of a cerclage wire around the femoral neck above the lesser trochanter, and reinsertion of the implant
4. Final seating of the uncemented femoral component without additional measures
CORRECT ANSWER: C
DISCUSSION:
The recognized treatment for a proximal periprosthetic fracture is to first identify the extent and then optimize the correction of the fracture. Several studies indicate that proximal cerclage wiring is adequate to create "barrel hoop" stability of the proximal femur. Braided cables offer superior stability compared with twisted wires or Luque wires. Finally, the appropriate postoperative treatment is protected
weight bearing for 6 weeks, with periodic radiographs taken at 2-week intervals. Other options such as cementing the femoral stem and using a revision arthroplasty device are indicated for unstable fractures.
**Question 59** Injury to the popliteal artery during total knee arthroplasty (TKA) is most likely to occur when placing a sharp retractor
1. directly posterior to the posterior cruciate ligament (PCL).
2. posteromedial to the PCL.
3. posterolateral to the PCL.
4. in the posteromedial corner of the knee.
CORRECT ANSWER: C
DISCUSSION:
Vascular complications during TKA are rare but do occur. Traditionally, it was taught that the popliteal artery was situated posterior to the PCL; however, more recent anatomic dissections have demonstrated that this artery is usually located posterolateral to the PCL.
**Question 60** A 70-year-old woman has a 3-year history of gradually increasing diffuse and global right knee pain. Her main issues are difficulty with stairs, stiffness with prolonged sitting, and swelling. She has taken NSAIDs and has received intra-articular steroid injections, all with decreasing efficacy. Her right knee examination reveals a range of motion of 15° to 80° with a fixed deformity to varus and valgus stress. Her symptoms are no longer manageable nonsurgically. Radiographs reveal a 30-degree mechanical axis deformity. When using the measured resection technique during total knee arthroplasty (TKA), the best way to avoid femoral malrotation is to reference the
1. anteroposterior axis.
2. tibial intramedullary axis.
3. posterior condylar axis.
4. femoral intramedullary axis.
CORRECT ANSWER: A
DISCUSSION:
In the setting of valgus deformities, TKA poses different challenges than those encountered when varus deformities are present. Most valgus alignment is attributable to a deformity of the distal femur rather than of the proximal tibia, as seen in varus knees. One of the major anatomical differences is a hypoplastic lateral femoral condyle which, when not recognized and used as a rotational reference point, can lead to internal rotation of the femoral component. This malrotation in turn leads to patellofemoral maltracking or instability, which is a common complication associated with primary TKA.
**Question 61** A 70-year-old woman has a 3-year history of gradually increasing diffuse and global right knee pain. Her main issues are difficulty with stairs, stiffness with prolonged sitting, and swelling. She has taken NSAIDs and has received intra-articular steroid injections, all with decreasing efficacy. Her right knee examination reveals a range of motion of 15° to 80° with a fixed deformity to varus and valgus stress. Her symptoms are no longer manageable nonsurgically. Radiographs reveal a 30-degree mechanical axis deformity. The deformity shown in Figure below is predominantly associated with

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1. a hypoplastic lateral femoral condyle.
2. a contracted medial collateral ligament.
3. an excessive proximal tibial slope.
4. trochlear dysplasia.
CORRECT ANSWER: A
DISCUSSION:
In the setting of valgus deformities, TKA poses different challenges than those encountered when varus deformities are present. Most valgus alignment is attributable to a deformity of the distal femur rather than of the proximal tibia, as seen in varus knees. One of the major anatomical differences is a hypoplastic lateral femoral condyle which, when not recognized and used as a rotational reference point, can lead to internal rotation of the femoral component. This malrotation in turn leads to patellofemoral maltracking or instability, which is a common complication associated with primary TKA.
**Question 62** Figures below show the radiographs, and the MRIs obtained from a 32-year-old man with worsening left knee pain. A 3-foot hip-to-ankle radiograph shows a 13-degree varus knee deformity. The patient sustained a major left knee injury 5 years ago and a confirmed complete anterior cruciate ligament (ACL) tear. He managed this injury nonsurgically with a functional brace but experienced worsening pain. He was seen by an orthopaedic surgeon 18 months ago, and a medial meniscus tear was diagnosed; the tear was treated with an arthroscopic partial medial meniscectomy. Since then, his knee has been giving way more often, and he no longer feels safe working on a pitched roof. The patient received 6 months of formal physical therapy and was fitted for a new functional ACL brace, but he still has pain and instability. He believes he has exhausted his nonsurgical options and would like to undergo surgery. What is the most appropriate treatment at this time?

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1. ACL reconstruction and subsequent proximal tibial osteotomy
2. ACL reconstruction alone
3. Distal femoral osteotomy with simultaneous ACL reconstruction
4. Proximal tibial osteotomy with subsequent ACL reconstruction
CORRECT ANSWER: D
DISCUSSION:
Proximal tibial osteotomy is the most appropriate intervention to correct varus malalignment and to reduce stress on the ACL. In some cases, proximal tibial osteotomy alone may address both pain and instability, but if instability persists, particularly in the setting in which instability can be dangerous, subsequent ACL reconstruction can further stabilize the knee with less stress on the graft after the correction of malalignment. Varus alignment places increased stress on the native or reconstructed ACL. ACL reconstruction should be performed only at the same time as or following proximal tibial osteotomy to correct alignment in the setting of varus malalignment. It is not appropriate to perform ACL reconstruction prior to proximal tibial osteotomy in this setting. Distal femoral osteotomy is not indicated to correct varus malalignment. Varus alignment places increased stress on the native or reconstructed ACL, and ACL reconstruction alone is not indicated for this patient.
**Question 63** When balancing gaps in the coronal plane, what structure preferentially impacts the flexion space more than the extension space?
1. Iliotibial band
2. Popliteus tendon
3. Lateral collateral ligament
4. Lateral head of the gastrocnemius
CORRECT ANSWER: B
DISCUSSION:
In the setting of valgus deformities, TKA poses different challenges than those encountered when varus deformities are present. Most valgus alignment is attributable to a deformity of the distal femur rather than of the proximal tibia, as seen in varus knees. One of the major anatomical differences is a hypoplastic lateral femoral condyle which, when not recognized and used as a rotational reference point,
can lead to internal rotation of the femoral component. This malrotation in turn leads to patellofemoral maltracking or instability, which is a common complication associated with primary TKA.
**Question 64**
A 45-year-old woman has severe anterior knee pain. Her radiographs indicate end-stage patellofemoral
compartment osteoarthritis. The tibiofemoral compartments are preserved. Extensive nonsurgical treatment has failed to provide relief, and she is offered patellofemoral arthroplasty (PFA). What is the most common long-term mode of failure for PFA using an implant with an onlay prosthesis design?
1. Infection
2. Patellar instability
3. Aseptic loosening
4. Progression of tibiofemoral arthritis
CORRECT ANSWER: D
DISCUSSION:
Contemporary onlay-design trochlear prostheses in PFA replace the entire anterior trochlear surface. Previous inlay designs were inset within the native trochlea and carried a higher risk of catching and patellar instability, particularly in patients with trochlear dysplasia; they also generally have higher failure rates. The current most common mode of failure is progression of arthritis throughout the knee, in some series as high as 25% at 15 years. Aseptic loosening, particularly of cemented implants, is less common. Infection is an uncommon long-term complication. Patients considering PFA should be advised of the risk of arthritis progression. Many authors routinely obtain a preoperative MRI to assess the status of the tibiofemoral compartments.
**Question 65** Figures below show the radiographs obtained from a 79-year-old woman who has been experiencing increasing tibial pain 10 years after undergoing revision total knee arthroplasty. No evidence of infection is seen. What is the most appropriate treatment?

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1. Retain the components, and implant a tibial strut allograft.
2. Revise the tibial component with a metaphyseal cone and metaphyseal uncemented stem.
3. Revise the tibial component with a metaphyseal cone and a press-fit diaphyseal-engaging stem.
4. Revise the tibial component with a long cemented diaphyseal-engaging stem.
CORRECT ANSWER: C
DISCUSSION:
Stems are available for cemented and press-fit implantation. To be effective, press-fit stems should engage the diaphysis, as shown in Figures 3 and 4. They also assist in obtaining correct limb alignment. Short metaphyseal-engaging stems are associated with failure rates that range between 16% and 29%. Cemented stems may be shorter than press-fit stems, because they do not have to engage the diaphysis. Short, fully cemented stems offer the advantage of metaphyseal fixation. Hybrid stem fixation makes use of the metaphysis for cement fixation with metaphyseal cones or sleeves and diaphyseal-engaging press-fit stems.
**Question 66** A 70-year-old man reports symptomatic medial knee pain that has become progressively worse during the past year. MRI reveals a complex, posterior horn medial meniscus tear with associated medial lateral and patellofemoral cartilage defects. Radiographs reveal medial joint space narrowing and osteophytes in the other compartments. What treatment is most likely to provide long-term, durable relief of symptoms?
1. High tibial osteotomy
2. Total knee replacement
3. Unicondylar knee replacement
4. Arthroscopic partial meniscectomy
CORRECT ANSWER: B
DISCUSSION:
Total knee replacement is a well-established surgery for diffuse, symptomatic osteoarthritis of the knee joint, and its efficacy has been shown in many studies. According to the 2008 AAOS Clinical Practice Guideline, Treatment of Osteoarthritis of the Knee, arthroscopy in the setting of existing osteoarthritis is efficacious for relieving the signs and symptoms of a torn meniscus but not for osteoarthritis. Likewise, in young and active patients, clinical outcomes show improvement after realignment osteotomy for single-compartment osteoarthritis. Unicondylar knee replacement is not indicated for tricompartmental disease of the knee.
**Question 67** A 58-year-old man with insulin-dependent diabetes mellitus underwent primary total knee arthroplasty (TKA). A full-thickness skin slough measuring 3 cm by 4 cm developed, with postsurgical exposure of the patellar tendon. No change is observed in the appearance of the wound after 2 weeks of wet-to-dry dressing changes. What is the best next treatment step for the soft-tissue defect?
1. Continued dressing changes
2. Split-thickness skin graft
3. Full-thickness skin graft
4. Local rotational flap
CORRECT ANSWER: D
DISCUSSION:
If wound healing does not occur and deep soft tissues such as the patellar tendon are exposed following TKA, local rotational flap is the procedure of choice. The procedure should be performed relatively early after the recognition of a soft-tissue wound-healing problem. In the setting of TKA, the gastrocnemius muscle is an excellent source of flaps for wound coverage of the proximal tibia.
**Question 68**
A 77-year-old man who underwent right total knee replacement surgery 2 and a half years ago has had knee pain since surgery. The pain is diffuse, constant, and made worse with activity. He notes warmth and swelling in his knee. Examination shows a well-healed incision, no erythema, moderate warmth, synovitis, and an effusion. The knee is stable, and has an arc of flexion between 3° and 120°. Radiographs show well-fixed and well-aligned implants. What is the most appropriate initial treatment?
1. Knee aspiration for culture
2. CT of the knee to assess implant rotation
3. Indium-111 leukocyte/technetium-99m sulfur colloid scan of the knee
4. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) laboratory studies
CORRECT ANSWER: D
DISCUSSION:
This patient's history and physical findings are concerning for deep infection. Inflammatory markers, including ESR and CRP, should be obtained first. If the levels are elevated, knee aspiration should be performed for the synovial cell count and culture. A bone scan is not indicated in an initial investigation for deep infection; it is rarely helpful and is not cost effective. CT to assess implant rotation is an appropriate investigation for knee pain when the clinical scenario is not suspicious for a deep infection and when infection has been excluded.
**Question 69** A 61-year-old man with a body mass index of 31 had a 6-month gradual onset of right medial knee pain. Examination revealed a small effusion, stable ligaments, a normally tracking patella, and mild medial joint line tenderness. Standing radiographs show mild medial joint space narrowing. Effective treatment at this stage of early medial compartmental osteoarthritis includes
1. glucosamine 1,500 mg/day and chondroitin sulfate 800 mg/day.
2. weight loss through dietary management and low-impact aerobic exercises.
3. arthroscopic debridement and lavage.
4. a valgus-directing brace.
CORRECT ANSWER: B
DISCUSSION:
According to the 2008 AAOS Clinical Practice Guideline, Treatment of Osteoarthritis of the Knee (Nonarthroplasty), level 1 evidence confirms that weight loss and exercise benefit patients with knee osteoarthritis. The other responses have either inclusive evidence (a valgus-directing brace) or no evidence to support their use (glucosamine 1,500 mg/day and chondroitin sulfate 800 mg/day as well as arthroscopic debridement and lavage).
**Question 70** In patients with Crowe types III and IV developmental dysplasia of the hip with high hip centers, acetabular reconstruction often requires lowering the acetabular component into the native acetabulum. In doing so, considerable risk for limb lengthening beyond 4 cm exists, making the hip difficult to reduce and raising the risk for nerve injury. Which technique is used to overcome this problem?
1. Subtrochanteric osteotomy with femoral shortening
2. An offset femoral component
3. A lateralized liner
4. Extended trochanteric osteotomy
CORRECT ANSWER: A
DISCUSSION:
When substantial lengthening of a dysplastic hip will occur because a high dislocation is relocated into a considerably lower acetabulum, a femoral shortening may be necessary to reduce the hip and avoid a stretch injury to the sciatic nerve. No other choice specifically addresses the need for femoral shortening, and high offset stems and lateralized liners may exacerbate the problem if used alone and without femoral shortening.
**Question 71**
What factor is considered one of the early changes in osteoarthritic cartilage?
1. Decreased water content
2. Increased proteoglycan content
3. Decreased loading of the solid matrix
4. Increased cartilage tissue permeability
CORRECT ANSWER: D
DISCUSSION:
The normal regulation of a cartilage surface is a delicate balance of degradation and synthesis. When this normal regulation of the cartilage is disturbed, a proinflammatory state tips the cellular pathway in the direction of degradation. The proinflammatory state upregulates the production of cytokines and proteolytic enzymes, specifically matrix metalloproteinases. These enzymes attack the proteoglycan content of the cartilage, leading to an overall reduction in the proteoglycan content. This reduction in content leads to increased permeability of the cartilage substrate. With increased permeability, water is able to move into the cartilage itself, thereby increasing the overall water content within the cartilage in an arthritic state. Finally, because of the increased permeability and increased water content, the overall load or pressure placed on the underlying solid matrix is increased. Increased water content, decreased proteoglycan content, and an increased load on the solid matrix are typical of an osteoarthritic process within normal cartilage. Therefore, the only correct option is that the cartilage has an increased amount of permeability in osteoarthritis.
**Question 72** A 47-year-old obese man with a body mass index of 42 comes into the office with left knee pain 1 year after undergoing an uncomplicated left medial unicompartmental knee arthroplasty (UKA). Radiographs show a loose tibial component in varus. What is the most appropriate next step to treat this failed construct?
1. Aspiration of joint fluid to obtain a cell count
2. Revision of the UKA using primary total knee arthroplasty (TKA) components
3. Revision of the UKA using a revision TKA with augments
4. Procurement of the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level
CORRECT ANSWER: D
DISCUSSION:
This patient likely is experiencing failure of the UKA secondary to poor patient selection. In this young, heavy man, the component likely loosened due to the ongoing varus alignment of the knee and his elevated
weight. Despite this likely scenario, the next step is determining whether an infection is the cause of his pain. Prior to obtaining an aspiration, the surgeon can order ESR and CRP studies to determine whether aspiration is warranted. If the laboratory studies are unremarkable, the surgeon likely can forgo the aspiration and proceed to a revision TKA with possible augments on standby.
**Question 73** Figure below shows the standing AP radiograph obtained from a 55-year-old man who has a 5-year history of daily left knee medial joint line pain with weight-bearing activities. He denies night pain or symptoms of instability. On examination, his range of motion is 0° to 140°. He has a mild, fully correctable varus deformity and a negative Lachman test result. Nonsurgical treatment has failed. What is the UKA survivorship for a 55-year-old patient, compared with the survivorship for total knee arthroplasty?

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1. Equal at 10 years
2. Lower at 10 years
3. Higher at 10 years
4. Not known when using a mobile-bearing UKA
CORRECT ANSWER: B
DISCUSSION:
A patient with medial compartment arthritis and a correctable varus deformity with no clinical or examination findings of knee instability most likely has an intact anterior cruciate ligament (ACL). The pattern of medial compartment osteoarthritis most commonly associated with an intact ACL is that of anteromedial osteoarthritis. An incompetent ACL is commonly associated with a fixed varus deformity and radiographic signs of posteromedial wear. An incompetent ACL is a relative contraindication to a mobile-bearing UKA. When evaluating patients for a mobile-bearing UKA, a stress radiograph aids the orthopaedic surgeon in determining the correction of the varus deformity and assessing the lateral compartment. An inability to fully correct the deformity or narrowing of the lateral compartment with valgus stress should influence the surgeon against UKA. Joint registries across the world have shown decreased survivorship associated with TKA and UKA in men compared with other age groups, but survivorship is lower for UKA than for TKA. No studies to date have shown any differences in survivorship between fixed-bearing and mobile-bearing UKAs. The complication that is unique to mobile-bearing UKA is bearing spinout, which occurs in less than 1% of mobile-bearing UKA procedures. In vivo and in vitro polyethylene wear in mobile-bearing UKA are low. Arthritis may progress faster in patients with mobile-bearing UKAs than in those with fixed-bearing UKAs.
**Question 74** A 57-year-old woman experiences pain 1 year after total knee arthroplasty (TKA). She reports sharp anterior pain and a painful catching sensation that is aggravated by rising from a chair or climbing stairs. Physical examination reveals a mild effusion and a range of motion of 2° to 130°, with patellar crepitus.
The symptoms are reproduced by resisted knee extension. Radiographs show a well-aligned posterior-stabilized TKA without evidence of component loosening. What is the most likely cause of this patient's pain?
1. Patellar clunk syndrome
2. Flexion gap instability
3. Polyethylene wear
4. Femoral component malrotation
CORRECT ANSWER: A
DISCUSSION:
Patellar clunk syndrome is caused by the development of a fibrous nodule on the posterior aspect of the quadriceps tendon at its insertion into the patella. It causes a painful catching sensation when the extensor mechanism traverses over the trochlear notch as the knee extends from 45° of flexion to 30° from full extension. It characteristically occurs in posterior stabilized total knee arthroplasties and appears to be related to femoral component design. The syndrome can usually be prevented by excising the residual synovial fold just proximal to the patella. Flexion gap instability can also cause a painful total knee arthroplasty but is less common in posterior stabilized implants. Femoral component malrotation can cause pain attributable to a flexion gap imbalance or patellar tracking problems. Polyethylene wear would be unlikely after just 1 year. Patellar clunk syndrome can usually be addressed successfully with arthroscopic synovectomy. Recurrence is uncommon. Physical therapy may help to strengthen the quadriceps following synovectomy but would not resolve the clunk syndrome symptoms. Femoral or tibial insert revision is not indicated if patellar clunk syndrome is the only problem resulting in a painful
total knee arthroplasty.
**Question 75** In total knee arthroplasty, in vitro testing has shown that cross-linking can diminish the rate of polyethylene wear by 30% to 80%. What other change in material properties is possible when polyethylene is highly cross-linked?
1. Increased ductility
2. Increased wettability
3. Diminished fatigue strength
4. Decreased resistance to abrasive wear
CORRECT ANSWER: C
DISCUSSION:
The most important concern regarding highly cross-linked polyethylene relates to decreased mechanical properties. Cross-linking results in reduced ductility, tensile strength, and fatigue crack propagation resistance. These problems have not been shown to cause implant failure in the most recent clinical trials, but they remain the most important mechanical issues associated with current material processing methods.
**Question 76** A 70-year-old woman who underwent total knee replacement 18 months ago has had 3 weeks of moderate drainage from a previously healed wound. What is the most appropriate treatment?
A. Vacuum-assisted wound closure dressing
1. Intravenous antibiotics for 6 weeks, followed by long-term oral antibiotic administration
2. Irrigation and debridement, followed by polyethylene exchange
3. Two-stage debridement and reconstruction
CORRECT ANSWER: D
DISCUSSION:
This situation represents a definitively and chronically infected knee replacement. Antibiotic therapy alone might suppress the infection but would not eradicate it. Debridement and polyethylene exchange would be appropriate treatment for an early postoperative infection. The treatment of choice is to perform a two-stage debridement and reconstruction. Although not among the listed choices, an aspiration or culture could be done presurgically and might help clinicians identify the best antibiotics to treat the condition. Antibiotic selection would not affect the need for the two-stage reconstruction, however.
**Question 77** During a posterior cruciate ligament (PCL)-retaining total knee arthroplasty, a critical principle to remember is to
1. accurately tension the PCL.
2. use bony resection to adjust the joint line.
3. maintain a small amount of residual deformity.
4. use intraoperative fluoroscopy to ensure femoral roll back.
CORRECT ANSWER: A
DISCUSSION:
Maintenance of the joint line and accurately tensioning the PCL are critical in the proper execution of a PCL-retaining total knee arthroplasty. Appropriate tension helps ensure femoral rollback and avoid stiffness or instability. Raising the joint line to help ensure full extension should be avoided in cruciate-retaining knees, because doing so creates an unfavorable kinematic environment. The three important principles of surgical technique needed to maintain appropriate tensioning of the PCL include 1) choosing the proper femur size to reproduce the native femoral anterior/posterior dimension, 2) reproducing the joint line by resecting as much tibia from the healthy side as will be replaced by the smallest thickness of the tibial component and, 3) ensuring that full extension is achieved by soft-tissue releases and not by taking additional distal femur, as may be done in a posterior stabilized approach. Another important principle is to re-create the natural degree of the patient’s posterior tibial slope to avoid tightness in flexion.
**Question 78** Figures below depict the AP and lateral radiographs obtained from a 64-year-old man with long-standing right knee osteoarthritis and pain that is unresponsive to nonsurgical treatment. The patient undergoes navigated cruciate-retaining right total knee arthroplasty. After surgery, this patient continues to experience pain and swelling of the knee with recurrent effusions. He returns to the office reporting continued pain 2 years after surgery. He describes instability, particularly when descending stairs. On examination, range of motion of 0° to 120° is observed, with no extensor lag. Slope of the tibial component is 7°. The knee is stable to varus and valgus stress in extension, but flexion instability is present in both the anterior-posterior direction and the varus-valgus direction. Bracing leads to a slight decrease in symptoms but is not well tolerated. Isokinetic testing demonstrates decreased knee extension velocity at
mid push. Radiographs demonstrate well-aligned and fixed knee implants. An infection work-up is negative. What is the most appropriate surgical intervention at this time?

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1. Tibial polyethylene exchange
2. Revision of the femoral and tibial components and conversion to a posterior stabilized insert
3. Revision of the femoral and tibial components to a constrained rotating hinge prosthesis
4. Isolated femoral component revision and upsizing of the femoral implant with a new posterior cruciate ligament (PCL)-retaining polyethylene insert
CORRECT ANSWER: B
DISCUSSION:
The patient’s symptoms at follow-up—pain, swelling, and difficulty descending stairs—suggest knee flexion instability. Considering his history, an incompetent PCL must be considered. Revision of the knee to a posterior stabilized or nonlinked constrained condylar implant (depending on the condition of the ligaments) likely is needed to address his symptoms. The difference in extension stability and flexion stability makes polyethylene exchange a poor option. A constrained rotating hinge design is not necessary. Repeat use of a PCL-retaining insert is not recommended. Tibial and femoral revision both are required. Correction of excessive slope will be attained with tibial revision, femoral component revision is required to convert to a PCL-substituting design. There is also an opportunity to increase posterior condylar offset if needed.
**Question 79** Figure below shows the standing AP radiograph obtained from a 55-year-old man who has a 5-year history of daily left knee medial joint line pain with weight-bearing activities. He denies night pain or symptoms of instability. On examination, his range of motion is 0° to 140°. He has a mild, fully correctable varus deformity and a negative Lachman test result. Nonsurgical treatment has failed. Unicompartmental knee arthroplasty (UKA) is discussed with the patient. The most appropriate next radiographic evaluation should be

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1. MRI of the left knee to evaluate the lateral compartment.
2. a CT arthrogram to evaluate the status of the medial and lateral meniscus.
3. a stress radiograph to evaluate correction of the varus deformity.
4. a sunrise view to determine the status of the patellofemoral joint.
CORRECT ANSWER: C
DISCUSSION:
A patient with medial compartment arthritis and a correctable varus deformity with no clinical or examination findings of knee instability most likely has an intact anterior cruciate ligament (ACL). The pattern of medial compartment osteoarthritis most commonly associated with an intact ACL is that of anteromedial osteoarthritis. An incompetent ACL is commonly associated with a fixed varus deformity and radiographic signs of posteromedial wear. An incompetent ACL is a relative contraindication to a mobile-bearing UKA. When evaluating patients for a mobile-bearing UKA, a stress radiograph aids the orthopaedic surgeon in determining the correction of the varus deformity and assessing the lateral compartment. An inability to fully correct the deformity or narrowing of the lateral compartment with valgus stress should influence the surgeon against UKA. Joint registries across the world have shown decreased survivorship associated with TKA and UKA in men compared with other age groups, but survivorship is lower for UKA than for TKA. No studies to date have shown any differences in survivorship between fixed-bearing and mobile-bearing UKAs. The complication that is unique to mobile-bearing UKA is bearing spinout, which occurs in less than 1% of mobile-bearing UKA procedures. In vivo and in vitro polyethylene wear in mobile-bearing UKA are low. Arthritis may progress faster in patients with mobile-bearing UKAs than in those with fixed-bearing UKAs.
**Question 80** Compared with retention of the native patella in primary total knee arthroplasty, routine patellar resurfacing is associated with
1. no patellar complications.
2. an increased occurrence of anterior knee pain.
3. a reduced patellar fracture rate.
4. a reduced risk for revision surgery.
CORRECT ANSWER: D
DISCUSSION:
Despite concerns regarding fracture, osteonecrosis, and patellar clunk, the routine retention of the native patella during primary total knee replacement is associated with a 20% to 30% increased revision risk in
large joint registries. In addition, the retention of the native patella results in a 5.7% revision surgery rate in patients with anterior knee pain.
**Question 81** A surgeon prepares a medial gastrocnemius rotational flap to cover a medial proximal tibia defect at the time of revision knee replacement surgery. To optimize coverage, the surgeon must optimally mobilize which artery?
1. Profunda femoris
2. Middle genicular
3. Medial sural
4. Inferior medial genicular
CORRECT ANSWER: C
DISCUSSION:
The medial sural arteries vascularize the gastrocnemius, plantaris, and soleus muscles proximally. These arteries arise from the popliteal artery. If this artery is not adequately mobilized, a gastrocnemius soleus flap can be devascularized.
**Question 82** Figures below represent the radiographs obtained from a 37-year-old man with severe right knee pain. He has a history of prior tibial osteotomy for adolescent tibia vara but notes residual bowing of his legs. On examination, he is 5'8" tall and weighs 322 pounds. He has a waddling gait with a bilateral varus thrust and 20° varus deformity of both legs. His right knee range of motion is 0° to 120° with a fixed varus deformity. What is the best next step?

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1. Total knee arthroplasty with standard components
2. Correction of tibial deformity with osteotomy and nonsurgical management of the osteoarthritis
3. Arthrodesis with a long antegrade nail
4. Total knee arthroplasty with a constrained device
CORRECT ANSWER: D
DISCUSSION:
This patient has severe, uncorrectable varus deformity and pain from end-stage osteoarthritis secondary to prior adolescent tibia vara. Although he is young to consider arthroplasty, this option is likely to give him the most functional limb, compared with arthrodesis with a long antegrade nail. During arthroplasty surgery, his knee will likely require extensive medial release to achieve anatomic limb alignment. Standard components in total knee arthroplasty likely would result in lateral instability, so this option is
not the best answer. The best choice is total knee arthroplasty with a constrained device, which adds constraint to the knee to provide balance.
**Question 83** An 85-year-old obese woman has left knee pain. She had surgery 5 years ago for a patellar nonunion after total knee arthroplasty that was complicated by infection, which was treated with implant removal and patellectomy. She has not been ambulatory since then. She states she is no longer on antibiotics. She has moderate pain, but her primary problem is instability of the knee. She has a 40° extensor lag. Darkening of the skin is present distal to the incision consistent with venous stasis changes. The erythrocyte sedimentation rate is 12 mm/h (reference range 0 to 20 mm/h) and her C-reactive protein level is 1.0 mg/L (reference range 0.08 to 3.1 mg/L). Left knee aspiration shows a white blood cell count of 800 and 20% neutrophils. What is the best next step?
1. Revision total knee arthroplasty with primary quadriceps tendon repair
2. Hinged knee arthroplasty with full extensor mechanism allograft
3. Arthrotomy with debridement and antegrade knee arthrodesis nailing
4. Two-stage revision knee arthroplasty and quadriceps repair with Achilles allograft
CORRECT ANSWER: C
DISCUSSION:
This patient is elderly, obese, and nonambulatory and has a chronic quadriceps tendon rupture after infected total knee arthroplasty. Her potential for ambulation after revision total knee arthroplasty is very low. Primary repair of the tendon is unlikely to be successful, even with augmentation, so revision total knee arthroplasty with primary quadriceps tendon repair and two-stage revision knee arthroplasty and quadricep repair with Achilles allograft are not the best management techniques. Extensor mechanism allograft could be done but would have a high failure rate in a patient of this size. No sign of infection is seen, based on laboratory studies, so a two-stage procedure is not necessary. The best management although not optimal, would be treatment in a drop-lock brace. Arthrodesis is also an option, but would have a high complication rate, and in a patient that is nonambulatory, a fused knee would be increasingly difficult with activities of daily living and mobility.
**Question 84** Figures below depict the radiographs obtained from a 53-year-old man who has had swelling in his right knee for 2 years, with minimal pain. He did not note an injury to the knee but has been unable to ambulate without crutches during this period. His past history is unremarkable, and he denies a history of diabetes or back problems. The social history reveals that he emigrated from China, and he works at a desk job. Physical examination shows a healthy man in no acute distress. Range of motion of the right knee is 5° to 120° actively and 0° to 120° passively, without pain. Sensation is decreased on the bottom of both feet, but otherwise the neurologic examination is unremarkable. Laboratory testing reveals a positive rapid plasma reagin (RPR) test. What is the best next step?

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1. Open reduction and internal fixation
2. Hinged total knee arthroplasty
3. Arthrodesis using an intramedullary nail
4. Irrigation and debridement with spacer placement
CORRECT ANSWER: B
DISCUSSION:
This patient has a neuropathic knee caused by neurosyphilis, as shown by the joint destruction on the radiographs, with a lack of pain and a positive RPR test. He has a low-demand job and would be best treated with a hinged knee arthroplasty to provide stability for his knee.
**Question 85** At the time of revision knee arthroplasty, a surgeon performs a rectus snip to gain exposure to the knee. When compared with a standard parapatellar approach, what is the expected outcome?
1. Improvement in range of motion
2. Reduction in range of motion
3. Increase in extensor mechanism lag
4. No differences in motion and strength
CORRECT ANSWER: D
DISCUSSION:
Rectus snip during total knee arthroplasty has no effect on motion or strength at long-term follow-up. It has not been associated with extensor mechanism lag.
**Question 86** Hip pain of 1-month duration has developed in a 72-year-old man with a previous total hip arthroplasty. He underwent dental work 6 weeks ago. Aspiration shows a white blood cell count of more than 6,000 cells/μL (reference range 4,500 to 11,000 cells/μL) and the presence of gram-positive cocci in clusters on Gram stain. The orthopaedic surgeon recommends urgent debridement and irrigation. Fixation of the components is judged to be stable, and the surgeon elects to retain the implants. The patient has a final culture that reveals methicillin-resistant _Staphylococcus aureus_(MRSA). If the attending physician recommends the two-stage protocol, including the use of an antibiotic-cement spacer, what is the most likely prognosis for this patient?
1. Better functional outcome than that associated with infections from sensitive organisms
2. Same functional outcome as that associated with infections from sensitive organisms
1. Same prognosis for eradication of infection as that associated with infections from sensitive organisms
2. Poorer prognosis for eradication of infection than that associated with infection from sensitive organisms
CORRECT ANSWER: D
DISCUSSION:
The patient has a late infection of at least 4 weeks symptomatic duration that most likely is hematogenous in etiology. This infection is not an acute hematogenous infection that can successfully be treated with irrigation and debridement. Retention of the implants with debridement and irrigation alone has been associated with a poor prognosis. In a recent study, the success rate was only 44% in a series of 104 patients at a mean 5.7-year follow-up. In one study of 50 infections attributable to MRSA or methicillin-resistant _Staphylococcus epidermidis_ organisms treated with a two-stage protocol, the failure rate was 21%. Patients who experienced successful infection treatment had lower functional outcome measures using the Western Ontario and McMaster Universities Osteoarthritis Index, the University of California Los Angeles Activity Score, and the 12-item Oxford Knee Score, however.
**Question 87** An 80-year-old African American woman who lives in a large city is scheduled for total hip arthroplasty to address primary osteoarthritis. Part of the presurgical protocol includes nasal swab screening to assess for methicillin-resistant _Staphylococcus aureus_(MRSA) colonization. Which demographic factor places this patient at highest risk for a positive result?
1. Gender
2. Age
3. Race
4. Environment
CORRECT ANSWER: C
DISCUSSION:
Demographic factors are associated with increased risk for MRSA colonization, so it is important to identify vulnerable patients. Female gender and advanced age reduce the risk for colonization, whereas African American race increases this risk. Urban environments do not influence MRSA colonization.
**Question 88** Hip pain of 1-month duration has developed in a 72-year-old man with a previous total hip arthroplasty. He underwent dental work 6 weeks ago. Aspiration shows a white blood cell count of more than 6,000 cells/μL (reference range 4,500 to 11,000 cells/μL) and the presence of gram-positive cocci in clusters on Gram stain. The orthopaedic surgeon recommends urgent debridement and irrigation. Fixation of the components is judged to be stable, and the surgeon elects to retain the implants. What is this patient's prognosis for infection resolution?
1. Good because it is a gram-positive organism
2. Good because it is an acute infection
3. Poor because it is a gram-positive organism
4. Poor because it is a late infection
CORRECT ANSWER: D
DISCUSSION:
The patient has a late infection of at least 4 weeks symptomatic duration that most likely is hematogenous in etiology. This infection is not an acute hematogenous infection that can successfully be treated with irrigation and debridement. Retention of the implants with debridement and irrigation alone has been associated with a poor prognosis. In a recent study, the success rate was only 44% in a series of 104 patients at a mean 5.7-year follow-up. In one study of 50 infections attributable to MRSA or methicillin-resistant _Staphylococcus epidermidis_ organisms treated with a two-stage protocol, the failure rate was 21%. Patients who experienced successful infection treatment had lower functional outcome measures using the Western Ontario and McMaster Universities Osteoarthritis Index, the University of California Los Angeles Activity Score, and the 12-item Oxford Knee Score, however.
**Question 89** A 40-year-old man with a history of Legg-Calve-Perthes disease underwent a right hip resurfacing 3 years ago with no perioperative complications. Hip pain has developed gradually during the last 4 months. Radiographs show no evidence of fixation loosening or any adverse changes at the femoral neck. No periarticular osteolysis is evident. What is the most appropriate management of this condition?
1. Continue to observe with repeat radiographs in 6 months
2. Fluoroscopic-guided iliopsoas tendon cortisone injection
3. Hip aspiration
4. Serum cobalt and chromium levels and metal-reduction MRI scan
CORRECT ANSWER: D
DISCUSSION:
Controversy persists over what exactly is the best approach to managing patients with metal-on-metal (MOM) hip arthroplasties. All patients with painful MOM hip arthroplasties should be examined for fixation loosening, wear/osteolysis, and infection—no differently than patients without MOM hip arthroplasties. It is recommended to obtain serum trace element levels. If the levels are high, cross-sectional imaging should be obtained to determine whether any pseudotumor or tissue necrosis is present around the hip arthroplasty. Hip aspiration should be considered if concern for infection exists. Adverse tissue reaction has been identified to occur around MOM hip arthroplasties. The predominant histologic feature is tissue necrosis with infiltration of lymphocytes and plasma cells.
**Question 90** In patients undergoing elective hip or knee arthroplasty who are not at elevated risk (beyond the risk associated with the surgery) for venous thromboembolism or bleeding, using pharmacologic agents and/or mechanical compressive devices for the prevention of venous thromboembolism was assigned what grade of recommendation by the 2011 AAOS Clinical Practice Guideline, Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty?
1. Strong
2. Moderate
3. Limited
4. Inconclusive
CORRECT ANSWER: B
DISCUSSION:
Using pharmacologic agents and/or mechanical compressive devices for the prevention of venous thromboembolism in patients undergoing elective hip or knee arthroplasty who are not at elevated risk beyond that of the surgery itself for venous thromboembolism or bleeding was given a moderate grade of recommendation in the 2011 AAOS Clinical Practice Guideline referenced above.
**Question 91** A 40-year-old man with a history of Legg-Calve-Perthes disease underwent a right hip resurfacing 3 years ago with no perioperative complications. Hip pain has developed gradually during the last 4 months. Radiographs show no evidence of fixation loosening or any adverse changes at the femoral neck. No periarticular osteolysis is evident. A large intra-articular and intrapelvic pseudotumor has developed. What predominant histological feature(s) is/are present in such a lesion?
1. Polymorphonuclear leukocytes
2. Extracellular metal-wear debris
3. Cement particles within the macrophages
4. Lymphocytes and plasma cells
CORRECT ANSWER: D
DISCUSSION:
Controversy persists over what exactly is the best approach to managing patients with metal-on-metal (MOM) hip arthroplasties. All patients with painful MOM hip arthroplasties should be examined for fixation loosening, wear/osteolysis, and infection—no differently than patients without MOM hip arthroplasties. It is recommended to obtain serum trace element levels. If the levels are high, cross-sectional imaging should be obtained to determine whether any pseudotumor or tissue necrosis is present around the hip arthroplasty. Hip aspiration should be considered if concern for infection exists. Adverse tissue reaction has been identified to occur around MOM hip arthroplasties. The predominant histologic feature is tissue necrosis with infiltration of lymphocytes and plasma cells.
**Question 92** A 57-year-old woman experiences pain 1 year after total knee arthroplasty (TKA). She reports sharp anterior pain and a painful catching sensation that is aggravated by rising from a chair or climbing stairs. Physical examination reveals a mild effusion and a range of motion of 2° to 130°, with patellar crepitus. The symptoms are reproduced by resisted knee extension. Radiographs show a well-aligned posterior-stabilized TKA without evidence of component loosening. What is the recommended treatment for this patient?
1. Physical therapy
2. Arthroscopic synovectomy
3. Tibial insert revision
4. Femoral component revision
CORRECT ANSWER: B
DISCUSSION:
Patellar clunk syndrome is caused by the development of a fibrous nodule on the posterior aspect of the quadriceps tendon at its insertion into the patella. It causes a painful catching sensation when the extensor
mechanism traverses over the trochlear notch as the knee extends from 45° of flexion to 30° from full extension. It characteristically occurs in posterior stabilized total knee arthroplasties and appears to be related to femoral component design. The syndrome can usually be prevented by excising the residual synovial fold just proximal to the patella. Flexion gap instability can also cause a painful total knee arthroplasty but is less common in posterior stabilized implants. Femoral component malrotation can cause pain attributable to a flexion gap imbalance or patellar tracking problems. Polyethylene wear would be unlikely after just 1 year. Patellar clunk syndrome can usually be addressed successfully with arthroscopic synovectomy. Recurrence is uncommon. Physical therapy may help to strengthen the quadriceps following synovectomy but would not resolve the clunk syndrome symptoms. Femoral or tibial insert revision is not indicated if patellar clunk syndrome is the only problem resulting in a painful total knee arthroplasty.
**Question 93**
Which modality has the broadest application for the reduction of postsurgical transfusion?
1. Regional anesthesia
2. Tranexamic acid (TXA) administration
3. Reduced transfusion trigger
4. Hypotensive anesthesia
CORRECT ANSWER: B
DISCUSSION:
TXA is easy to administer, inexpensive, and safe for virtually all patients. Multiple studies have demonstrated transfusion rates lower than 3% for total knee arthroplasty and lower than 10% for total hip arthroplasty. Regional and hypotensive anesthesia effectively reduce transfusion; however, they cannot be used in as wide a range of patients as can TXA. A reduced transfusion trigger must be considered along with patient symptoms when determining the need for transfusion.
**Question 94**
When do most symptomatic thromboembolic events occur after total joint arthroplasty?
D. More than 3 months after surgery
1. On the day of surgery
2. Within the first week after surgery
3. Between 1 week and 6 weeks after surgery
CORRECT ANSWER: C
DISCUSSION:
Most clinical venous thromboembolism events occur between the second and sixth weeks after surgery. It is estimated that 10% of patients are readmitted to the hospital within the first 3 months after total hip or knee arthroplasties. Most pulmonary events on the day of surgery are related to fat embolism or cardiac events.
**Question 95** When comparing arthroscopic lavage and knee debridement with placebo in patients with chronic symptomatic osteoarthritis, what outcome has been demonstrated?
1. Reliable and durable pain relief
2. No significant benefit for chronic osteoarthritis
3. Up to 75% pain relief for 2 months, then variable response
4. Three-month measurable pain relief, followed by recurrence
CORRECT ANSWER: B
DISCUSSION:
Excluding a diagnosis of meniscal tear, loose body, or mechanical derangement, treating knee osteoarthritis of indeterminate cause with arthroscopic lavage and debridement has been found to provide no discernable benefit to offset the risk of surgery. The effects of arthroscopy have not been clinically significant in the vast majority of patient-oriented outcomes measures for pain and function at multiple times between 1 week and 2 years after surgery.
**Question 96** Figure below shows the abdominal radiograph obtained from a 70-year-old woman who experiences nausea and abdominal tightness 48 hours following left total knee arthroplasty performed under general anesthesia. She received 24 hours of cefazolin antibiotic prophylaxis and a patient-controlled analgesia narcotic pump for pain management. She has been receiving warfarin for thromboembolic prophylaxis. Her severe abdominal distension and markedly decreased bowel sounds are most likely secondary to the administration of

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1. general anesthesia.
2. antibiotics.
3. warfarin.
4. narcotics.
CORRECT ANSWER: D
DISCUSSION:
The radiograph reveals severe intestinal dilatation, which has occurred as the result of acute colonic pseudo-obstruction and is associated with excessive narcotic administration following total joint arthroplasty. Anesthetic type, antibiotic administration, and warfarin have not been associated with this obstruction. Electrolyte imbalances such as hypokalemia have been associated with postsurgical acute colonic pseudo-obstruction.
**Question 97** Venous thromboembolism may occur after total joint arthroplasty. The risk of this complication is elevated in patients with
1. a BMI lower than 30.
2. diabetes mellitus, with a hemoglobin A1c test result less than 7.
3. tranexamic acid use.
4. metabolic syndrome.
CORRECT ANSWER: D
DISCUSSION:
Obesity, a prior history of venous thromboembolism, and metabolic syndrome have all been associated with an increased risk of thromboembolism. A recent meta-analysis showed that diabetes had no significant relationship with venous thromboembolism following hip or knee arthroplasty. Tranexamic acid is an antifibrinolytic agent that has been shown to reduce blood loss substantially following hip and knee arthroplasty. It has also been shown to be safe in patients with severe medial comorbidities and a prior history of venous thromboembolism.
**Question 98** A 70-year old woman undergoes revision total knee arthroplasty for tibial component aseptic loosening. She is concerned about recurrent loosening, and tibial stem fixation options during revision are reviewed. Figure below displays a radiograph of the revision technique used for this patient. What is the incidence of intraoperative tibial shaft fracture that is associated with this type of revision surgery?

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1. 0% to 1% with press-fit tibial stems
2. 3% to 5% with press-fit tibial stems
3. 3% to 5% with cemented tibial stems
4. More than 5% with press-fit tibial stems
CORRECT ANSWER: B
DISCUSSION:
Using press-fit tibial stems during a hybrid revision total knee arthroplasty is associated with a 3% to 5% incidence of intraoperative tibial shaft fracture. Diaphyseal fixation of press-fit stems has the advantage of setting component alignment, dispersing forces on the proximal tibia, and offers excellent clinical results. The disadvantages include proximal and distal tibia anatomic mismatch and tibial shaft fracture. Cipriano and associates reported a tibial shaft fracture incidence of 4.9% in a series of 420 consecutive
knee revisions. All fractures healed with nonsurgical management, and none led to implant loosening. In this patient, it is important to recognize on the radiograph that this technique is a hybrid method of revision total knee arthroplasty, with cementation along the tibial tray and metaphysis and with press-fit fixation of the diaphyseal engaging stem. Then, it is important to know the risk and management of intraoperative diaphyseal tibial fractures. Cemented tibial stems are associated with a low rate of intraoperative fracture, because the implant is typically undersized to allow for an appropriate cement mantle. Option C is incorrect, because this revision is not cemented. Option A underestimates the incidence of fracture, whereas D overestimates the rate of fracture.
**Question 99** Figures below depict the radiographs obtained from a 60-year-old man with instability and pain 1 year after primary right total knee arthroplasty. He states that he had surgery on two occasions for a tendon rupture that was repaired with sutures but that his knee popped again, and now the leg is unable to hold his weight. On examination, he is in no acute distress. His height is 6'3", and he weighs 240 pounds. He is ambulatory with crutches. Range of motion of the right knee is 50° to 120° actively and 0° to 120° passively. More than 10° of varus/valgus laxity and more than 5 mm of anteroposterior drawer are present. A palpable defect is observed in the tissue just proximal to the patella. The incision is well healed. The erythrocyte sedimentation rate is 46 mm/h (reference range 0 to 20 mm/h) and the C-reactive protein level is 2.04 mg/L (reference range 0.08 to 3.1 mg/L). Aspiration of the right knee reveals hazy yellow fluid with a white blood cell count of 120 and 1% neutrophils. No growth of organisms is seen on routine culture. What is the best next step?

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1. Revision total knee arthroplasty with extensor mechanism allograft
2. Revision total knee arthroplasty with liner change and primary quadriceps repair
3. Resection knee arthroplasty and arthrodesis with antegrade nail
4. Two-stage revision total knee arthroplasty with extensor mechanism allograft
CORRECT ANSWER: A
DISCUSSION:
This patient has a chronic quadriceps tendon rupture after total knee arthroplasty. Two previous primary repair attempts have failed, which is not surprising based on the poor results of primary repair reported in the literature. The patient also has an unstable knee and will require revision of some or all of the prosthesis to achieve a stable knee. Revision total knee arthroplasty with extensor mechanism allograft allows an allograft reconstruction of the ruptured quadriceps tendon. The other option is to utilize a synthetic mesh extensor mechanism reconstruction. These are likely to have the best result in this situation. Revision total knee arthroplasty with liner change and primary quadriceps repair is not the best form of management, because it involves a third attempt at primary tendon repair, which will likely fail again. Resection knee arthroplasty and arthrodesis with antegrade nail is a possible option but is not the best, because it would likely make driving and other daily activities difficult. Two-stage revision total
knee arthroplasty with extensor mechanism allograft is not the best option because the laboratory results show no signs of infection, so a single-stage procedure is preferred.
**Question 100** A 60-year-old man who underwent left partial knee arthroplasty 6 months earlier was doing well until he experienced left knee pain and swelling for 4 weeks following a dental procedure. The left knee aspirate was bloody, with a white blood cell count of 8,000 and 70% neutrophils. Culture grew group B Streptococcus (_Granulicatella adiacens_), and serologies were elevated, with an erythrocyte sedimentation rate of 55 mm/h (reference range: 0 to 20 mm/h) and a C-reactive protein level of 24 mg/L (reference range: 0.08 to 3.1 mg/L). What is the best next step?
1. Arthroscopic debridement
2. Two-stage total knee revision arthroplasty
3. Resection arthroplasty without an antibiotic impregnated cement spacer
4. Knee fusion
CORRECT ANSWER: B
DISCUSSION:
This complication is best addressed with either a single-stage or two-stage total knee arthroplasty. A recent report suggests that a single-stage arthroplasty can be effective, although many surgeons would perform a two-stage procedure with an articulating or static spacer. Arthroscopic would be non-effective, especially given 4 weeks of symptoms. Resection arthroplasty without a spacer would leave an unstable _and poorly functioning extremity. Knee fusion should be used as a salvage procedure._