OITE & ABOS Orthopedic MCQs: Hip & Knee Arthroplasty

Question 1

A 72-year-old female presents with thigh pain after a fall. She had a primary total hip arthroplasty 10 years ago. Radiographs demonstrate a periprosthetic fracture around the femoral stem. The stem is determined to be loose, but there is adequate proximal and distal bone stock.

What is the most appropriate management according to the Vancouver classification system?

Explanation

This is a Vancouver B2 fracture, which involves a loose stem with adequate bone stock. The standard and most appropriate treatment for Vancouver B2 fractures is revision of the femoral component to a longer uncemented stem that bypasses the fracture by at least two cortical diameters to achieve distal fixation, along with stabilization of the fracture.

Question 2

During a primary posterior-stabilized total knee arthroplasty, the trial components are placed and the knee's range of motion is assessed. The knee is noted to be excessively tight in both full extension and at 90 degrees of flexion. What is the most appropriate next intraoperative step to achieve proper balancing?

Explanation

When a total knee arthroplasty is tight in both flexion and extension, it indicates that both the extension gap and the flexion gap are too small. The tibia affects both gaps equally. Therefore, the most appropriate step is to either use a thinner polyethylene insert or resect more proximal tibia.

Question 3

The direct anterior approach (Smith-Petersen) to the hip is increasingly popular for total hip arthroplasty. This approach utilizes a true internervous and intermuscular plane. Deep dissection occurs between which of the following muscles?

Explanation

The direct anterior approach utilizes an internervous plane. Superficial dissection is between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). The deep dissection continues between the rectus femoris (femoral nerve) and the gluteus medius (superior gluteal nerve).

Question 4

In the evaluation of a persistently painful total knee arthroplasty, synovial fluid is aspirated and an alpha-defensin test is ordered.

What is the primary role and characteristic of alpha-defensin in this clinical context?

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. It is a highly sensitive and specific biomarker for diagnosing periprosthetic joint infection (PJI) from synovial fluid, and notably, its accuracy is not significantly altered by prior systemic antibiotic administration.

Question 5

According to the 2018 International Consensus Meeting (ICM) criteria for periprosthetic joint infection (PJI), which of the following findings is considered a major criterion that independently confirms the diagnosis of a PJI?

Explanation

The major criteria for diagnosing PJI (either of which confirms the diagnosis independently) include: 1) A sinus tract communicating with the prosthesis, or 2) The isolation of the same pathogen by culture from at least two separate tissue or fluid samples obtained from the affected joint.

Question 6

A 65-year-old female presents with a painful catching sensation and an audible 'clunk' in her knee when extending from a flexed position. She underwent a primary posterior-stabilized total knee arthroplasty 18 months ago.

What is the most likely etiology of her symptoms?

Explanation

Patellar clunk syndrome is a known complication of posterior-stabilized (PS) total knee arthroplasties. It occurs when a fibrosynovial nodule develops at the superior pole of the patella and catches in the intercondylar box of the femoral component during knee extension from a flexed position.

Question 7

Medial unicompartmental knee arthroplasty (UKA) offers a less invasive alternative to total knee arthroplasty for isolated medial compartment osteoarthritis. Which of the following is classically considered an absolute contraindication to performing a medial UKA?

Explanation

Inflammatory arthropathy, such as rheumatoid arthritis, is an absolute contraindication to unicompartmental knee arthroplasty because the systemic disease process will inevitably affect the remaining native compartments of the joint. Age, obesity, and asymptomatic patellofemoral changes are considered relative contraindications or acceptable depending on the specific patient.

Question 8

A 55-year-old male with a metal-on-metal total hip arthroplasty placed 8 years ago presents with worsening groin pain and a palpable anterior mass. Serum cobalt and chromium levels are significantly elevated. MRI reveals a solid and cystic mass communicating with the joint space. What is the most likely diagnosis?

Explanation

Adverse local tissue reaction (ALTR), also known as ALVAL or pseudotumor, is a recognized complication of metal-on-metal hip arthroplasties or trunnionosis. It is characterized by elevated metal ions, a heavy lymphocytic infiltrate, and the formation of solid or cystic masses that can cause pain and tissue destruction.

Question 9

During a primary total knee arthroplasty for a severe varus deformity, the surgeon proceeds with sequential medial releases. After initial osteophyte removal and deep medial collateral ligament (MCL) release, trial components are placed. The knee is noted to be well-balanced in flexion but remains significantly tight on the medial side in full extension.

Which specific structure should be released next to achieve balance?

Explanation

In a varus knee, sequential releases are performed to achieve balance. If the knee remains tight medially in extension but is balanced in flexion, the posteromedial corner (posteromedial capsule and semimembranosus) is tight and should be released. If the knee is tight in both flexion and extension, the superficial MCL is the primary target.

Question 10

Tranexamic acid (TXA) is widely used in orthopedic arthroplasty to minimize perioperative blood loss and reduce transfusion rates. What is the precise pharmacological mechanism of action of TXA?

Explanation

Tranexamic acid is an antifibrinolytic synthetic analog of the amino acid lysine. It reversibly and competitively binds to the lysine-binding sites on plasminogen, thus preventing the activation of plasminogen to plasmin, which ultimately inhibits the degradation of fibrin clots.

Question 11

A 45-year-old male who underwent a ceramic-on-ceramic total hip arthroplasty 3 years ago reports a new, loud 'squeaking' noise emanating from his hip during ambulation. He denies pain or instability. What biomechanical or surgical factor is most strongly associated with the development of squeaking in a ceramic-on-ceramic bearing surface?

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is a specific phenomenon most commonly associated with suboptimal component positioning (e.g., excessive or insufficient acetabular cup anteversion or inclination). This malposition leads to edge loading, disruption of fluid-film lubrication, and resultant squeaking.

Question 12

In total hip arthroplasty, the 'safe zone' for acetabular component placement described by Lewinnek is historically targeted to minimize the risk of postoperative dislocation.

What are the classically described target ranges for acetabular abduction (inclination) and anteversion in this zone?

Explanation

The Lewinnek safe zone for acetabular cup placement is classically defined as 40° ± 10° of abduction (inclination) and 15° ± 10° of anteversion. While modern literature recognizes that dislocations can still occur within this zone, it remains the standard foundational target in THA.

Question 13

A 78-year-old female sustains a closed Su Type II distal femur fracture superior to a well-fixed posterior-stabilized total knee arthroplasty (TKA). The femoral component has a closed-box design. Assuming closed reduction is possible, what is the most appropriate surgical management?

Explanation

Fractures above a well-fixed TKA require stable fixation to allow early mobilization. While retrograde nailing is an excellent option for many distal femur fractures, it is generally contraindicated or impossible through a posterior-stabilized TKA with a closed-box design because the intercondylar notch is physically obstructed. Therefore, open reduction and internal fixation with a lateral locking plate is the treatment of choice.

Question 14

During a primary total knee arthroplasty, trial components are inserted. Evaluation reveals that the knee is perfectly stable and balanced in full extension, but demonstrates excessive medial and lateral laxity at 90 degrees of flexion. What is the most appropriate surgical adjustment to correct this imbalance?

Explanation

A knee that is balanced in extension but loose in flexion indicates an excessively large flexion gap. To selectively tighten the flexion gap without altering the extension gap, the surgeon should upsize the femoral component (often requiring posterior augments to avoid overstuffing anteriorly). Using a thicker poly would incorrectly tighten the already balanced extension gap.

Question 15

A 65-year-old female undergoes a right total hip arthroplasty via a posterior approach. Postoperatively in the recovery room, she demonstrates a dense foot drop and diminished sensation over the dorsal aspect of her right foot and lateral leg.

Which of the following intraoperative factors is most commonly responsible for this specific nerve injury?

Explanation

The patient is exhibiting signs of a peroneal nerve palsy (a division of the sciatic nerve). The peroneal division is lateral and more firmly tethered, making it highly susceptible to traction injuries. The most common cause of sciatic nerve palsy after THA is excessive lengthening of the limb (typically >4 cm).

Question 16

A 75-year-old female undergoes fixation of an unstable, reverse obliquity intertrochanteric femur fracture with a standard sliding hip screw (dynamic hip screw). Six weeks later, radiographs show catastrophic cut-out of the lag screw and medialization of the femoral shaft. What is the primary biomechanical reason a sliding hip screw is relatively contraindicated for this specific fracture pattern?

Explanation

In reverse obliquity intertrochanteric fractures, the fracture line runs from proximal-medial to distal-lateral. A sliding hip screw allows controlled collapse along the axis of the lag screw. Because the sliding vector is nearly parallel to the fracture line, it causes the femoral shaft to medialize and the head/neck fragment to translate laterally, leading to nonunion and fixation failure. Cephalomedullary nails are biomechanically superior for this pattern.

Question 17

A 70-year-old male presents with severe anterior knee pain and a complete inability to actively extend his knee, occurring 3 years after a primary total knee arthroplasty. Imaging confirms a chronic, complete, and retracted patellar tendon rupture.

What is the most reliable reconstructive option given the chronic nature and poor tissue quality?

Explanation

Chronic, complete extensor mechanism disruptions following TKA are notoriously difficult to treat. Primary repair or simple autograft reconstructions have unacceptably high failure rates due to poor local tissue quality. The most reliable surgical treatment is an extensor mechanism allograft or a robust synthetic mesh reconstruction.

Question 18

A 68-year-old female with long-standing ankylosing spondylitis and a fully fused thoracolumbar spine is planned for a primary total hip arthroplasty. How does her stiff spinopelvic complex influence the preoperative planning for acetabular component positioning?

Explanation

Normally, moving from standing to sitting causes the pelvis to tilt posteriorly, increasing functional acetabular anteversion and accommodating hip flexion. Patients with fused spines (ankylosing spondylitis) cannot posteriorly tilt their pelvis, increasing the risk of anterior impingement and posterior dislocation when sitting. Therefore, the acetabular component should be placed in increased anteversion to compensate.

Question 19

A 30-year-old male sustains a vertically oriented, highly displaced femoral neck fracture (Pauwels type III). Which of the following internal fixation constructs provides the most biomechanical stability against the extreme shear forces present in this specific fracture pattern?

Explanation

Pauwels type III femoral neck fractures are highly vertically oriented, resulting in massive shear forces across the fracture site rather than compressive forces. Biomechanical studies demonstrate that a fixed-angle construct, such as a sliding hip screw (DHS) often supplemented with a derotational screw, provides superior biomechanical stability and higher load-to-failure against these shear forces compared to multiple parallel cancellous screws.

Question 20

During the femoral preparation of a primary total knee arthroplasty, the surgeon is utilizing a posterior referencing sizing guide.

The patient's anatomy falls exactly between sizes on the guide. If the surgeon elects to downsize the femoral component, what is the most likely geometric consequence?

Explanation

In a posterior referencing system, the posterior condylar cuts are kept constant regardless of component size to maintain the flexion gap. If the surgeon falls between sizes and downsizes the component, the anterior cut will be shifted posteriorly. This significantly increases the risk of creating a stress riser by notching the anterior femoral cortex.

Question 21

During a primary total knee arthroplasty, trial components are placed. The knee is symmetric and balanced in extension, but it is symmetrically tight in 90 degrees of flexion. Which of the following is the most appropriate intraoperative step to balance the knee?

Explanation

A tight flexion gap with a balanced extension gap is addressed by decreasing the AP diameter of the femoral component (downsizing) or increasing the posterior tibial slope. Downsizing the femur increases the flexion gap without altering the extension gap.

Question 22

A 78-year-old female presents with thigh pain and inability to bear weight after a mechanical fall. Radiographs demonstrate a periprosthetic femur fracture around the tip of her cemented total hip arthroplasty stem. The stem is grossly loose on imaging, and the proximal femoral bone stock is severely deficient with diaphyseal thinning.

What is the most appropriate surgical management?

Explanation

This describes a Vancouver B3 periprosthetic fracture, characterized by a loose stem and poor proximal bone stock. Management requires revision using a modular fluted tapered stem to bypass the deficient bone and achieve secure diaphyseal fixation.

Question 23

A 45-year-old male who underwent a ceramic-on-ceramic total hip arthroplasty 4 years ago complains of a loud squeaking noise from his hip with every step. He denies pain or instability. Which of the following is the most significant risk factor for this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic THA is heavily associated with stripe wear caused by edge loading. This most commonly results from component malposition, specifically excessive acetabular cup anteversion or inclination.

Question 24

Postoperatively, a patient who underwent a primary total knee arthroplasty complains of anterior knee pain and a feeling of instability. Radiographs demonstrate lateral patellar tilt and subluxation. Which of the following errors during component positioning most likely contributed to this finding?

Explanation

Internal rotation of either the femoral or tibial components increases the Q-angle, which displaces the extensor mechanism laterally. This leads to lateral patellar maltracking, subluxation, and anterior knee pain.

Question 25

A 55-year-old female with a metal-on-metal total hip arthroplasty presents with new-onset groin pain and a palpable anterior mass. Laboratory evaluation shows normal CRP and ESR. An MRI with MARS sequencing reveals a large cystic pseudotumor. What is the primary pathophysiology underlying this complication?

Explanation

Adverse local tissue reaction (ALVAL) in metal-on-metal hips is fundamentally a Type IV delayed hypersensitivity reaction to metal ions (cobalt and chromium), frequently presenting with a soft-tissue pseudotumor.

Question 26

A 70-year-old female sustains a supracondylar femur fracture 2 cm above the flange of her primary total knee arthroplasty. The femoral component is a posterior-stabilized, closed-box design and appears well-fixed. Which of the following is the most appropriate fixation strategy?

Explanation

A closed-box design of a posterior-stabilized femoral component physically blocks the insertion of a retrograde intramedullary nail. Consequently, lateral locked plating is the preferred fixation method for a periprosthetic fracture above a well-fixed, closed-box component.

Question 27

During a direct anterior (Smith-Petersen) approach for total hip arthroplasty, the surgeon performs deep dissection between the sartorius and tensor fasciae latae. Which nerve is at greatest risk of iatrogenic injury if dissection is carelessly carried too superficially in this interval?

Explanation

The lateral femoral cutaneous nerve (LFCN) is highly vulnerable during the superficial dissection of the direct anterior approach. It courses over the sartorius and can be injured, leading to meralgia paresthetica.

Question 28

A 65-year-old male presents with persistent pain 3 years after a primary total knee arthroplasty. Serum ESR is 45 mm/hr and CRP is 25 mg/L. Synovial fluid aspiration yields a WBC count of 4,500 cells/μL with 85% PMNs. What is the most appropriate next step in management?

Explanation

A synovial WBC > 3,000 cells/μL and PMN > 80% is strongly suspicious for chronic periprosthetic joint infection (PJI). Confirmatory testing with cultures and specific biomarkers (like alpha-defensin) is required before definitive revision surgery.

Question 29

A patient undergoes a primary total hip arthroplasty. Postoperative templating reveals that the femoral offset was decreased by 15 mm compared to the contralateral native hip. What is the most likely clinical consequence of this biomechanical alteration?

Explanation

Decreasing femoral offset reduces the lever arm of the abductor musculature. This forces the abductors to generate more force to stabilize the pelvis, increasing overall joint reactive forces and frequently resulting in abductor weakness (Trendelenburg gait).

Question 30

Revision of a 20-year-old total knee arthroplasty reveals severe destruction of the polyethylene insert. The implant records indicate the polyethylene was sterilized by gamma irradiation in air. Which of the following wear mechanisms is predominantly responsible for this failure?

Explanation

Polyethylene sterilized by gamma irradiation in an oxygen-rich environment (air) undergoes free radical formation and subsequent subsurface oxidation over time. This degrades the material properties, leading to catastrophic delamination wear.

Question 31

Six months after a posterior-stabilized total knee arthroplasty, a patient complains of a painful catching sensation in the knee when extending from a flexed position, specifically between 30 and 40 degrees of flexion. What is the most likely etiology?

Explanation

Patellar clunk syndrome occurs uniquely in posterior-stabilized TKAs. A fibrous nodule develops at the superior pole of the patella and catches in the intercondylar notch of the femoral component during extension, producing a painful 'clunk'.

Question 32

A patient sustains a fall 3 weeks after an uncomplicated primary total hip arthroplasty. Radiographs show a minimally displaced (<1 cm) fracture of the greater trochanter. The femoral stem remains perfectly aligned and well-fixed without evidence of subsidence. What is the most appropriate management?

Explanation

This is a Vancouver A (AG) periprosthetic fracture. Because it is minimally displaced and the stem is completely stable, it is best managed non-operatively with protected weight bearing and abduction precautions to allow healing.

Question 33

A 60-year-old patient presents for a 10-year follow-up after receiving a fully porous-coated, extensively fixed cylindrical stem total hip arthroplasty. Radiographs demonstrate excellent distal diaphyseal fixation but severe localized proximal medial bone resorption. The patient is entirely asymptomatic. What is the primary cause of this radiographic finding?

Explanation

Extensively porous-coated stems achieve rigid distal fixation, effectively bypassing the proximal femur for load transfer. According to Wolff's law, this lack of mechanical stress leads to adaptive bone resorption known as stress shielding.

Question 34

Fourteen days after an elective total hip arthroplasty, a patient returns with a fever of 101.5°F, escalating hip pain, and a draining, erythematous surgical wound. Radiographs show perfectly positioned, well-fixed components. What is the most appropriate initial surgical intervention?

Explanation

DAIR is the treatment of choice for acute postoperative periprosthetic joint infections (occurring within 3-4 weeks of the index procedure) when the implants are well-fixed and soft tissues are amenable to coverage. Modular components (like the femoral head and poly liner) must be exchanged.

Question 35

A 68-year-old male undergoes a primary total hip arthroplasty via a posterior approach. Postoperatively, he experiences recurrent posterior dislocations. Radiographs show the acetabular component at 40 degrees of abduction and 20 degrees of anteversion, and the femoral stem is well-fixed in 15 degrees of anteversion. Which of the following pre-existing conditions is the most significant risk factor for this patient's recurrent instability despite appropriate component positioning?

Explanation

A stiff lumbosacral spine (e.g., ankylosing spondylitis or prior fusion) impairs the pelvis's ability to tilt backward during sitting. This increases relative acetabular retroversion, significantly increasing the risk of posterior dislocation.

Question 36

A 68-year-old male is undergoing a total hip arthroplasty. The surgeon plans to use highly cross-linked polyethylene (HXLPE) to reduce wear. Which of the following manufacturing processes is critical to eliminate free radicals generated during the cross-linking process and prevent in vivo oxidative degradation?

Explanation

Remelting (heating above the melting point) or annealing (heating below the melting point) eliminates free radicals generated by gamma irradiation. This is crucial for preventing long-term oxidative degradation of the polyethylene.

Question 37

During a primary posterior-stabilized total knee arthroplasty, the knee is balanced in extension but is found to be excessively tight in flexion, preventing full range of motion. The extension gap is symmetric and perfectly tensioned. Which of the following is the most appropriate step to correct this kinematic mismatch?

Explanation

A tight flexion gap with a balanced extension gap implies the anteroposterior dimension of the femoral component is too large. Downsizing the femoral component (which decreases the posterior condylar offset) or increasing the posterior tibial slope will increase the flexion gap without affecting the extension gap.

Question 38

A 78-year-old female sustains a periprosthetic femur fracture around her cementless total hip arthroplasty after a fall. Radiographs demonstrate a fracture around the tip of the stem. The stem is radiographically loose, and there is significant proximal osteolysis with poor bone stock in the proximal metaphysis. Which of the following is the most appropriate management (Vancouver Type B3)?

Explanation

A Vancouver B3 fracture involves a loose stem and inadequate proximal bone stock. Proximal femoral replacement or a long modular fluted tapered stem with structural allograft are the preferred treatments to bypass the deficient bone and achieve stability.

Question 39

Which of the following biomechanical changes most effectively decreases the joint reactive force across the hip during a single-leg stance following a total hip arthroplasty?

Explanation

Increasing the abductor moment arm (typically by increasing femoral offset) provides a mechanical advantage to the abductor muscles. This reduces the force required by the abductors to maintain the pelvis level, thereby decreasing the overall joint reactive force.

Question 40

A 65-year-old female presents with a painful clunking sensation in her knee when extending from a flexed position. She underwent a posterior-stabilized total knee arthroplasty 18 months ago. Examination reveals a palpable catch at approximately 40 degrees of flexion. Which of the following is the underlying pathophysiology of this condition?

Explanation

Patellar clunk syndrome occurs in posterior-stabilized TKA designs when a fibrous nodule forms at the superior pole of the patella. This nodule catches in the intercondylar box of the femoral component during extension from a flexed position.

Question 41

In a patient undergoing revision total hip arthroplasty, the surgeon encounters severe pelvic discontinuity. Radiographs and intraoperative findings show complete separation of the superior and inferior hemipelvis. Which of the following surgical constructs is generally considered the most reliable for achieving stability and long-term fixation in this scenario?

Explanation

Pelvic discontinuity requires rigid stabilization between the superior and inferior halves of the pelvis. A cup-cage construct or a custom triflange component bridges the defect and provides mechanical stability to allow for potential biologic fixation or bridging bone formation.

Question 42

When balancing a severe varus deformity during a primary total knee arthroplasty, the surgeon performs a sequential medial release. After releasing the deep medial collateral ligament (MCL) and removing osteophytes, the knee remains tight medially in extension but balanced in flexion. Which structure should be released next to correct the medial tightness in extension?

Explanation

The posteromedial corner (posteromedial capsule and semimembranosus insertions) primarily affects the extension gap. Releasing these structures will correct medial tightness in extension without significantly affecting the flexion gap.

Question 43

A 55-year-old male presents with acute onset of severe left knee pain 14 days after a primary total knee arthroplasty. The knee is swollen, erythematous, and warm. Aspiration yields purulent synovial fluid with a white blood cell count of 65,000 cells/uL (95% neutrophils). What is the most appropriate surgical management?

Explanation

For acute periprosthetic joint infections occurring within 4 weeks of the index procedure and involving a well-fixed implant, Debridement, Antibiotics, and Implant Retention (DAIR) with a modular component exchange is the standard of care.

Question 44

A patient with a metal-on-metal total hip arthroplasty presents 5 years postoperatively with groin pain and a palpable mass. MRI with metal artifact reduction sequence (MARS) reveals a large cystic lesion adjacent to the joint. Histology from a subsequent revision surgery shows a perivascular lymphocytic infiltrate. This reaction is best classified as which type of hypersensitivity?

Explanation

Aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) or adverse local tissue reactions (ALTR) in metal-on-metal hips are characterized by a perivascular lymphocytic infiltrate. This represents a Type IV (delayed, cell-mediated) hypersensitivity reaction to metal ions.

Question 45

An 82-year-old male sustains a closed supracondylar femur fracture just proximal to his total knee arthroplasty (Lewis-Rorabeck Type II). The femoral component is well-fixed, and there is no evidence of osteolysis. Which of the following is the most appropriate surgical treatment?

Explanation

A Lewis-Rorabeck Type II periprosthetic distal femur fracture features a displaced fracture with a well-fixed femoral component. The gold standard treatment is internal fixation, typically achieved using lateral locked plating or a retrograde intramedullary nail (if the femoral component box allows).

Question 46

During a total knee arthroplasty, optimizing patellofemoral tracking is crucial. Which of the following technical errors most strongly predisposes the patella to track laterally and potentially subluxate or dislocate?

Explanation

Internal rotation of the femoral component medializes the trochlear groove relative to the extensor mechanism, significantly increasing the Q-angle and predisposing the patella to lateral tracking and subluxation.

Question 47

A 70-year-old active female undergoes a total hip arthroplasty via a posterior approach for a displaced femoral neck fracture. Compared to a bipolar hemiarthroplasty for the same indication, which of the following outcomes is most associated with total hip arthroplasty?

Explanation

In active elderly patients with displaced femoral neck fractures, THA provides better functional scores and lower long-term reoperation rates compared to hemiarthroplasty. However, THA is associated with a higher initial dislocation rate.

Question 48

Which of the following is considered an absolute contraindication for a medial unicompartmental knee arthroplasty (UKA)?

Explanation

Inflammatory arthropathies (e.g., Rheumatoid arthritis) are absolute contraindications for unicompartmental knee arthroplasty due to the systemic, progressive nature of the joint destruction. Intact ACL is actually a prerequisite for UKA.

Question 49

A surgeon encounters a well-fixed, proximally porous-coated femoral stem that must be removed for a recurrent periprosthetic joint infection. To facilitate extraction while minimizing catastrophic bone loss, the surgeon plans an extended trochanteric osteotomy (ETO). What is the optimal location and length for the osteotomy?

Explanation

An extended trochanteric osteotomy (ETO) is typically performed on the anterolateral aspect of the femur, leaving the posterior structures (linea aspera and muscular attachments) intact as a hinge. It should extend just distal to the well-fixed portion (porous coating) to allow stem extraction.

Question 50

A patient with a large-diameter metal-on-polyethylene total hip arthroplasty presents with unexplained hip pain 4 years postoperatively. Radiographs show a well-fixed implant with a short, thin femoral trunnion. Serum cobalt levels are highly elevated, while chromium is normal. What is the most likely diagnosis?

Explanation

Trunnionosis is mechanically assisted crevice corrosion at the modular head-neck junction. It is characterized by elevated serum cobalt levels (often disproportionate to chromium) and ALTR, particularly associated with large head sizes and small/short trunnions.

Question 51

Regarding the kinematics of the native knee and its replication in total knee arthroplasty (TKA), what is the primary biomechanical function of femoral rollback during deep flexion?

Explanation

Femoral rollback (posterior translation of the femoral condyles on the tibia during flexion) clears the posterior aspect of the femur from impinging on the posterior tibia, allowing for greater flexion. It also improves the quadriceps moment arm.

Question 52

A 45-year-old male with end-stage avascular necrosis undergoes a primary total hip arthroplasty. The surgeon uses the direct anterior (Smith-Petersen) approach. Which of the following nerve injuries is most specifically associated with the superficial dissection of this approach?

Explanation

The direct anterior approach uses the internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). The lateral femoral cutaneous nerve courses superficially over the sartorius and is at highest risk during the superficial dissection.

Question 53

A 79-year-old male is scheduled for a total hip arthroplasty. He has a history of severe heterotopic ossification (HO) following a contralateral THA. Which of the following prophylactic regimens is most appropriate to prevent HO in this patient?

Explanation

Prophylaxis for heterotopic ossification in high-risk patients typically involves either a single fraction of external beam radiation (700-800 cGy) given preoperatively or immediately postoperatively, or an oral NSAID such as Indomethacin for 2-6 weeks.

Question 54

When setting femoral rotation during a primary total knee arthroplasty, the surgeon aligns the epicondylar axis. If the surgeon mistakenly references the posterior condylar axis in a severely valgus knee with lateral femoral condyle hypoplasia without compensating for it, what is the most likely error?

Explanation

In a valgus knee, the lateral posterior condyle is often hypoplastic. Using a standard 3 degrees of external rotation off the posterior condylar axis (PCA) without accounting for this hypoplasia will result in excessive internal rotation of the femoral component.

Question 55

A 72-year-old woman presents with persistent, disabling knee stiffness 8 weeks after a primary total knee arthroplasty. Her active range of motion is 15 to 65 degrees. Physical therapy has failed to improve her motion. Radiographs show well-positioned components without loosening. What is the most appropriate next step in management?

Explanation

Manipulation under anesthesia (MUA) is most successful when performed within the first 12 weeks after TKA for refractory stiffness. Waiting beyond 12 weeks decreases the success rate and increases the risk of complications such as supracondylar femur fracture.

Question 56

A patient presents with a recurrent knee effusion and a feeling of "giving way" when descending stairs 1 year after a posterior-stabilized TKA. Radiographs show well-fixed components. Physical exam reveals increased anteroposterior laxity at 90 degrees of flexion but stability in full extension. What intraoperative error most likely caused this isolated flexion instability?

Explanation

Excessive resection of the posterior femoral condyles abnormally increases the flexion gap without affecting the extension gap. This leads to flexion instability, classically presenting with poor stair descent and recurrent effusions.

Question 57

A 45-year-old male complains of a high-pitched, audible squeaking from his hip during walking 3 years after a primary total hip arthroplasty. Radiographs show well-fixed components with a cup abduction angle of 55 degrees. Which combination of bearing surfaces is most associated with this clinical phenomenon?

Explanation

Squeaking is a known complication specific to ceramic-on-ceramic bearings. It is often associated with edge loading due to component malposition, such as excessive acetabular cup abduction or version.

Question 58

When evaluating a painful total knee arthroplasty for potential periprosthetic joint infection, which of the following synovial fluid biomarkers acts by binding to microbial cell membranes, forming pore-like defects, and offers exceptionally high sensitivity and specificity?

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils that kills pathogens by disrupting their cell membranes. It is a highly accurate biomarker for diagnosing periprosthetic joint infection, largely unaffected by concurrent antibiotic use.

Question 59

A 78-year-old female presents with a periprosthetic femur fracture 12 years after a primary THA. Radiographs reveal a fracture around a loose femoral stem with severe comminution and nearly completely deficient proximal bone stock extending to the diaphysis. According to the Vancouver classification, what is the most appropriate surgical treatment?

Explanation

This is a Vancouver B3 fracture, defined by a fracture around a loose stem with severely deficient proximal bone stock. Proximal femoral replacement or a severely augmenting salvage technique is typically required.

Question 60

During a primary total knee arthroplasty, the surgeon accidentally internally rotates the femoral component 5 degrees relative to the surgical epicondylar axis. What is the most likely biomechanical consequence of this positioning error?

Explanation

Internal rotation of the femoral component translates the trochlear groove medially, effectively increasing the Q-angle. This increases the lateral subluxation forces on the patella, leading to lateral tilt and potential dislocation.

Question 61

A surgeon is performing a primary THA via the direct anterior (Smith-Petersen) approach. During the deep dissection between the tensor fasciae latae and sartorius, a vascular bundle is routinely encountered crossing the field that must be ligated to prevent excessive bleeding. This bundle represents branches of which of the following arteries?

Explanation

The ascending branches of the lateral femoral circumflex artery reliably cross the internervous plane of the direct anterior approach. Ligation or cauterization is necessary to maintain hemostasis.

Question 62

A 68-year-old male sustains a supracondylar femur fracture just above a posterior-stabilized total knee arthroplasty. Radiographs confirm the fracture is displaced but the femoral component remains rigidly fixed with no osteolysis. What is the preferred surgical treatment?

Explanation

This describes a Lewis-Rorabeck Type II fracture (displaced fracture with a well-fixed prosthesis). The gold standard treatment is osteosynthesis, typically with a lateral locking plate that spans the fracture and avoids the component.

Question 63

What anatomic or mechanical feature primarily drives posterior femoral rollback during deep flexion in a cruciate-retaining (CR) total knee arthroplasty?

Explanation

In a CR total knee arthroplasty, the posterior cruciate ligament (PCL) is retained and its tension primarily drives femoral rollback. In a posterior-stabilized (PS) design, rollback is achieved mechanically via cam-post engagement.

Question 64

A 65-year-old female presents with recurrent anterior dislocations of her total hip arthroplasty. Intraoperative evaluation during revision reveals that the well-fixed acetabular component is in 35 degrees of anteversion, and the well-fixed femoral stem is in 20 degrees of anteversion. What is the most appropriate management?

Explanation

Combined anteversion in THA should ideally be between 25 and 45 degrees. With a combined anteversion of 55 degrees, the patient is highly prone to anterior dislocation, and revising the cup to decrease anteversion addresses the source of instability.

Question 65

A patient develops a diffuse, eczematous dermatitis over the surgical knee and progressive joint stiffness 6 months following a primary TKA. Infection is definitively ruled out. Patch testing confirms a severe nickel allergy. The pathogenesis of this reaction is best described as:

Explanation

Metal hypersensitivity (such as nickel allergy) following arthroplasty represents a Type IV delayed hypersensitivity reaction. It is mediated by antigen-specific T-cells rather than antibodies.

Question 66

Which of the following design factors has been most strongly associated with an increased risk of mechanically assisted crevice corrosion (trunnionosis) at the head-neck junction in total hip arthroplasty?

Explanation

Large-diameter cobalt-chromium femoral heads increase the lever arm and torque forces at the modular head-neck junction (trunnion). This significantly increases the risk of fretting and crevice corrosion (trunnionosis).

Question 67

A 70-year-old male presents with a complete, chronic rupture of the patellar tendon 3 months after a primary TKA. He cannot actively extend his knee against gravity. Primary repair is impossible due to tissue retraction. What is the most reliable surgical reconstruction technique?

Explanation

Chronic or irreparable patellar tendon ruptures in the setting of TKA are exceptionally difficult to manage. Extensor mechanism allograft (often utilizing an Achilles tendon with bone block or a whole extensor mechanism) or synthetic mesh reconstruction provides the most reliable restoration of function.

Question 68

Which of the following is classically considered an absolute contraindication to performing a medial unicompartmental knee arthroplasty (UKA)?

Explanation

Inflammatory arthropathies (e.g., rheumatoid arthritis) involve the entire synovium and affect all joint compartments, making partial joint replacement inappropriate. UKA is contraindicated due to the high risk of rapid progression in the retained compartments.

Question 69

A patient complains that their operative leg feels longer after a primary THA. Clinical examination reveals the distance from the umbilicus to the medial malleolus is equal bilaterally, but the distance from the anterior superior iliac spine (ASIS) to the medial malleolus is 2 cm longer on the operative side. Which of the following best explains these findings?

Explanation

Measurements from the ASIS to the medial malleolus evaluate true leg length, while measurements from the umbilicus to the medial malleolus evaluate apparent leg length. A longer ASIS-malleolus distance confirms a true leg length discrepancy, with pelvic tilt masking the apparent length.

Question 70

Which of the following preoperative patient characteristics is statistically the most significant independent risk factor for deep wound infection and poor wound healing following total knee arthroplasty?

Explanation

Poorly controlled diabetes (HbA1c > 8.0%) dramatically increases the risk of periprosthetic joint infection and impaired wound healing. Strict preoperative glycemic control is universally recommended for risk mitigation.

Question 71

Tranexamic acid (TXA) is routinely utilized in total joint arthroplasty to minimize perioperative blood loss. Which of the following describes its precise pharmacological mechanism of action?

Explanation

Tranexamic acid is a synthetic analog of the amino acid lysine. It competitively inhibits the activation of plasminogen to plasmin, thereby preventing the degradation of fibrin clots (antifibrinolytic effect).

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

OITE & ABOS Orthopedic Board Exam MCQs: Hip & Knee Arthroplasty, Fracture | Part 196

Key Takeaway

OITE & ABOS Orthopedic Board Exam MCQs: Hip & Knee Arthroplasty, Fracture | Part 196

Chapter Index