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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 176 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 3501

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male sustains a posterior dislocation of his total hip arthroplasty while bending to tie his shoes 6 weeks postoperatively. Radiographs demonstrate a well-fixed cup with 45 degrees of inclination and 5 degrees of retroversion. The femoral stem is anteverted by 10 degrees. What is the most likely primary cause of the dislocation?

. Insufficient acetabular inclination
. Insufficient combined anteversion
. Impingement of the greater trochanter on the ilium
. Insufficient femoral offset
. Excessive combined anteversion

Correct Answer & Explanation

. Insufficient combined anteversion

Explanation

The patient's cup is retroverted by 5 degrees (-5 degrees anteversion) and the stem is anteverted by 10 degrees, resulting in a combined anteversion of only 5 degrees. The normal target for combined anteversion is typically between 25 and 45 degrees to prevent impingement and dislocation. This critically low combined anteversion makes the construct highly prone to anterior impingement in flexion and subsequent posterior dislocation.

Question 3502

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female undergoes a right total knee arthroplasty for severe valgus osteoarthritis. Postoperatively, she is unable to actively dorsiflex her right ankle or extend her toes, and she has decreased sensation over the dorsum of her foot. Which of the following intraoperative factors is most closely associated with this complication?

. Over-resection of the distal femur
. Excessive internal rotation of the tibial component
. Correction of a severe fixed valgus deformity
. Use of a constrained non-hinged polyethylene insert
. Release of the medial collateral ligament

Correct Answer & Explanation

. Correction of a severe fixed valgus deformity

Explanation

The patient has a common peroneal nerve palsy, which is a well-documented complication of TKA, particularly following the correction of a severe, long-standing valgus deformity often combined with a flexion contracture. The acute correction stretches the contracted lateral structures, placing tension on the peroneal nerve.

Question 3503

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty utilizing a measured resection technique, the surgeon aims to establish a balanced rectangular flexion gap. If the femoral component is inadvertently placed in excessive internal rotation relative to the transepicondylar axis, what is the expected effect on the flexion gap?

. Tight medial in flexion, loose lateral in flexion
. Loose medial in flexion, tight lateral in flexion
. Tight medial in flexion, tight lateral in flexion
. Loose medial in flexion, loose lateral in flexion
. Symmetric tightening of both medial and lateral gaps

Correct Answer & Explanation

. Tight medial in flexion, loose lateral in flexion

Explanation

In measured resection TKA, placing the femoral component in internal rotation relative to the transepicondylar axis results in under-resection of the posterior medial femoral condyle and over-resection of the posterior lateral femoral condyle. The thicker retained bone on the medial side causes the medial flexion gap to be tight, while the lateral flexion gap becomes loose.

Question 3504

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male presents with a painful total knee arthroplasty 3 years after the index procedure. Radiographs show no component loosening. Joint aspiration yields a synovial white blood cell (WBC) count of 4,200 cells/ยตL with 88% polymorphonuclear leukocytes (PMNs). Which of the following synovial fluid biomarkers has the highest specificity for diagnosing a periprosthetic joint infection (PJI)?

. Interleukin-6 (IL-6)
. C-reactive protein (CRP)
. Alpha-defensin
. Leukocyte esterase
. Procalcitonin

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to infection. It has been shown to have an extremely high specificity (often >95%) and sensitivity for diagnosing periprosthetic joint infections (PJI), outperforming other synovial markers such as CRP, IL-6, and leukocyte esterase, making it highly valuable in diagnostic algorithms.

Question 3505

Topic: 3. Adult Reconstruction (Hip & Knee)

A 79-year-old woman sustains a fall 8 years following a primary total hip arthroplasty. Radiographs demonstrate a displaced periprosthetic fracture of the femur just distal to the tip of the stem. The stem appears radiographically loose, but there is excellent proximal and distal bone stock.

What is the most appropriate surgical management?

. Open reduction and internal fixation with cerclage cables alone
. Open reduction and internal fixation with a laterally applied locking plate
. Revision to a fully porous-coated cylindrical long stem
. Revision to a modular fluted tapered stem
. Proximal femoral replacement

Correct Answer & Explanation

. Revision to a modular fluted tapered stem

Explanation

This is a Vancouver B2 periprosthetic femur fracture (fracture around or just below the stem, loose stem, good bone stock). The standard of care is revision arthroplasty to bypass the fracture and achieve stable diaphyseal fixation. A modular fluted tapered stem is highly successful in achieving diaphyseal fixation and restoring leg length and offset. ORIF alone is contraindicated for a loose stem.

Question 3506

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following conditions is considered an absolute contraindication to metal-on-metal hip resurfacing?

. Male gender
. Age greater than 50 years
. Osteoarthritis with large subchondral cysts
. Impaired renal function
. Avascular necrosis affecting 10% of the femoral head

Correct Answer & Explanation

. Impaired renal function

Explanation

Impaired renal function is an absolute contraindication to metal-on-metal (MoM) hip resurfacing or total hip arthroplasty. Metal ions (cobalt and chromium) generated by the articulation are primarily excreted by the kidneys. Renal insufficiency leads to toxic systemic accumulation of these ions. Female gender and large subchondral cysts are relative contraindications.

Question 3507

Topic: 3. Adult Reconstruction (Hip & Knee)

During the manufacturing of highly cross-linked polyethylene (HXLPE) for total hip arthroplasty, the material is subjected to gamma irradiation to induce cross-linking. Which of the following subsequent steps is most critical to eliminate free radicals and minimize the risk of in vivo oxidation?

. Annealing below the melting temperature
. Remelting above the melting temperature
. Sterilization using ethylene oxide
. Immersion in a saline bath
. Addition of titanium dioxide

Correct Answer & Explanation

. Remelting above the melting temperature

Explanation

Gamma irradiation creates free radicals that can lead to oxidation and subsequent mechanical degradation of the polyethylene. Remelting the polyethylene above its melting point allows the crystalline regions to melt, mobilizing and eliminating residual free radicals, thereby conferring high oxidation resistance. Annealing (heating below the melting point) leaves some residual free radicals.

Question 3508

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old female presents with isolated medial compartment knee osteoarthritis. She is evaluating options for a unicompartmental knee arthroplasty (UKA). Which of the following is considered an absolute contraindication to performing a UKA?

. Age less than 60 years
. Body Mass Index (BMI) greater than 30
. Inflammatory arthropathy
. Chondrocalcinosis without clinical inflammation
. A fixed varus deformity of 5 degrees

Correct Answer & Explanation

. Inflammatory arthropathy

Explanation

Inflammatory arthropathy (e.g., rheumatoid arthritis) is considered an absolute contraindication to unicompartmental knee arthroplasty due to the systemic, progressive nature of the disease affecting all compartments. Age, weight, and asymptomatic chondrocalcinosis are no longer considered absolute contraindications. A fixed varus deformity of <15 degrees can typically be corrected.

Question 3509

Topic: Total Knee Arthroplasty (TKA)

A 72-year-old male with a history of a total knee arthroplasty (TKA) 5 years ago presents with a chronic, massive rupture of the patellar tendon following a fall. He is unable to perform a straight leg raise. According to recent literature, which of the following reconstructive techniques demonstrates the best long-term survivorship and prevention of extensor lag?

. Direct primary repair using heavy non-absorbable sutures
. Augmentation with an autologous semitendinosus graft
. Extensor mechanism allograft with a tibial bone block
. Reconstruction using a synthetic mesh (e.g., Marlex)
. Gastrocnemius rotational flap without tendon reconstruction

Correct Answer & Explanation

. Reconstruction using a synthetic mesh (e.g., Marlex)

Explanation

For chronic, massive extensor mechanism disruptions post-TKA, direct repair has a prohibitively high failure rate. Recent literature heavily supports the use of synthetic mesh (such as Marlex mesh) reconstruction over allograft tissue, demonstrating superior long-term durability, fewer infections, and less late stretching (extensor lag).

Question 3510

Topic: Total Hip Arthroplasty (THA)

A 69-year-old female experiences recurrent posterior dislocations after a primary total hip arthroplasty performed through a posterior approach. Radiographic evaluation reveals the acetabular component is positioned in 30 degrees of abduction and 5 degrees of retroversion.

What is the most definitive surgical treatment to prevent future dislocations?

. Application of a hip abduction brace for 6 weeks
. Revision of the femoral head to a larger diameter
. Placement of a constrained acetabular liner
. Revision of the acetabular component to achieve proper anteversion and abduction
. Revision of the femoral stem to increase femoral offset

Correct Answer & Explanation

. Revision of the acetabular component to achieve proper anteversion and abduction

Explanation

The patient's acetabular component is severely malpositioned (retroverted and under-abducted). The 'safe zone' for cup placement is typically 40ยฑ10 degrees of abduction and 15ยฑ10 degrees of anteversion. While a larger head or constrained liner may add transient stability, they do not address the fundamental biomechanical failure and will likely result in impingement or early failure. The most definitive treatment is revising the malpositioned acetabular component.

Question 3511

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized (PS) total knee arthroplasty, gap assessment reveals a symmetric, well-balanced extension gap, but the flexion gap is unacceptably tight. Which of the following is the most appropriate technical step to resolve this imbalance?

. Release the posterior cruciate ligament (PCL)
. Release the posterior joint capsule
. Recut the distal femur to remove more bone
. Decrease the anteroposterior (AP) size of the femoral component
. Increase the thickness of the polyethylene insert

Correct Answer & Explanation

. Decrease the anteroposterior (AP) size of the femoral component

Explanation

A tight flexion gap with a balanced extension gap means the space in flexion must be increased without altering the extension gap. Decreasing the AP size of an anteriorly referenced femoral component decreases the posterior condylar offset, thereby increasing the flexion gap exclusively. Recutting the distal femur would affect only the extension gap. Increasing the poly thickness would tighten both gaps.

Question 3512

Topic: 3. Adult Reconstruction (Hip & Knee)
A 35-year-old male treated with high-dose corticosteroids for a systemic disease presents with right hip pain. Radiographs demonstrate an area of sclerosis with a visible subchondral radiolucent line (crescent sign), but no significant flattening of the femoral head. What is the most appropriate management for this hip?
. Core decompression
. Core decompression with non-vascularized fibular grafting
. Total hip arthroplasty
. Free vascularized fibular grafting
. Non-weight bearing and bisphosphonates

Correct Answer & Explanation

. Total hip arthroplasty

Explanation

The presence of a 'crescent sign' indicates subchondral fracture/collapse (Steinberg Stage III). Once subchondral collapse has occurred, joint-preserving procedures such as core decompression have unacceptably high failure rates. Total hip arthroplasty (THA) is the most reliable and appropriate treatment for symptomatic AVN with subchondral collapse, yielding the best functional outcomes even in younger patients.

Question 3513

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male undergoes a primary total knee arthroplasty. During intraoperative trialing, the knee is found to be tight in flexion but symmetric and well-balanced in extension. What is the most appropriate next step in management to address this gap imbalance?

. Recut the distal femur with more valgus
. Upsize the femoral component
. Increase the posterior slope of the tibial cut
. Downsize the tibial polyethylene insert
. Release the posterior capsule

Correct Answer & Explanation

. Increase the posterior slope of the tibial cut

Explanation

A knee that is tight in flexion and balanced in extension indicates a tight flexion gap. Ways to increase the flexion gap without affecting the extension gap include increasing the posterior slope of the tibial cut, downsizing the femoral component (to a smaller AP dimension, assuming anterior referencing), or translating the femoral component anteriorly. Downsizing the tibial insert would incorrectly increase both the flexion and extension gaps. Releasing the posterior capsule would primarily increase the extension gap.

Question 3514

Topic: Total Hip Arthroplasty (THA)

A 72-year-old woman presents with recurrent posterior dislocations following a primary total hip arthroplasty (THA) performed via a posterior approach. She has had three dislocations in the past 4 months. Radiographs demonstrate appropriate component positioning with an acetabular cup anteversion of 15 degrees and abduction of 40 degrees. The femoral stem is stable and in 15 degrees of anteversion. Which of the following is the most appropriate surgical option to minimize the risk of future dislocations?

. Revision of the acetabular component to increase anteversion to 30 degrees
. Revision of the femoral component to increase offset
. Placement of a constrained acetabular liner
. Conversion to a dual mobility bearing
. Anterior capsule release

Correct Answer & Explanation

. Conversion to a dual mobility bearing

Explanation

In the setting of recurrent posterior dislocation with well-positioned components and suspected soft tissue laxity or abductor deficiency, converting to a dual mobility bearing is a highly effective and reliable surgical option. Dual mobility bearings significantly increase the jump distance and the impingement-free range of motion. A constrained liner is another option but carries higher rates of wear and mechanical failure, and is typically reserved for severe abductor deficiency when dual mobility is contraindicated. Revising well-positioned components to abnormal versions is incorrect.

Question 3515

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with right knee pain 3 years after a total knee arthroplasty. Aspiration yields synovial fluid with a WBC count of 4,500 cells/uL with 85% PMNs. Serum CRP is 25 mg/L, and ESR is 40 mm/hr. Synovial fluid alpha-defensin testing is positive. According to the 2018 International Consensus Meeting (ICM) criteria, what is the correct diagnosis?

. Unlikely to have periprosthetic joint infection (PJI)
. Inconclusive for PJI
. Possible PJI
. Infected, meets major criteria for PJI
. Infected, meets minor criteria score for PJI

Correct Answer & Explanation

. Infected, meets minor criteria score for PJI

Explanation

Based on the 2018 ICM criteria for PJI, major criteria include two positive cultures or the presence of a sinus tract. Minor criteria utilize a scoring system: elevated CRP (>10 mg/L) or D-dimer (2 points), elevated ESR (>30 mm/hr) (1 point), elevated synovial WBC (>3000 cells/uL) or LE (3 points), positive alpha-defensin (3 points), elevated synovial PMN (>80%) (2 points). A score of >= 6 indicates an infection. This patient has: CRP (2) + ESR (1) + WBC (3) + PMN% (2) + alpha-defensin (3) = 11 points. Therefore, the patient is infected and meets the minor criteria score for PJI.

Question 3516

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man who underwent a metal-on-metal total hip arthroplasty 10 years ago presents with progressive groin pain and a palpable soft tissue mass. Serum cobalt and chromium levels are significantly elevated (Cobalt 15 ppb, Chromium 12 ppb). MARS MRI demonstrates a large, thick-walled cystic fluid collection compressing the femoral vein. What is the most appropriate management?

. Aspiration of the fluid collection under fluoroscopy
. Observation with serial MRIs and metal ion levels every 6 months
. Revision of the acetabular and femoral components to ceramic-on-polyethylene bearings
. Revision of the acetabular component and femoral head with thorough soft tissue debridement
. Administration of oral bisphosphonates and re-evaluation in 3 months

Correct Answer & Explanation

. Revision of the acetabular component and femoral head with thorough soft tissue debridement

Explanation

This patient has an Adverse Local Tissue Reaction (ALTR) or pseudotumor secondary to metal wear debris from a metal-on-metal THA. The presence of a symptomatic pseudotumor, elevated metal ions, and groin pain are absolute indications for revision surgery. The standard treatment is a revision of the bearing surfaces (acetabular cup and femoral head) to a non-metal-on-metal articulation (e.g., ceramic-on-polyethylene) accompanied by extensive debridement of the pseudotumor and necrotic tissues. A well-fixed femoral stem can typically be retained if the trunnion is intact.

Question 3517

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old woman who underwent a primary total knee arthroplasty 5 years ago presents with an inability to actively extend her knee following a mechanical fall. Radiographs demonstrate a high-riding patella (patella alta) with well-fixed TKA components. Clinical examination reveals a palpable defect inferior to the patella. What is the most appropriate surgical management for this condition?

. Primary end-to-end repair with non-absorbable sutures
. Primary repair augmented with cerclage wire
. Extensor mechanism allograft reconstruction
. Conversion to a hinged total knee arthroplasty
. Nonoperative management in an extension splint for 6 weeks

Correct Answer & Explanation

. Extensor mechanism allograft reconstruction

Explanation

The patient has sustained a complete patellar tendon rupture in the setting of a TKA (indicated by patella alta and inferior defect). Primary repair of a patellar tendon rupture after TKA has an unacceptably high failure rate due to poor tissue quality and compromised blood supply. Extensor mechanism reconstruction using a fresh-frozen full extensor mechanism allograft or Achilles tendon allograft with a bone block is the treatment of choice to restore active extension and optimize survivorship.

Question 3518

Topic: Total Hip Arthroplasty (THA)

A 62-year-old man undergoes primary total hip arthroplasty via a direct anterior approach. Intraoperatively, after placing the trial components, the leg lengths are perfectly equal compared to the contralateral side; however, the hip is unstable in extension and external rotation, tending to anteriorly dislocate. Which of the following component changes would most appropriately improve stability without increasing the patient's leg length?

. Increase the femoral head length
. Increase the femoral head size on the same neck length
. Change to a high-offset femoral stem
. Increase the anteversion of the acetabular cup
. Decrease the offset of the femoral stem

Correct Answer & Explanation

. Change to a high-offset femoral stem

Explanation

The hip is unstable in extension and external rotation, which characterizes anterior instability, a known risk of the direct anterior approach if there is insufficient tension in the anterior structures. Utilizing a high-offset femoral stem increases the global offset (lateralizing the femur), which increases the soft tissue tension of the abductors and short external rotators. This improves stability without lengthening the leg. Increasing the femoral head length would increase both offset and leg length.

Question 3519

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female with a severe 25-degree valgus deformity of the right knee undergoes a primary total knee arthroplasty via a lateral parapatellar approach. In the Post-Anesthesia Care Unit, she is unable to actively dorsiflex her right foot or extend her toes, and sensation is decreased over the dorsum of the foot. What is the most appropriate initial step in the management of this complication?

. Immediate surgical exploration and neurolysis of the peroneal nerve
. Removal of the surgical dressings and flexion of the knee to 20-30 degrees
. Application of an ankle-foot orthosis (AFO) and immediate full weight-bearing
. Closed manipulation of the knee under anesthesia
. Electromyography (EMG) and nerve conduction studies

Correct Answer & Explanation

. Removal of the surgical dressings and flexion of the knee to 20-30 degrees

Explanation

Peroneal nerve palsy is a severe complication following TKA for significant valgus deformities, often occurring due to traction or stretching of the nerve when the valgus alignment is acutely corrected to neutral. The immediate initial management includes removing all constrictive dressings and flexing the knee to 20-30 degrees to relieve tension on the peroneal nerve. Immediate surgical exploration is generally not indicated unless there is high suspicion of direct intraoperative transection or entrapment.

Question 3520

Topic: 3. Adult Reconstruction (Hip & Knee)

When comparing posterior-stabilized (PS) to cruciate-retaining (CR) total knee arthroplasty designs, which of the following kinematics or complications is most uniquely characteristic of a PS design?

. Paradoxical anterior sliding of the femur on the tibia during flexion
. Higher incidence of patellar clunk syndrome
. Increased dependence on the posterior cruciate ligament for femoral rollback
. Decreased incidence of wear at the modular tibial post
. Lower overall bone resection requirements from the intercondylar notch

Correct Answer & Explanation

. Higher incidence of patellar clunk syndrome

Explanation

Posterior-stabilized (PS) TKA designs replace the function of the PCL by utilizing a cam and post mechanism to enforce femoral rollback during flexion. This mechanism can lead to specific complications such as patellar clunk syndrome, which is caused by the formation of a fibrous nodule at the superior pole of the patella that catches within the intercondylar box during active extension. PS knees prevent paradoxical anterior sliding (which can occur in CR knees) and require more bone resection to accommodate the intercondylar box.

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