OITE & ABOS Orthopedic Board Prep MCQs: Part 90

Question 1

A 65-year-old male presents with groin pain 5 years after a primary metal-on-polyethylene total hip arthroplasty. Laboratory analysis shows elevated serum cobalt levels and normal chromium levels. Hip aspiration is negative for infection. What is the most likely source of the elevated metal ions?

Explanation

Elevated cobalt out of proportion to chromium in the setting of a non-metal-on-metal bearing (e.g., metal-on-polyethylene) is highly suggestive of mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction.

Question 2

During a total knee arthroplasty, which of the following component malpositions is most likely to result in lateral patellar tracking and potential subluxation?

Explanation

Internal rotation of the femoral component and internal rotation of the tibial component both increase the Q angle, leading to lateral patellar tracking and potential subluxation. Medialization of the femoral component and medialization of the patellar component also worsen lateral tracking.

Question 3

According to consensus criteria, which of the following is the most appropriate indication for debridement, antibiotics, and implant retention (DAIR) in a patient with a periprosthetic joint infection following TKA?

Explanation

DAIR is indicated for acute postoperative infections (typically < 4 weeks from surgery) or acute hematogenous infections (typically < 3-4 weeks of symptom onset) in the setting of well-fixed components and a healthy soft-tissue envelope. Chronic sinus tracts and loose components are absolute contraindications to DAIR.

Question 4

A 45-year-old active male presents with medial compartment osteoarthritis of the knee and 8 degrees of varus alignment. A medial opening wedge high tibial osteotomy (HTO) is planned. To maintain the native posterior tibial slope during the osteotomy, the surgeon should:

Explanation

The proximal tibia has a triangular shape in the axial plane. To maintain the native posterior slope during a medial opening wedge HTO, the posterior gap must be opened approximately twice as much as the anterior gap. Opening them equally will inadvertently increase the posterior tibial slope.

Question 5

In reverse total shoulder arthroplasty, placing the glenosphere with an inferior tilt rather than neutral or superior tilt achieves which of the following biomechanical advantages?

Explanation

Inferior tilt of the glenosphere in RTSA converts deleterious superior shear forces into compressive forces, improving baseplate fixation. It also helps decrease the rate of inferior scapular notching by providing better clearance.

Question 6

A 55-year-old woman undergoes a primary THA using a ceramic-on-ceramic bearing. Two years later, she complains of an audible squeaking sound from her hip during walking, without associated pain. Radiographs show well-fixed components. Which of the following is most strongly associated with the development of squeaking in ceramic-on-ceramic THA?

Explanation

Squeaking in ceramic-on-ceramic THA is most commonly associated with edge loading, which typically occurs due to component malposition (e.g., excessive cup anteversion, excessive cup abduction, or extreme combinations causing microseparation during gait).

Question 7

During a cruciate-retaining TKA, the surgeon notes that the knee is well balanced in extension but is tight in flexion, demonstrating restricted flexion and anterior liftoff of the tibial trial tray. Which of the following is the most appropriate next step to balance the knee?

Explanation

A tight flexion gap with a balanced extension gap in a cruciate-retaining TKA, characterized by anterior liftoff of the tibial tray, is often caused by a tight posterior cruciate ligament (PCL). Releasing or recessing the PCL will increase the flexion gap without affecting the extension gap.

Question 8

A 72-year-old female presents after a fall with a spiral fracture around her cementless THA stem. The stem has subsided 1.5 cm compared to previous radiographs. Bone stock is deemed adequate. According to the Vancouver classification, what is the most appropriate management?

Explanation

This is a Vancouver B2 periprosthetic femur fracture (fracture around the stem, loose stem, adequate bone stock). The gold standard management is revision of the femoral component using a long uncemented diaphyseal-engaging stem (fluted, tapered) to bypass the fracture site by at least two cortical diameters.

Question 9

In a revision total hip arthroplasty for a patient with massive acetabular bone loss, what radiographic finding best differentiates a pelvic discontinuity from a severe but continuous defect?

Explanation

Pelvic discontinuity is defined as a complete separation of the superior pelvis (ilium) from the inferior pelvis (ischium and pubis). The pathognomonic radiographic sign is a visible transverse fracture line extending completely through both the anterior and posterior columns.

Question 10

To optimize stability and minimize impingement in THA, the concept of combined anteversion is often utilized. If the acetabular cup is placed in 15 degrees of anteversion, what is the ideal target for femoral stem anteversion to achieve a standard combined anteversion of 35-40 degrees?

Explanation

Combined anteversion is the sum of cup anteversion and femoral stem anteversion. The classic target range (Ranawat/Dorr) is 25-45 degrees. If the cup is at 15 degrees, a femoral anteversion of 20-25 degrees will achieve a combined anteversion of 35-40 degrees, providing optimal stability.

Question 11

A 68-year-old man who underwent primary TKA 4 years ago presents with an inability to actively extend his knee following a fall. Clinical exam reveals a palpable gap at the superior pole of the patella. What is the most reliable surgical option for reconstruction of this chronic extensor mechanism disruption?

Explanation

Chronic or severe extensor mechanism disruptions in the setting of a TKA (especially large quadriceps defects or patellar tendon avulsions) have high failure rates with primary repair. Extensor mechanism allograft reconstruction or synthetic mesh reconstruction are the most reliable options to restore continuity.

Question 12

A patient is scheduled for a TKA. Radiographs show a healed midshaft femur fracture with a 15-degree coronal plane varus deformity. If an intra-articular bone resection is performed strictly perpendicular to the mechanical axis of the femur to correct alignment, what is the most likely consequence?

Explanation

In the presence of a diaphyseal femoral varus deformity, the mechanical axis deviates medially. To cut perpendicular to this mechanical axis intra-articularly, the surgeon must resect a larger amount of bone from the lateral distal femur. This leads to relative lateral collateral ligament laxity in extension.

Question 13

During a direct anterior approach for total hip arthroplasty, the superficial internervous plane utilized is between muscles innervated by which of the following nerves?

Explanation

The direct anterior approach (Smith-Petersen) utilizes the superficial internervous plane between the tensor fasciae latae (innervated by the superior gluteal nerve) and the sartorius (innervated by the femoral nerve).

Question 14

A 58-year-old woman presents with persistent, unexplained pain and swelling in her knee 2 years after a primary TKA. Joint aspiration is negative for infection. A synovial biopsy demonstrates a perivascular lymphocytic infiltrate with macrophages containing metal wear debris. Which of the following is the most likely diagnosis?

Explanation

ALVAL is a delayed-type hypersensitivity reaction to metal ions. It is characterized histologically by a perivascular lymphocytic infiltrate. It is a diagnosis of exclusion after infection and mechanical failure have been definitively ruled out.

Question 15

Which of the following is an absolute indication for using a rotating-hinge prosthesis rather than a constrained condylar knee (CCK) during a revision TKA?

Explanation

A constrained condylar knee (CCK) relies on the presence of at least one competent collateral ligament (typically the MCL) to function without early catastrophic failure. If both the MCL and LCL are deficient (global coronal instability), a rotating-hinge prosthesis is required.

Question 16

A 65-year-old male with a B2 glenoid (posterior wear, retroversion of 20 degrees) is undergoing anatomic total shoulder arthroplasty. What is the maximum amount of retroversion correction that should be attempted with eccentric anterior reaming alone before unacceptably compromising glenoid vault bone stock?

Explanation

Eccentric reaming is typically limited to correcting up to 10-15 degrees of retroversion. Reaming beyond 15 degrees removes excessive subchondral bone, narrowing the glenoid vault and compromising the fixation of the glenoid component.

Question 17

Metal-on-metal hip resurfacing is considered as an alternative to THA in select young, active patients. Which of the following is a recognized absolute contraindication for this procedure?

Explanation

Hip resurfacing relies heavily on the structural integrity of the femoral head and neck. Avascular necrosis with significant involvement (> 30-50% or large cysts) compromises the femoral bone stock, unacceptably increasing the risk of early femoral neck fracture, making it an absolute contraindication.

Question 18

A 70-year-old female with long-standing ankylosing spondylitis and a completely fused lumbar spine is undergoing a primary THA. How does her lack of spino-pelvic mobility dictate the optimal intraoperative positioning of her acetabular component to prevent dislocation?

Explanation

A normal spine allows the pelvis to tilt posteriorly during sitting, dynamically increasing functional acetabular anteversion and preventing anterior impingement. A fused spine fails to tilt posteriorly. To compensate and prevent posterior dislocation while seated, the cup must be placed in a higher degree of anteversion than standard.

Question 19

A patient develops severe true patella baja following a previous high tibial osteotomy and now requires a TKA. During the procedure, the patella cannot be safely everted. What is the most appropriate surgical maneuver to improve exposure and prevent patellar tendon avulsion?

Explanation

True patella baja places the patellar tendon at high risk for avulsion during knee flexion and patellar eversion in TKA. A tibial tubercle osteotomy (TTO) provides excellent exposure, protects the tendon, and allows for proximal advancement of the tubercle to correct the baja during closure.

Question 20

In the native knee, femoral rollback (the posterior translation of the contact point of the femur on the tibia during flexion) is primarily driven by the tension of which of the following ligaments?

Explanation

Femoral rollback is primarily driven by the tension in the posterior cruciate ligament (PCL) as the knee flexes. This kinematic mechanism allows for increased knee flexion by clearing the posterior femoral condyles from impinging on the posterior tibia.

Question 21

A patient undergoes primary total knee arthroplasty. During trialing, the knee is perfectly balanced and stable in extension, but it is unacceptably tight in flexion. Which of the following is the most appropriate surgical step to achieve a balanced gap without altering extension?

Explanation

Decreasing the AP size of the femoral component increases the flexion gap space without affecting the distal femoral cut, thereby leaving the extension gap unchanged.

Question 22

Which of the following surgical factors is most strongly associated with the postoperative complication of 'squeaking' in a ceramic-on-ceramic total hip arthroplasty?

Explanation

Squeaking in ceramic-on-ceramic THA is most strongly associated with edge loading. This is typically caused by acetabular component malposition, such as excessive inclination or anteversion.

Question 23

A 62-year-old male presents with new-onset cardiomyopathy, peripheral neuropathy, and visual field changes 6 years after a revision total hip arthroplasty. Aspiration of the hip yields clear fluid with a low white blood cell count. Which of the following implant configurations is most likely responsible for his systemic symptoms?

Explanation

The patient's systemic symptoms describe arthroprosthetic cobaltism. In the absence of a metal-on-metal bearing, severe trunnionosis at the head-neck junction of a cobalt-chrome head on a titanium stem is a known source of toxic cobalt levels.

Question 24

According to classic and contemporary criteria, which of the following is considered an absolute contraindication to a medial unicompartmental knee arthroplasty (UKA)?

Explanation

Advanced osteoarthritis with exposed bone in the contralateral (lateral) compartment is an absolute contraindication for a medial UKA. High weight and asymptomatic PFJ chondromalacia are no longer considered absolute contraindications.

Question 25

A 68-year-old female presents with a painful catching sensation and an audible 'clunk' at 35 degrees of flexion as she extends her knee actively. She underwent a primary posterior-stabilized TKA 14 months ago. What is the underlying pathomechanics of this condition?

Explanation

Patellar clunk syndrome occurs in posterior-stabilized knees when a fibrous nodule forms on the undersurface of the quadriceps tendon and catches in the intercondylar notch of the femoral component during active extension.

Question 26

During a medial opening wedge high tibial osteotomy (HTO), the surgeon inadvertently distracts the anterior aspect of the osteotomy gap significantly more than the posterior aspect. What biomechanical consequence will this have on the knee?

Explanation

Distracting the anterior aspect of the osteotomy greater than the posterior aspect in a medial opening wedge HTO increases the posterior tibial slope. To maintain normal slope, the anterior gap should generally be half the size of the posterior gap.

Question 27

A 55-year-old male undergoes a primary THA via a direct anterior approach. Postoperatively, he notes a burning pain and numbness isolated to the anterolateral aspect of his operative thigh. Strength is fully intact. Injury to which nerve is the most likely cause?

Explanation

The lateral femoral cutaneous nerve (LFCN) is a purely sensory nerve at risk during the direct anterior approach to the hip. Injury results in meralgia paresthetica, characterized by numbness and dysesthesias over the anterolateral thigh.

Question 28

According to the 2018 International Consensus Meeting (ICM) criteria, which of the following findings is sufficient on its own to confirm the diagnosis of a periprosthetic joint infection?

Explanation

The major criteria for diagnosing periprosthetic joint infection (PJI) are the presence of a sinus tract communicating with the joint, or two positive periprosthetic cultures with phenotypically identical organisms. Either is sufficient for definitive diagnosis.

Question 29

A 70-year-old female undergoes TKA for a severe, rigid 20-degree valgus deformity. In the recovery room, she is unable to dorsiflex her ankle or extend her toes, and has numbness in the first web space of her foot. What is the most appropriate initial management step?

Explanation

Postoperative peroneal nerve palsy after correction of a severe valgus deformity is often due to traction. Initial management involves relieving tension on the nerve by removing constrictive dressings and flexing the knee.

Question 30

A 76-year-old female presents with a third episode of posterior dislocation following a primary THA. Radiographs show well-fixed, correctly positioned components. Intraoperatively, her abductor musculature is found to be completely avulsed, retracted, and irreparable. Which of the following is the most appropriate definitive management?

Explanation

In the setting of recurrent instability with properly positioned components and a severely deficient, irreparable abductor mechanism, a constrained acetabular liner is indicated. Dual mobility components rely on a functional abductor mechanism to prevent dislocation.

Question 31

During a primary total knee arthroplasty, the trial components are placed, and the knee is found to be stable in full extension but tight in 90 degrees of flexion. Which of the following modifications is the most appropriate surgical step to balance the knee?

Explanation

Downsizing the femoral component using an anterior referencing system resects more posterior femoral condylar bone, directly increasing the flexion gap. Resecting more distal femur or releasing the posterior capsule primarily affects the extension gap.

Question 32

A 72-year-old female sustains a periprosthetic femur fracture around a cementless THA.

Radiographs show a fracture at the level of the stem tip with evidence of stem subsidence, though the surrounding diaphyseal cortical thickness is well-preserved (>3 mm). What is the standard of care for this patient?

Explanation

This is a Vancouver B2 fracture, characterized by a loose stem in the setting of adequate bone stock. The standard of care is revision arthroplasty utilizing a long, diaphyseal-engaging stem that bypasses the fracture by at least two cortical diameters.

Question 33

A 55-year-old male is undergoing a total knee arthroplasty 10 years after a medial opening wedge high tibial osteotomy (HTO). What specific anatomic alterations are most likely present that will complicate the arthroplasty?

Explanation

A medial opening wedge HTO distal to the tibial tubercle elevates the joint line relative to the tubercle, causing a relative patella baja. It also commonly results in an unintended increase in the posterior tibial slope.

Question 34

A 65-year-old male with long-standing ankylosing spondylitis and a fully fused lumbar spine in a flattened (loss of lordosis) position requires a THA. How should the acetabular component position be adjusted to minimize the risk of posterior dislocation?

Explanation

Patients with a fused flatback lack normal spinopelvic mobility and cannot increase pelvic tilt when sitting, leading to relative acetabular retroversion and a high risk of posterior dislocation. Compensating by placing the cup in higher anteversion and inclination helps accommodate sitting clearance.

Question 35

A 62-year-old male with long-standing ankylosing spondylitis is planned for a primary total hip arthroplasty (THA). Radiographs show a completely fused lumbar spine to the sacrum. How does this spinopelvic stiffness affect optimal acetabular cup positioning compared to a patient with normal spinopelvic mobility?

Explanation

Patients with a stiff spinopelvic junction lack the normal posterior pelvic tilt when transitioning from standing to sitting. This lack of tilt fails to functionally increase acetabular anteversion, leading to anterior impingement and posterior dislocation; thus, more anteversion is often required.

Question 36

During a primary total knee arthroplasty (TKA) for a severe varus deformity, the medial compartment remains significantly tight in both flexion and extension after appropriate bone cuts and thorough osteophyte removal. Which of the following is the most appropriate next step in soft tissue release?

Explanation

For a tight medial gap in both flexion and extension during a varus TKA, the superficial MCL is the primary restraint. Gradual release via pie-crusting or controlled subperiosteal stripping is the preferred technique to achieve balance without causing iatrogenic instability.

Question 37

A 68-year-old female presents with progressive groin pain 6 years after a metal-on-polyethylene THA utilizing a modular titanium stem and cobalt-chrome head. Aspiration yields fluid with 2,500 WBC/uL (80% lymphocytes) and negative cultures. Serum cobalt is markedly elevated. What is the most appropriate definitive management?

Explanation

This patient has trunnionosis with an adverse local tissue reaction (ALVAL), characterized by elevated cobalt and lymphocytic synovial fluid with negative cultures. Treatment involves revising the head to a ceramic head with a titanium sleeve to bypass the damaged trunnion, provided the stem is well-fixed.

Question 38

Which of the following best describes the primary objective of caliper-measured kinematic alignment in total knee arthroplasty?

Explanation

Kinematic alignment aims to restore the patient's pre-arthritic native joint lines and alignment by co-aligning the implants with the three kinematic axes of the knee. This technique relies on measured resections matching implant thickness, rather than soft tissue releases to a neutral mechanical axis.

Question 39

A 45-year-old active male underwent a primary THA. Two years postoperatively, he complains of an audible squeaking noise with walking and bending, but denies pain. Radiographs show well-fixed, well-positioned components. Which bearing surface combination is most classically associated with this complication?

Explanation

Audible squeaking is a well-documented complication specific to ceramic-on-ceramic THA bearings. It is often benign but can be related to microseparation, edge loading, or impingement.

Question 40

A 65-year-old female complains of a painful catch and pop in her knee when extending from a flexed position, one year after a posterior-stabilized TKA. What is the most likely etiology of this classic symptom?

Explanation

Patellar clunk syndrome occurs in posterior-stabilized TKAs when a fibrous nodule forms at the superior pole of the patella and catches in the femoral intercondylar box during extension. Treatment typically involves arthroscopic debridement of the nodule.

Question 41

When correcting a complex multi-planar lower extremity deformity using a hexapod circular external fixator, what mathematically defines the origin from which all spatial corrections are generated by the software?

Explanation

In 6-axis spatial frame software, the reference ring (usually the proximal ring) defines the Cartesian coordinate system and serves as the mathematical origin for calculating strut lengths to reposition the moving ring.

Question 42

A 72-year-old female sustains a periprosthetic femur fracture around a cemented polished taper stem. Radiographs reveal a comminuted fracture around the tip of the stem. The stem is loose, and there is severe proximal femoral bone loss preventing adequate diaphyseal fixation. How is this classified and most appropriately managed?

Explanation

A fracture around the stem tip with a loose stem and poor bone stock is a Vancouver B3 fracture. The standard of care is revision arthroplasty bypassing the fracture using a modular fluted tapered stem or a proximal femoral replacement (megaprosthesis) if the bone loss is too severe.

Question 43

Historically, catastrophic subsurface oxidation and subsequent delamination of total knee arthroplasty polyethylene inserts were most strongly associated with which of the following manufacturing processes?

Explanation

Gamma irradiation in air produces free radicals that react with oxygen over time (shelf oxidation or in vivo), leading to chain scission, embrittlement, and catastrophic delamination wear. Modern polyethylene is sterilized in inert environments and/or remelted/annealed to eliminate free radicals.

Question 44

A 70-year-old male presents with inability to actively extend his knee 3 years following a primary TKA. Examination reveals a palpable gap at the patellar tendon. What is the most reliable reconstructive option for this chronic, massive disruption?

Explanation

Chronic extensor mechanism disruptions post-TKA have extremely high failure rates with direct repair. Synthetic mesh (Marlex) reconstruction or a complete extensor mechanism allograft are the gold standards for restoring function.

Question 45

Which of the following surgical modifications most significantly decreases the risk of postoperative dislocation in primary total hip arthroplasty?

Explanation

Increasing femoral head size increases the jump distance and improves the head-to-neck ratio, significantly reducing the risk of impingement and subsequent dislocation. The direct anterior and anterolateral approaches generally have comparable low baseline dislocation rates.

Question 46

In a 6-year-old child with late-onset infantile Blount's disease, radiographs show a severe depression of the medial tibial plateau and a medial physeal bar. What is the most appropriate surgical management?

Explanation

In advanced Blount's disease with a documented physeal bar (tether), simply performing an osteotomy or guided growth will fail because the tether prevents normal growth. The bar must be resected, and an osteotomy is usually required to correct the existing deformity.

Question 47

During preoperative templating for a total hip arthroplasty, the surgeon notes a 15 mm functional leg length discrepancy (affected side short) and a 10 mm anatomic true leg length discrepancy (affected side short). To avoid symptomatic over-lengthening postoperatively, the surgeon should aim to restore:

Explanation

The goal of THA is to restore true anatomic leg length. Functional leg length discrepancies are often due to pelvic obliquity from spine pathology or soft tissue contractures, which typically adapt over time; correcting to functional length leads to true anatomic over-lengthening.

Question 48

A 60-year-old female scheduled for primary TKA reports a severe blistering skin reaction to inexpensive jewelry. Patch testing confirms a severe nickel allergy. Which of the following femoral component materials is most appropriate to prevent a hypersensitivity reaction?

Explanation

Patients with severe, documented metal allergies (like nickel) should receive hypoallergenic implants. Oxidized zirconium (Oxinium) or purely titanium-based components contain minimal to no nickel and are considered safe alternatives to standard cobalt-chromium alloys.

Question 49

A 74-year-old female presents for revision THA. Radiographs demonstrate an inferiorly migrated acetabular component, a transverse radiolucent line across the posterior column, and an ilioischial line break. Intraoperatively, the superior and inferior hemi-pelves move independently. Which of the following is the most appropriate reconstructive technique?

Explanation

Independent movement of the superior and inferior hemi-pelves indicates pelvic discontinuity. Reconstructive options must stabilize the two halves, typically requiring a cup-cage construct, a custom triflange component, or highly porous metal augments with a distraction technique.

Question 50

When planning a corrective osteotomy for a diaphyseal angular deformity, placing the osteotomy and the hinge exactly at the Center of Rotation of Angulation (CORA) will mathematically result in:

Explanation

According to the rules of osteotomy planning (Paley's rules), when the osteotomy and the mechanical hinge are both placed at the CORA, the deformity corrects with pure angulation and no secondary translation.

Question 51

A 68-year-old female presents with recurrent episodes of anterior hip dislocation following a primary total hip arthroplasty. Her dislocations typically occur when she extends and externally rotates her hip while walking. Which of the following component malpositions is the most likely cause of this specific instability pattern?

Explanation

Excessive combined anteversion of the acetabular and femoral components leads to anterior instability. This typically occurs in extension and external rotation, as the components lever against each other anteriorly.

OITE & ABOS Orthopedic Exam MCQs: Trauma, Foot & Knee Board Review Part 132

OITE & ABOS Orthopedic Board Prep: Adult Reconstruction, Extremities & Deformity MCQs Part 90

Key Takeaway

OITE & ABOS Orthopedic Board Prep: Adult Reconstruction, Extremities & Deformity MCQs Part 90

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