Orthopedic Board Review MCQs: Hip & Knee Arthroplasty

Question 1

A 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?

Explanation

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 2

A 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 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?

Explanation

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 3

A 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 below. What is the best option for the restoration of her function?

Explanation

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 4

below show the radiographs, and the CT obtained from a 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?

Explanation

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 5

A year-old woman is scheduled to undergo right total hip arthroplasty. Her preoperative radiograph is shown in below. To avoid increasing this patient’s combined offset while maintaining her leg length, what is the most appropriate surgical plan?

Explanation

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 6

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?

Explanation

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 7

A 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?

Explanation

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 8

What is the most important preoperative factor predicting conversion to total hip arthroplasty after arthroscopic surgery of the hip?

Explanation

DISCUSSION:
The authors cited in the 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

Question 9

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?

Explanation

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 10

below depict the radiographs obtained from a 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?

Explanation

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 11

below show the clinical photograph and radiograph obtained from a year-old man who has deformity and pain 1 year after primary total hip arthroplasty. What is the reason for the observed deformity?

Explanation

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 12

below show the radiographs obtained from an 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?

Explanation

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 13

below shows the radiograph obtained from a 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?

Explanation

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 14

A 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?

Explanation

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 15

Injury to the popliteal artery during total knee arthroplasty (TKA) is most likely to occur when placing a sharp retractor

Explanation

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 16

A year-old woman has a 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 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

Explanation

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 17

A year-old woman has a 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 degree mechanical axis deformity. The deformity shown in below is predominantly associated with

Explanation

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 18

below show the radiographs, and the MRIs obtained from a year-old man with worsening left knee pain. A foot hip-to-ankle radiograph shows a 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?

Explanation

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 19

When balancing gaps in the coronal plane, what structure preferentially impacts the flexion space more than the extension space?

Explanation

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 20

A 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?

Explanation

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 21

below show the radiographs obtained from a 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?

Explanation

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 22

A 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?

Explanation

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 23

A 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?

Explanation

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 24

A 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?

Explanation

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 25

A year-old man with a body mass index of 31 had a 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

Explanation

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 26

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?

Explanation

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 27

What factor is considered one of the early changes in osteoarthritic cartilage?

Explanation

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 28

A 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?

Explanation

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 29

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?

Explanation

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 30

A 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?

Explanation

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 31

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?

Explanation

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 32

A 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?

Explanation

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 33

During a posterior cruciate ligament (PCL)-retaining total knee arthroplasty, a critical principle to remember is to

Explanation

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 34

below depict the AP and lateral radiographs obtained from a 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?

Explanation

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 35

below shows the standing AP radiograph obtained from a year-old man who has a 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

Explanation

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 36

Compared with retention of the native patella in primary total knee arthroplasty, routine patellar resurfacing is associated with

Explanation

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 37

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?

Explanation

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 38

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?

Explanation

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 39

An 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 0 mg/L (reference range 08 to 1 mg/L). Left knee aspiration shows a white blood cell count of 800 and 20% neutrophils. What is the best next step?

Explanation

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 40

below depict the radiographs obtained from a 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 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?

Explanation

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 41

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?

Explanation

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 42

Hip pain of month duration has developed in a 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?

Explanation

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 43

An 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?

Explanation

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 44

Hip pain of month duration has developed in a 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?

Explanation

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 45

A 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?

Explanation

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 46

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?

Explanation

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 47

A 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?

Explanation

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 48

A 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?

Explanation

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 49

Which modality has the broadest application for the reduction of postsurgical transfusion?

Explanation

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 50

When do most symptomatic thromboembolic events occur after total joint arthroplasty?

Explanation

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 51

A 68-year-old woman is scheduled for a primary total hip arthroplasty (THA). Preoperative spinopelvic assessment reveals a rigid, flatback deformity with a loss of lumbar lordosis. The pelvis is locked in severe posterior pelvic tilt. To minimize her risk of postoperative dislocation, how should the target acetabular component orientation be adjusted?

Explanation

A rigid flatback deformity causes fixed posterior pelvic tilt, which functionally increases acetabular anteversion and predisposes the patient to anterior dislocation in extension. The surgeon must decrease the cup anteversion to compensate for the pelvic position.

Question 52

A 72-year-old man presents with a painful total knee arthroplasty 3 years after the index surgery. Serum erythrocyte sedimentation rate and C-reactive protein are elevated. Synovial aspiration yields a white blood cell count of 2,500 cells/mcL with 65% polymorphonuclear leukocytes. Which of the following synovial fluid biomarkers has the highest specificity for diagnosing a periprosthetic joint infection (PJI)?

Explanation

Alpha-defensin is a biomarker released by neutrophils in response to pathogens. It has a high sensitivity and the highest specificity (near 96-100%) for diagnosing periprosthetic joint infections compared to traditional inflammatory markers.

Question 53

A 58-year-old man presents with progressive groin pain 6 years after a primary metal-on-polyethylene total hip arthroplasty utilizing a titanium stem and a cobalt-chromium modular head. Radiographs are unremarkable, but MRI with metal artifact reduction sequence (MARS) demonstrates a cystic fluid collection around the hip. Serum cobalt levels are significantly elevated. What is the most likely diagnosis?

Explanation

Trunnionosis, or mechanically assisted crevice corrosion, occurs at the modular head-neck junction. It can happen in metal-on-polyethylene bearings with CoCr heads, leading to elevated serum cobalt, adverse local tissue reactions (ALTR), and cystic masses.

Question 54

A 71-year-old woman presents to the emergency department after a fall. She underwent a cementless total hip arthroplasty 10 years ago. Radiographs reveal a periprosthetic fracture around the femoral stem. The fracture line extends just distal to the tip of the stem, the stem is grossly loose, but there is adequate proximal and distal bone stock. According to the Vancouver classification, what is the most appropriate surgical treatment?

Explanation

This is a Vancouver B2 fracture (fracture around or just below the stem, loose stem, adequate bone stock). The gold standard treatment is revision to a longer, diaphyseal-engaging stem, most commonly a fluted, tapered, modular cementless stem.

Question 55

During a primary total knee arthroplasty, the surgeon uses a measured resection technique. After making the initial bony cuts, the trial components are placed. The knee is found to be tight in full extension, but the medial and lateral gaps are symmetric and well-balanced in 90 degrees of flexion. What is the most appropriate next step to balance the knee?

Explanation

A tight extension gap with a well-balanced flexion gap requires resection of more distal femur. Distal femoral resection affects only the extension gap without altering the flexion space.

Question 56

A 65-year-old man with a well-functioning right total hip arthroplasty placed 4 years ago presents with 2 days of severe right hip pain, fevers, and chills. He recently recovered from bacterial pneumonia. Aspiration of the hip yields purulent fluid with 85,000 WBCs/mcL. Radiographs show well-fixed components without radiolucencies. What is the most appropriate definitive surgical management?

Explanation

This is an acute hematogenous periprosthetic joint infection (symptoms < 3 weeks in a previously well-functioning, well-fixed joint). DAIR with exchange of modular components is indicated for acute hematogenous PJI to clear the infection while retaining the well-fixed implants.

Question 57

A 55-year-old woman with severe bilateral developmental dysplasia of the hip (Crowe Type IV) is scheduled for a total hip arthroplasty. Which of the following anatomic abnormalities is expected on the femoral side when compared to a non-dysplastic hip?

Explanation

Patients with severe hip dysplasia (Crowe IV) typically exhibit a narrow, "stove-pipe" or extremely narrow medullary canal, excessive femoral anteversion, and an anteriorly displaced greater trochanter with a valgus neck-shaft angle.

Question 58

A 64-year-old man presents 18 months after a posterior-stabilized total knee arthroplasty with complaints of an audible and palpable "clunk" when transitioning from a sitting to a standing position. Examination reveals a catch at approximately 35 degrees of knee flexion during active extension. What is the primary etiology of this phenomenon?

Explanation

Patellar clunk syndrome occurs in posterior-stabilized TKA when a fibrosynovial nodule forms at the superior pole of the patella. As the knee extends from flexion (usually around 30-45 degrees), the nodule pops out of the femoral intercondylar box, causing a painful clunk.

Question 59

A surgeon is evaluating a 65-year-old man for a THA. Standing and sitting lateral spinopelvic radiographs are obtained. From the standing to the sitting position, the pelvic incidence minus lumbar lordosis (PI-LL) mismatch increases by 15 degrees, and the sacral slope decreases by 15 degrees. How would you categorize this patient's spinopelvic mobility?

Explanation

Normal spinopelvic mobility involves a decrease in sacral slope of 10 to 30 degrees when transitioning from standing to sitting, accommodating hip flexion by posterior pelvic tilt and reduction of lumbar lordosis.

Question 60

During a primary total knee arthroplasty for a severe valgus deformity (>20 degrees), the surgeon sequentially releases lateral structures. After releasing the iliotibial band and the popliteus tendon off the femur, the lateral compartment remains tight in extension. What is the next most appropriate structure to release?

Explanation

The standard sequence for lateral release in a valgus knee typically begins with osteophytes, followed by the IT band (if tight in extension) and popliteus (if tight in flexion). The lateral collateral ligament is the next major structure released to balance a fixed valgus deformity.

Question 61

A 68-year-old woman underwent a ceramic-on-ceramic total hip arthroplasty 2 years ago. She now complains of a squeaking noise coming from the hip during walking, though she denies significant pain. Radiographs show a well-fixed stem and a cup with 55 degrees of inclination and 30 degrees of anteversion. What is the most likely biomechanical cause of the squeaking?

Explanation

Squeaking in ceramic-on-ceramic THA is heavily correlated with edge loading, which typically occurs due to component malposition, microseparation, or impingement. The cup inclination of 55 degrees (excessive) in this vignette strongly predisposes to edge loading.

Question 62

In the recovery room following a complex total knee arthroplasty for a 25-degree fixed valgus deformity, the patient is noted to have a dense foot drop and numbness in the first web space. Pedal pulses are bounding. What is the most appropriate immediate intervention?

Explanation

Peroneal nerve palsy is a known complication of correcting a severe valgus deformity. The immediate management is to remove all compressive dressings and place the knee in slight flexion to relieve tension on the nerve.

Question 63

A 74-year-old woman is evaluated for a medial unicompartmental knee arthroplasty (UKA). Which of the following preoperative clinical findings is considered an absolute contraindication to a medial UKA?

Explanation

An intact anterior cruciate ligament is a classic prerequisite for unicompartmental knee arthroplasty. ACL deficiency leads to altered kinematics, increased shear forces, and a higher risk of early failure due to component loosening or polyethylene wear.

Question 64

A 78-year-old woman with osteoporosis is undergoing primary total hip arthroplasty. Preoperative templating demonstrates a Dorr Type C proximal femur, characterized by a wide medullary canal with thin cortices and loss of the medial calcar. Which of the following femoral component types is most appropriate to ensure long-term survivorship in this specific bone morphology?

Explanation

Dorr Type C bone has a capacious, "stove-pipe" canal with thin cortices, making rigid initial fixation with cementless stems difficult and increasing the risk of subsidence or periprosthetic fracture. A cemented stem is highly recommended in this morphology.

Question 65

A 60-year-old man presents with an inability to actively extend his knee 3 months after a primary total knee arthroplasty. Ultrasound confirms a massive, chronic disruption of the quadriceps tendon with significant tissue retraction. He has failed nonoperative management with a brace. What is the most reliable surgical reconstruction method for this chronic defect?

Explanation

For chronic or massive extensor mechanism disruptions following TKA, primary repair universally fails. Synthetic (Marlex) mesh reconstruction has shown superior clinical results and survivorship compared to allograft tissues for bridging large extensor mechanism defects.

Question 66

A 71-year-old woman is undergoing a two-stage exchange arthroplasty for a chronic periprosthetic joint infection of her knee. Six weeks after removal of components, debridement, and placement of an articulating antibiotic spacer, she completes her IV antibiotic course. Two weeks off antibiotics, her knee is warm, erythematous, and a synovial aspirate reveals 60,000 WBC/mcL. What is the most appropriate next step in management?

Explanation

The patient has failed the initial first-stage debridement as evidenced by persistent clinical and laboratory signs of infection. The correct protocol is to repeat the first-stage procedure (I&D, spacer exchange) before considering reimplantation or salvage procedures.

Question 67

During a posterior approach to the hip for total hip arthroplasty, a sequence of short external rotators is identified and tagged for later repair. Which muscle in this region should be carefully preserved or partially released to protect the underlying sciatic nerve from direct surgical trauma?

Explanation

The quadratus femoris is located inferior to the obturator externus and directly overlies the sciatic nerve as it descends. Leaving the deep fascia or muscle belly of the quadratus femoris intact (or releasing only its most superior portion) protects the sciatic nerve during capsular exposure.

Question 68

A 65-year-old asymptomatic woman returns for a 3-year follow-up after a primary total hip arthroplasty using a fully porous-coated cementless femoral stem. Radiographs demonstrate focal loss of cortical bone density and radiolucencies specifically in Gruen zones 1 and 7, while the distal stem appears rigidly fixed. What is the most likely etiology of these radiographic findings?

Explanation

Fully porous-coated or extensively coated diaphyseal engaging stems often bypass proximal bone loading, resulting in stress shielding. This presents as proximal bone resorption and radiolucencies in Gruen zones 1 and 7 (the proximal femur) while the stem remains completely stable.

Question 69

A 60-year-old man with severe hemophilia A is scheduled for a bilateral total knee arthroplasty. To prevent catastrophic bleeding and hematoma formation, what target level of Factor VIII must be maintained intraoperatively?

Explanation

In patients with severe hemophilia A undergoing major orthopedic surgery (like TKA), Factor VIII levels must be replaced to 100% of normal immediately prior to and during surgery. Levels are typically maintained above 50% for 1-2 weeks postoperatively.

Question 70

A 65-year-old man who underwent a primary total knee arthroplasty 4 weeks ago presents with a 3-day history of acute fever, severe knee pain, and swelling. Aspiration reveals synovial fluid with 65,000 WBCs/uL and 95% neutrophils. What is the most appropriate management?

Explanation

DAIR is indicated for acute postoperative periprosthetic joint infections (less than 4 weeks from surgery) or acute hematogenous infections with symptoms less than 3 weeks. Well-fixed components should be retained and the modular polyethylene liner exchanged to access the posterior joint for thorough debridement.

Question 71

A 70-year-old woman complains of recurrent knee swelling and a feeling of giving way when descending stairs, 2 years after a primary TKA. Range of motion is 0 to 120 degrees. Examination reveals a stable knee in full extension, but significant varus, valgus, and anteroposterior laxity at 90 degrees of flexion. What is the most likely cause of this instability?

Explanation

Flexion instability is characterized by a knee that is well-balanced in extension but loose in flexion. This most commonly results from an undersized femoral component in the anteroposterior dimension, excessive distal femoral resection, or failure to balance the flexion gap.

Question 72

A 62-year-old woman complains of groin pain 1 year after an uncomplicated THA. The pain is worst when getting out of a car and actively lifting her leg into bed. Resisted active hip flexion reproduces the pain. Radiographs show the acetabular component in 40 degrees of abduction and 20 degrees of anteversion, but the anterior rim protrudes 4 mm beyond the anterior acetabular wall. What is the most appropriate initial treatment?

Explanation

This patient's symptoms and radiographic findings are highly consistent with iliopsoas impingement secondary to a prominent anterior acetabular rim. Initial management should be conservative, consisting of rest, NSAIDs, and a corticosteroid injection, before considering surgical release or component revision.

Question 73

A 78-year-old man presents with thigh pain and inability to bear weight after a mechanical fall. He has an uncemented THA placed 12 years ago. Radiographs demonstrate a displaced fracture around the femoral stem. The stem has subsided by 2 cm, and there is severe proximal femoral osteolysis with complete loss of the calcar. What is the most appropriate treatment?

Explanation

This is a Vancouver B3 periprosthetic fracture, characterized by a loose stem and severe proximal bone loss. In an elderly patient, a proximal femoral replacement bypasses the bone loss, provides immediate stability, and allows for early weight-bearing.

Question 74

A 55-year-old man presents with increasing groin pain 6 years after a metal-on-polyethylene THA with a 36-mm cobalt-chromium femoral head on a titanium stem. Blood tests reveal an elevated serum cobalt level and a normal chromium level. MRI with metal artifact reduction sequence (MARS) reveals a cystic mass in the hip abductors. What is the most likely diagnosis?

Explanation

Elevated cobalt out of proportion to chromium in a metal-on-polyethylene THA indicates mechanically assisted crevice corrosion at the modular head-neck junction, known as trunnionosis. This corrosion can lead to an adverse local tissue reaction (ALTR) and pseudotumor formation.

Question 75

A 65-year-old woman reports anterior knee pain and frequent subluxation of her patella 1 year following a primary TKA. Clinical examination demonstrates severe patellar apprehension and lateral tracking. A CT scan to evaluate component position is most likely to show which of the following?

Explanation

Internal rotation of either the femoral or tibial components increases the Q-angle, leading to lateral patellar maltracking, subluxation, and anterior knee pain. Proper external rotation of the femoral component and lateralization of the patellar button help optimize patellar tracking.

Question 76

According to the Musculoskeletal Infection Society (MSIS) criteria, which of the following findings is considered a major criterion, confirming a definitive diagnosis of a periprosthetic joint infection?

Explanation

Under the MSIS criteria, definitive PJI is established by either a sinus tract communicating with the joint or two positive periprosthetic cultures with phenotypically identical organisms. The other choices are considered minor criteria.

Question 77

A 72-year-old woman sustained a patellar tendon rupture 5 years after her TKA. A primary repair failed, leaving her with an inability to actively extend the knee. She is undergoing reconstruction with a full extensor mechanism allograft. To maximize the chance of a successful outcome and prevent an extensor lag, how should the allograft be tensioned?

Explanation

When reconstructing the extensor mechanism with an allograft, it must be tensioned tightly in full extension. Failure to do so uniformly leads to a significant extensor lag due to subsequent graft stretch-out during rehabilitation.

Question 78

A 68-year-old woman is undergoing revision THA for severe aseptic loosening. Intraoperatively, the superior and inferior halves of the acetabulum are found to move independently. Which of the following is the most appropriate management strategy for the acetabulum?

Explanation

Independent movement of the superior and inferior hemipelvis indicates a pelvic discontinuity. Successful management requires rigid fixation spanning the defect, most reliably achieved with a cup-cage construct, custom triflange, or a distraction approach using porous tantalum.

Question 79

During a primary THA using the direct anterior (Smith-Petersen) approach, the surgeon develops the internervous plane between the sartorius and the tensor fasciae latae. Which of the following nerves is at greatest risk of injury during this superficial dissection?

Explanation

The lateral femoral cutaneous nerve (LFCN) crosses the anterior thigh and is at significant risk of injury during the superficial dissection of the direct anterior approach. The internervous plane is between the sartorius (femoral n.) and the tensor fasciae latae (superior gluteal n.).

Question 80

A 60-year-old man sustained a posterior dislocation of his primary THA 3 weeks postoperatively while bending over. Closed reduction was successful. Radiographs demonstrate the acetabular cup is positioned in 10 degrees of anteversion and 40 degrees of abduction. The femoral stem is in 5 degrees of retroversion. What is the primary cause of his dislocation?

Explanation

The patient has a combined anteversion of only 5 degrees (10 degrees cup + -5 degrees stem), which is significantly lower than the target safe zone of 25 to 35 degrees. This lack of combined anteversion strongly predisposes the hip to posterior dislocation.

Question 81

A 65-year-old man undergoes aspiration of a painful THA 2 years after surgery. The synovial fluid shows a WBC count of 45,000 cells/uL with 90% neutrophils. Aerobic and anaerobic cultures are negative at 5 days. Due to high suspicion, cultures are held longer, and at 12 days yield a gram-positive, anaerobic rod. What is the most likely pathogen?

Explanation

Cutibacterium (formerly Propionibacterium) acnes is a slow-growing, anaerobic, gram-positive rod. It often requires extended culture times (up to 14 days) to be identified and is a well-known cause of indolent periprosthetic joint infections.

Question 82

A 45-year-old man who underwent a ceramic-on-ceramic THA 3 years ago complains of a high-pitched squeaking noise coming from his hip when walking. He denies pain. Radiographs show a well-fixed cup in 60 degrees of abduction and a well-fixed stem. What is the most likely etiology of the squeaking?

Explanation

Squeaking in ceramic-on-ceramic hips is often associated with component malposition, particularly a vertically placed cup (abduction angle > 50 degrees). This verticality leads to edge loading, disruption of fluid-film lubrication, and subsequent noise generation.

Question 83

A 65-year-old man presents with chronic right knee pain 2 years after a primary TKA. ESR is 45 mm/hr and CRP is 2.5 mg/dL. Aspiration yields 4,500 WBCs/mcL with 85% neutrophils. Cultures are negative at 7 days. Which of the following synovial fluid biomarkers would be most specific to confirm a periprosthetic joint infection?

Explanation

Alpha-defensin is a highly specific and sensitive synovial biomarker for periprosthetic joint infection, especially in culture-negative cases. It is an antimicrobial peptide released by neutrophils in response to pathogens.

Question 84

A 72-year-old woman experiences her third posterior dislocation 4 months after a primary right THA performed via a posterior approach. Radiographs show the acetabular component is in 30 degrees of inclination and 5 degrees of retroversion. The femoral stem is stable and in 15 degrees of anteversion. What is the most appropriate surgical intervention?

Explanation

The acetabular component is retroverted (normal target is 15-20 degrees of anteversion). Revision of the malpositioned acetabular component is the definitive treatment for recurrent posterior instability due to cup retroversion.

Question 85

A 68-year-old woman complains of a painful catching sensation in her anterior knee when extending from a flexed position, 1 year after a posterior-stabilized TKA. On examination, a palpable "clunk" is felt at 35 degrees of flexion as the knee actively extends. Radiographs show well-fixed components with no evidence of loosening. What is the most likely diagnosis?

Explanation

Patellar clunk syndrome occurs in posterior-stabilized TKA designs when a fibrosynovial nodule forms at the superior pole of the patella and catches in the intercondylar notch. Treatment typically involves arthroscopic or open excision of the nodule.

Question 86

A 55-year-old man presents with right groin pain and a palpable anterior mass 6 years after a metal-on-polyethylene THA with a large-diameter cobalt-chrome femoral head. Laboratory studies show an ESR of 10 mm/hr, CRP of 0.4 mg/dL, and elevated serum cobalt levels with normal chromium. What is the most likely cause of his symptoms?

Explanation

Elevated serum cobalt levels with normal chromium in a metal-on-polyethylene bearing strongly suggest mechanically assisted crevice corrosion (trunnionosis) at the head-neck junction. This can lead to an adverse local tissue reaction (ALTR) presenting as a pseudotumor.

Question 87

A 70-year-old man with a well-functioning TKA placed 4 years ago presents with acute onset of severe knee pain, swelling, and fever 5 days after a dental procedure. Synovial aspiration shows 65,000 WBC/mcL with 95% neutrophils, and Gram stain reveals Gram-positive cocci. Radiographs demonstrate well-fixed components. What is the most appropriate surgical management?

Explanation

DAIR with polyethylene exchange is indicated for acute hematogenous periprosthetic joint infections (symptoms less than 3 weeks) with stable components. Two-stage revision is reserved for chronic infections or loose components.

Question 88

During templating for a primary THA, the surgeon plans to use a high-offset femoral stem instead of a standard-offset stem of the same neck length. How will this change affect the hip biomechanics?

Explanation

Using a high-offset stem increases femoral offset and the abductor moment arm, which improves abductor mechanical advantage and reduces joint reaction forces. High offset options generally do not affect leg length compared to a standard stem.

Question 89

During a primary TKA utilizing measured resection techniques, the surgeon evaluates the trial components. The knee is perfectly balanced and stable in extension but demonstrates severe laxity in flexion. What is the most appropriate step to balance the knee?

Explanation

A knee that is balanced in extension but loose in flexion has an isolated wide flexion gap. Upsizing the femoral component increases the AP dimension, tightening the flexion gap without affecting the extension gap.

Question 90

A 78-year-old woman sustains a closed supracondylar femur fracture above a posterior-stabilized TKA. Radiographs show a displaced fracture (Su/Rorabeck Type II), but the femoral component remains perfectly aligned and well-fixed. What is the optimal surgical treatment?

Explanation

For periprosthetic distal femur fractures with a well-fixed TKA component and adequate bone stock, open reduction and internal fixation (e.g., lateral locking plate or retrograde nail) is the standard of care. Distal femoral replacement is reserved for loose components or non-reconstructable bone.

Question 91

To minimize the risk of dislocation after a primary total hip arthroplasty, the acetabular component should ideally be placed within the Lewinnek safe zone. Which of the following target ranges defines this historical safe zone?

Explanation

The Lewinnek safe zone historically describes an optimal acetabular component position of 40° ± 10° for inclination and 15° ± 10° for anteversion to minimize the risk of postoperative dislocation.

Question 92

A 74-year-old woman undergoes a revision THA. Intraoperatively, she is found to have complete absence of the abductor musculature with severe fatty atrophy. Following placement of the revision components, the hip demonstrates significant instability and dislocates with minimal adduction. Which of the following is the most appropriate management?

Explanation

In the setting of severe or complete abductor deficiency causing intraoperative instability, a constrained acetabular liner is indicated to prevent dislocation. Dual mobility relies on dynamic soft-tissue stabilizers and may still fail in the complete absence of abductors.

Orthopedic Surgery Board Review MCQs: Arthroplasty, Trauma & Spine Part 255

Orthopedic Surgery Board Review MCQs: Adult Reconstruction, Hip & Knee Arthroplasty & Infection | Part 9

Key Takeaway

Orthopedic Surgery Board Review MCQs: Adult Reconstruction, Hip & Knee Arthroplasty & Infection | Part 9

Chapter Index