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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 166 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 3301

Topic: 3. Adult Reconstruction (Hip & Knee)

In evaluating a patient with persistent anterior thigh pain 1 year after receiving an uncemented total hip arthroplasty, radiographs reveal reactive cortical hypertrophy at the distal tip of the femoral stem. The porous-coated proximal region shows bone ingrowth without radiolucencies. What is the most likely diagnosis?

. Aseptic loosening of the femoral stem
. End-of-stem thigh pain due to a modulus mismatch
. Periprosthetic joint infection
. Subsidence of the femoral stem
. Polyethylene wear

Correct Answer & Explanation

. Aseptic loosening of the femoral stem

Explanation

End-of-stem pain occurs typically with stiff, well-fixed uncemented stems. It is a result of a modulus mismatch between the rigid metal implant and the more elastic diaphyseal bone, leading to stress transfer and reactive cortical thickening at the stem tip.

Question 3302

Topic: 3. Adult Reconstruction (Hip & Knee)

A 25-year-old male involved in a high-speed MVC sustains a type I Pipkin fracture-dislocation of the hip. Following closed reduction, a CT scan demonstrates a 1 cm displaced fracture fragment from the femoral head inferior to the fovea capitis, a concentrically reduced joint, and no intra-articular debris. What is the most appropriate management?

. Immediate spica casting
. Nonoperative management with protected weight bearing
. Open reduction and internal fixation
. Excision of the fragment
. Total hip arthroplasty

Correct Answer & Explanation

. Immediate spica casting

Explanation

Pipkin Type I fractures involve the femoral head inferior to the fovea (the non-weight bearing portion). If the hip joint is concentrically reduced and the fragment is small or does not mechanically block motion, nonoperative management with protected weight bearing is appropriate.

Question 3303

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior approach to the hip for a total hip arthroplasty, the surgeon releases the short external rotators. To minimize the risk of iatrogenic injury to the ascending branch of the medial femoral circumflex artery (MFCA), the surgeon should strictly protect the superior border of which of the following muscles?

. Obturator internus
. Quadratus femoris
. Piriformis
. Superior gemellus
. Gluteus maximus

Correct Answer & Explanation

. Obturator internus

Explanation

The main arterial supply to the femoral head comes from the deep branch of the MFCA. Its ascending branch crosses the posterior aspect of the hip joint capsule near the superior border of the quadratus femoris muscle, making it highly vulnerable during extensive posterior dissection.

Question 3304

Topic: 3. Adult Reconstruction (Hip & Knee)

A 67-year-old man is requesting revision surgery because of continued pain in the knee after undergoing a total knee replacement 2 years ago. Examination reveals that the knee is not warm, the incision is well-healed, and the skin has normal coloration and hair formation. No varus or valgus instability is noted, and knee range of motion is 5 degrees to 100 degrees. Laboratory studies show an erythrocyte sedimentation rate of 15 mm/h and a WBC of 5,000/mm3. Aspiration of the knee reveals clear fluid that shows no growth on culture. Radiographs reveal an appropriately positioned cruciate-retaining cemented total knee arthroplasty that is well-fixed. What is the probability that the patient's pain will be improved with revision surgery?

. 5%
. 10%
. 40%
. 60%
. 90%

Correct Answer & Explanation

. 5%

Explanation

The patient has a well-fixed and aligned painful total knee replacement. The success rate of revision knee replacement for pain when no mechanical problem can be identified is approximately 40%. The critical step is to rule out the presence of infection with appropriate laboratory studies and aspiration. If no infection is detected, revision should be avoided. Rand JA: Planning for revision total knee arthroplasty, in Zuckerman JD (ed): Instructional Course Lectures 48. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 161-166.

Question 3305

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 18 shows the radiograph of a patient with a total hip arthroplasty dislocation. During revision, increasing the diameter of the femoral head while maintaining the ratio of head-to-neck diameter constant has the effect of

. increasing the force to dislocation of the femoral head.
. increasing the range of motion until impingement of the neck on the liner.
. decreasing the resisting moment to dislocation of the femoral head.
. decreasing the range of motion until dislocation of the femoral head.
. decreasing the range of motion until impingement of the neck on the liner.

Correct Answer & Explanation

. increasing the force to dislocation of the femoral head.

Explanation

Although there is strong clinical and laboratory evidence that suggests smaller head size is linked with lower rates of polyethylene wear, moving to the use of 22-mm heads from larger sizes would tend to increase the dislocation rate. The key premise to this argument is that the absolute size of the femoral neck remains unchanged. While neck diameters were appropriate for the early monoblock femoral components, the use of modular femoral stems allows the surgeon to place 22-mm heads onto the same neck and trunion as used by larger heads. This has the effect of lessening the head-to-neck diameter ratio, which then accentuates the rate of impingement and dislocation. Reducing the neck diameter in proportion to the head diameter would eliminate the range-of-motion penalty accompanying head size reduction. Scifert and associates used a three-dimensional finite element model to study various combinations of femoral head size and neck ratios. They found that increasing the diameter of the femoral head while maintaining a constant head-to-neck diameter had the effect of significantly increasing the resisting moment necessary to induce a dislocation. The higher the head-to-neck ratio, the greater the range of motion until impingement and the greater the range of motion to dislocation.

Question 3306

Topic: 3. Adult Reconstruction (Hip & Knee)

During the insertion of acetabular screws for a cementless cup in a total hip arthroplasty, the surgeon divides the acetabulum into four quadrants based on a line drawn from the anterior superior iliac spine through the center of the acetabulum and an intersecting perpendicular line. Placement of screws in which quadrant places the external iliac artery and vein at the greatest risk of injury?

. Anterosuperior
. Anteroinferior
. Posterosuperior
. Posteroinferior
. Central

Correct Answer & Explanation

. Anterosuperior

Explanation

The anterosuperior quadrant places the external iliac vessels at high risk of iatrogenic injury. The posterosuperior and posteroinferior quadrants are considered the "safe zones" for screw placement.

Question 3307

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old woman presents to the emergency department after a mechanical fall. Radiographs reveal a periprosthetic femur fracture occurring around the tip of a cemented femoral stem. The stem is clinically and radiographically loose, but the proximal femoral bone stock remains intact and of good quality. According to the Vancouver classification, what is the most appropriate definitive management?

. Open reduction and internal fixation with locking plates and cerclage cables
. Open reduction and internal fixation with cortical strut allografts
. Revision arthroplasty using a standard-length cemented stem
. Revision arthroplasty using a long, distally fixing, porous-coated cementless stem
. Revision arthroplasty with proximal femoral replacement

Correct Answer & Explanation

. Open reduction and internal fixation with locking plates and cerclage cables

Explanation

This is a Vancouver B2 periprosthetic fracture, characterized by a fracture around a loose stem with adequate proximal bone stock. The standard of care is revision using a long, distally fixing cementless stem to bypass the fracture and provide stability.

Question 3308

Topic: 3. Adult Reconstruction (Hip & Knee)

In the pathogenesis of aseptic loosening secondary to polyethylene wear debris in total hip arthroplasty, which of the following is the primary cellular mediator responsible for initiating the inflammatory cascade that ultimately leads to osteolysis?

. Osteoblast
. Macrophage
. Neutrophil
. Lymphocyte
. Eosinophil

Correct Answer & Explanation

. Osteoblast

Explanation

Polyethylene wear particles are phagocytosed by macrophages, which then release inflammatory cytokines such as TNF-alpha, IL-1, and IL-6. This cascade stimulates osteoclastic bone resorption via the RANKL pathway, leading to osteolysis.

Question 3309

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old woman presents with progressive groin pain 5 years after receiving a large-head metal-on-metal total hip arthroplasty. MRI reveals a large, solid-cystic mass adjacent to the hip joint causing mass effect. Serum cobalt and chromium levels are significantly elevated. Infection has been ruled out. What is the most appropriate definitive management?

. Observation with serial MRIs
. Ultrasound-guided corticosteroid injection
. Revision arthroplasty to a ceramic-on-polyethylene bearing
. Long-term suppressive oral antibiotics
. Open debridement with component retention

Correct Answer & Explanation

. Observation with serial MRIs

Explanation

The patient is experiencing an adverse local tissue reaction (ALTR) or pseudotumor resulting from metal wear debris. Management requires surgical excision of the mass and revision of the bearing surfaces to a non-metal-on-metal articulation.

Question 3310

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the updated Musculoskeletal Infection Society (MSIS) and International Consensus Meeting (ICM) criteria, which of the following findings is considered a definitive major criterion for diagnosing a periprosthetic joint infection?

. Elevated erythrocyte sedimentation rate (ESR)
. Elevated serum C-reactive protein (CRP)
. Elevated synovial fluid white blood cell (WBC) count
. A sinus tract communicating with the prosthesis
. Positive leukocyte esterase strip test on synovial fluid

Correct Answer & Explanation

. Elevated erythrocyte sedimentation rate (ESR)

Explanation

The diagnosis of periprosthetic joint infection is definitively established by either of two major criteria: a sinus tract communicating with the prosthesis, or two positive periprosthetic cultures with phenotypically identical organisms. The other listed options are minor criteria.

Question 3311

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man who underwent a ceramic-on-ceramic total hip arthroplasty 2 years ago presents with a loud squeaking noise from his hip when walking and ascending stairs. He has no pain, and inflammatory markers are normal. Which of the following is the most significant risk factor for developing this phenomenon?

. Component malposition leading to edge loading
. Patient body mass index < 25 kg/m2
. Use of a highly cross-linked polyethylene liner
. Use of a 28-mm rather than a 36-mm femoral head
. Preoperative diagnosis of rheumatoid arthritis

Correct Answer & Explanation

. Component malposition leading to edge loading

Explanation

Squeaking in ceramic-on-ceramic bearings is strongly associated with component malposition, particularly severe cup anteversion or inclination, or extreme stem version. This malposition leads to stripe wear and edge loading, stripping the fluid lubrication layer from the bearing surface.

Question 3312

Topic: Total Hip Arthroplasty (THA)

A 60-year-old man experiences recurrent posterior dislocations after a total hip arthroplasty. Radiographs demonstrate a well-fixed stem and cup, but with significantly decreased femoral offset compared to the contralateral normal hip. Which of the following best describes the biomechanical consequence of increasing the femoral offset during revision surgery?

. Increases the abductor moment arm and soft tissue tension
. Decreases the abductor moment arm and increases joint reaction force
. Increases leg length without affecting abductor tension
. Decreases the risk of impingement by lateralizing the acetabulum
. Increases the stress on the femoral stem cement mantle exclusively

Correct Answer & Explanation

. Increases the abductor moment arm and soft tissue tension

Explanation

Increasing femoral offset lateralizes the femur, which increases the abductor moment arm and restores soft tissue tension. This improves joint stability and decreases the resultant joint reaction force. It typically does not significantly alter leg length.

Question 3313

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man undergoes a total hip arthroplasty using a ceramic-on-ceramic bearing. Two years later, he complains of an audible squeaking sound from the hip during walking. Which of the following acetabular component positions is most highly associated with this phenomenon?

. Acetabular anteversion of 15 degrees
. Acetabular inclination of 35 degrees
. Acetabular inclination of greater than 50 degrees
. Acetabular retroversion of 5 degrees
. Combined anteversion of 30 degrees

Correct Answer & Explanation

. Acetabular anteversion of 15 degrees

Explanation

Squeaking in ceramic-on-ceramic hips is strongly associated with edge loading, which disrupts the fluid lubrication film. This commonly occurs when the acetabular component is placed in excessive inclination (typically > 50 degrees). It leads to stripe wear on the ceramic head.

Question 3314

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following processes is primarily responsible for reducing wear and minimizing oxidation in modern highly cross-linked polyethylene used in total hip arthroplasty?

. Ethylene oxide sterilization followed by packaging in a vacuum
. Gamma irradiation followed by remelting or annealing
. Addition of vitamin E without irradiation
. Subsurface oxidation using hydrogen peroxide
. Increasing the thickness of the polyethylene liner above 8 mm

Correct Answer & Explanation

. Ethylene oxide sterilization followed by packaging in a vacuum

Explanation

Gamma irradiation generates free radicals that cross-link the polyethylene, which significantly reduces wear. Subsequent remelting or annealing extinguishes residual free radicals, minimizing the risk of oxidation and subsequent degradation over time.

Question 3315

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old woman with a history of recurrent posterior dislocations following a total hip arthroplasty presents for evaluation. Radiographs demonstrate well-fixed components with the acetabular cup at 40 degrees of abduction and 20 degrees of anteversion. Examination reveals a profound abductor lurch and a positive Trendelenburg sign. What is the most appropriate surgical intervention?

. Revision of the acetabular component to increase anteversion
. Advancement of the greater trochanter
. Revision to a dual-mobility articulation
. Exchange of the modular head to increase leg length
. Application of a knee-ankle-foot orthosis (KAFO)

Correct Answer & Explanation

. Revision of the acetabular component to increase anteversion

Explanation

Dual mobility components increase the effective head size and jump distance, greatly improving stability. They are the treatment of choice for recurrent instability associated with abductor deficiency when the existing components are well-positioned and fixed.

Question 3316

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old woman sustains a periprosthetic femur fracture around her cemented total hip arthroplasty after a fall.

Radiographs confirm a fracture at the tip of the stem. The stem appears loose, but the proximal bone stock is adequate (Vancouver Type B2). What is the recommended surgical management?

. Open reduction and internal fixation with locking plates and cerclage cables
. Revision to a standard-length cemented stem
. Revision to a long uncemented diaphyseal-engaging stem
. Impaction bone grafting with a shorter cemented stem
. Resection arthroplasty (Girdlestone procedure)

Correct Answer & Explanation

. Open reduction and internal fixation with locking plates and cerclage cables

Explanation

A Vancouver B2 fracture is characterized by a loose stem in the presence of adequate proximal bone stock. The standard of care is revision arthroplasty bypassing the fracture site with a long, uncemented, distally fixing stem.

Question 3317

Topic: 3. Adult Reconstruction (Hip & Knee)

During preoperative templating for a total hip arthroplasty utilizing a standard femoral stem with a neck-shaft angle of 135 degrees, the surgeon decides to increase the modular neck length by 4 mm. How will this change affect the patient's leg length and femoral offset?

. Increase leg length by 4 mm with no change in offset
. Increase offset by 4 mm with no change in leg length
. Increase leg length and offset in approximately a 1:1 ratio
. Increase leg length and offset in approximately a 2:1 ratio
. Decrease leg length by 2 mm and increase offset by 4 mm

Correct Answer & Explanation

. Increase leg length by 4 mm with no change in offset

Explanation

For a standard neck angle of 135 degrees, the trigonometric relationship (sine and cosine of 45 degrees) dictates that increasing the neck length changes the offset and leg length equally. Therefore, they increase in a 1:1 ratio.

Question 3318

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man presents with groin pain and a palpable anterior mass 4 years after receiving a metal-on-metal total hip arthroplasty. Aspiration yields sterile, turbid fluid. What is the classic histologic hallmark found in the periprosthetic tissue?

. Extensive neutrophilic infiltrate with bacteria
. Perivascular lymphocytic infiltrate
. Abundant multinucleated foreign body giant cells with birefringent particles
. Monosodium urate crystals
. Fibrocartilaginous metaplasia of the synovium

Correct Answer & Explanation

. Extensive neutrophilic infiltrate with bacteria

Explanation

Adverse local tissue reactions (ALTR) associated with metal-on-metal implants are characterized by Aseptic Lymphocytic Vasculitis-Associated Lesions (ALVAL). The defining histologic feature is a dense perivascular lymphocytic infiltrate.

Question 3319

Topic: 3. Adult Reconstruction (Hip & Knee)

A 40-year-old woman with systemic lupus erythematosus on chronic corticosteroids presents with severe left hip pain. Radiographs reveal a subchondral lucent line (crescent sign) with flattening of the femoral head. What is the most appropriate definitive surgical treatment?

. Core decompression
. Non-vascularized fibular strut grafting
. Vascularized free fibular grafting
. Total hip arthroplasty
. Pemberton osteotomy

Correct Answer & Explanation

. Core decompression

Explanation

The crescent sign indicates subchondral fracture and collapse, marking a transition to Ficat Stage III avascular necrosis. Once collapse has occurred, joint-preserving procedures like core decompression are ineffective, and total hip arthroplasty is indicated.

Question 3320

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with a painful total hip arthroplasty 3 years postoperatively. Serum ESR and CRP are normal, but clinical suspicion for chronic periprosthetic joint infection (PJI) remains high. Which of the following synovial fluid biomarkers offers the highest specificity for diagnosing PJI?

. Interleukin-6
. Lactate dehydrogenase
. Alpha-defensin
. C-reactive protein
. Glucose

Correct Answer & Explanation

. Interleukin-6

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. It maintains high sensitivity and specificity for diagnosing periprosthetic joint infections, even when traditional serum inflammatory markers are equivocal or normal.

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