Menu

3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 280 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 5581

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old male sustains a periprosthetic femur fracture following a mechanical fall, 10 years after a primary THA. Radiographs demonstrate a fracture strictly around the tip of the femoral stem. The stem is visibly subsided and loose on radiographs, but there is excellent, intact bone stock in the proximal femur. According to the Vancouver classification, what is the fracture type and the recommended treatment?

. Vancouver B1; Open reduction and internal fixation with a locking plate and cables.
. Vancouver B2; Revision to a long cementless fully porous-coated or fluted tapered stem.
. Vancouver B3; Revision with a proximal femoral replacement.
. Vancouver C; Open reduction and internal fixation alone.
. Vancouver A; Non-operative management with protected weight-bearing.

Correct Answer & Explanation

. Vancouver B1; Open reduction and internal fixation with a locking plate and cables.

Explanation

The Vancouver classification dictates treatment for periprosthetic femoral fractures. Type A is trochanteric. Type B is around the stem. Type C is well below the stem. Within Type B: B1 fractures have a well-fixed stem (treated with ORIF). B2 fractures have a loose stem but adequate proximal bone stock (treated with revision to a longer cementless stem that bypasses the fracture by at least two cortical diameters). B3 fractures have a loose stem and poor proximal bone stock (treated with proximal femoral replacement or complex reconstruction).

Question 5582

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male with a metal-on-polyethylene THA presents with a large soft tissue mass in the groin and local discomfort. Joint aspiration reveals cloudy fluid with a WBC count of 1,200 cells/uL, 40% neutrophils, and negative bacterial cultures. Blood tests demonstrate an elevated serum cobalt level but a normal chromium level. What is the most likely etiology of this presentation?

. Unrecognized low-grade periprosthetic joint infection.
. Polyethylene wear-induced osteolysis.
. Trunnionosis at the modular head-neck junction.
. Adverse local tissue reaction secondary to cup malposition.
. Hypersensitivity to the titanium femoral stem.

Correct Answer & Explanation

. Unrecognized low-grade periprosthetic joint infection.

Explanation

The presentation is classic for an Adverse Local Tissue Reaction (ALTR) secondary to trunnionosis (mechanically assisted crevice corrosion) at the modular head-neck taper. In a metal-on-polyethylene bearing, the most common source of metal ions is the trunnion (typically a cobalt-chromium head on a titanium stem). This produces a characteristic discordant elevation of serum cobalt over chromium (unlike metal-on-metal bearing wear, where both are elevated). The low WBC count and negative cultures rule out PJI.

Question 5583

Topic: Total Hip Arthroplasty (THA)

During a primary THA, the surgeon considers options for the modular femoral head. Increasing the femoral neck length without changing the neck-shaft angle of the stem will have which of the following biomechanical effects?

. Decreases femoral offset and decreases leg length.
. Increases femoral offset and increases leg length.
. Increases femoral offset and decreases leg length.
. Decreases femoral offset and increases leg length.
. Increases leg length without affecting femoral offset.

Correct Answer & Explanation

. Decreases femoral offset and decreases leg length.

Explanation

The femoral neck acts as a vector extending superomedially from the shaft. Because the neck sits at an angle (the neck-shaft angle, typically ~135 degrees), adding length along this axis moves the center of rotation both proximally (increasing vertical leg length) and medially relative to the femur, which functionally pushes the femur laterally relative to the pelvis (increasing horizontal femoral offset). Therefore, increasing neck length increases both leg length and femoral offset.

Question 5584

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following factors is most strongly associated with the phenomenon of 'squeaking' in a patient with a Ceramic-on-Ceramic (CoC) total hip arthroplasty?

. The use of a standard 28mm diameter femoral head.
. A history of prior periprosthetic joint infection.
. Malpositioning of the acetabular component leading to edge loading.
. Use of a highly polished cemented femoral stem.
. Low patient body mass index (BMI < 20).

Correct Answer & Explanation

. The use of a standard 28mm diameter femoral head.

Explanation

Squeaking is a well-documented complication of Ceramic-on-Ceramic bearings. It is most strongly correlated with component malposition (such as excessive cup inclination or retroversion/anteversion mismatch), which causes 'edge loading.' Edge loading results in stripe wear on the ceramic head, loss of fluid film lubrication, and generation of acoustic vibrations (squeaking). Patient factors (like high BMI, young age) and implant factors (like short stems) can contribute, but mechanical edge loading is the primary pathophysiologic mechanism.

Question 5585

Topic: 3. Adult Reconstruction (Hip & Knee)
A 28-year-old female on chronic corticosteroids for systemic lupus erythematosus presents with severe right hip pain. Radiographs demonstrate a subchondral radiolucent line (crescent sign) with mild flattening of the femoral head, but the joint space remains fully preserved. According to the Ficat and Arlet classification, what is the stage and the most reliable definitive surgical treatment for her pain?
. Stage II; Core decompression and bone grafting.
. Stage III; Core decompression.
. Stage III; Total hip arthroplasty.
. Stage IV; Arthroscopic debridement.
. Stage I; Total hip arthroplasty.

Correct Answer & Explanation

. Stage III; Total hip arthroplasty.

Explanation

The subchondral crescent sign indicates subchondral fracture/collapse, which corresponds to Ficat and Arlet Stage III avascular necrosis (AVN). The joint space is preserved in Stage III, whereas Stage IV involves joint space narrowing and secondary osteoarthritis. Once structural collapse has occurred (Stage III), joint-preserving procedures such as core decompression have a high failure rate. Total hip arthroplasty is the most reliable definitive treatment to relieve pain and restore function in this setting.

Question 5586

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old male is 3 weeks postoperative from a primary THA. He presents to the emergency department with a 2-day history of acute severe hip pain, erythema, and purulent drainage from the distal aspect of the surgical incision. He is hemodynamically stable. Joint aspiration yields 75,000 WBCs/ยตL with 95% neutrophils. Radiographs show a well-fixed implant without evidence of loosening. What is the most appropriate surgical management?

. Debridement, antibiotics, and implant retention (DAIR) with exchange of modular components.
. Single-stage revision arthroplasty.
. Two-stage revision arthroplasty with an articulating antibiotic spacer.
. Intravenous antibiotics alone for 6 weeks followed by indefinite oral suppression.
. Immediate superficial incision and drainage in the emergency department.

Correct Answer & Explanation

. Debridement, antibiotics, and implant retention (DAIR) with exchange of modular components.

Explanation

The patient has an acute post-operative periprosthetic joint infection (PJI) occurring within 4 weeks of the index surgery, with a well-fixed implant and a relatively short duration of symptoms (2 days). This scenario is the classical indication for Debridement, Antibiotics, and Implant Retention (DAIR), accompanied by the exchange of modular components (the polyethylene liner and femoral head) to access the joint space completely and remove biofilm on modular interfaces. Superficial I&D without joint exploration in a suspected deep PJI is contraindicated.

Question 5587

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following patients is at the highest risk for developing clinically significant heterotopic ossification (HO) following a primary total hip arthroplasty, and would most clearly benefit from prophylactic radiation or NSAID therapy?

. A 60-year-old female with primary osteoarthritis and osteoporosis.
. A 55-year-old male undergoing THA for severe ankylosing spondylitis.
. A 70-year-old female undergoing THA for a displaced femoral neck fracture.
. A 65-year-old male with avascular necrosis of the femoral head secondary to alcohol abuse.
. A 50-year-old female with long-standing rheumatoid arthritis.

Correct Answer & Explanation

. A 60-year-old female with primary osteoarthritis and osteoporosis.

Explanation

High-risk factors for heterotopic ossification (HO) following THA include ankylosing spondylitis, hypertrophic osteoarthritis, diffuse idiopathic skeletal hyperostosis (DISH), a history of prior HO, post-traumatic arthritis, and male gender. Rheumatoid arthritis is actually considered a low-risk condition for HO. Given the systemic ossifying nature of ankylosing spondylitis, this patient is at very high risk and warrants prophylaxis with either single-dose low-dose radiation or a postoperative NSAID regimen (e.g., indomethacin).

Question 5588

Topic: 3. Adult Reconstruction (Hip & Knee)

In the setting of a revision total hip arthroplasty with significant femoral bone loss, impaction bone grafting is a technique used to restore host bone stock. According to established principles, this technique is most successful when applied to which type of bone defect, and matched with which specific type of femoral stem?

. Segmental bone loss; a fully porous-coated cylindrical cementless stem.
. Cavitary bone loss with an intact cortical tube; a highly polished, collarless, tapered cemented stem.
. Segmental bone loss; a modular fluted tapered cementless stem.
. Cavitary bone loss; a proximally porous-coated cementless stem.
. Complete cortical perforation; a fully hydroxyapatite-coated cementless stem.

Correct Answer & Explanation

. Segmental bone loss; a fully porous-coated cylindrical cementless stem.

Explanation

Impaction bone grafting involves tightly packing cancellous allograft into a contained femoral defect, followed by cementing a stem into the graft. For the graft to consolidate and remodel, it requires mechanical loading (Wolff's law) and containment. Therefore, it is indicated for contained (cavitary) defects with an intact cortical tube. A highly polished, collarless, tapered stem (such as the Exeter stem) is required because it allows controlled subsidence, continually wedging into the cement mantle and providing continuous radial compressive forces to the bone graft.

Question 5589

Topic: 3. Adult Reconstruction (Hip & Knee)

Which histological finding is the distinct hallmark of Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion (ALVAL), commonly seen in failed metal-on-metal total hip arthroplasties?

. Dense fibrovascular tissue with foreign body giant cells containing birefringent polyethylene debris.
. Extensive polymorphonuclear leukocyte infiltration indicative of acute inflammation.
. Mononuclear macrophages with massive intracellular ceramic particles.
. Perivascular lymphocytic cuffing, extensive necrosis, and fibrin exudation.
. Fungal hyphae and non-caseating granuloma formation.

Correct Answer & Explanation

. Dense fibrovascular tissue with foreign body giant cells containing birefringent polyethylene debris.

Explanation

ALVAL (Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion) represents a delayed Type IV hypersensitivity reaction to metal ions (cobalt and chromium). The classic histological hallmarks of ALVAL are heavy perivascular lymphocytic infiltrates (cuffing), a massive localized accumulation of lymphocytes, and large areas of tissue necrosis and fibrin exudation. Option A describes the typical response to polyethylene wear, and Option B describes an acute bacterial infection.

Question 5590

Topic: 3. Adult Reconstruction (Hip & Knee)

In the setting of a complex revision total hip arthroplasty, the surgeon suspects a pelvic discontinuity. Which of the following defines the pathognomonic radiographic/anatomic criterion for pelvic discontinuity?

. Superior migration of the acetabular component greater than 3 cm above the obturator line.
. Medial migration of the acetabular component completely past Kohler's line.
. A transverse separation of the superior hemipelvis from the inferior hemipelvis.
. Complete osteolysis of the ischium and the radiographic teardrop.
. Obturator ring asymmetry greater than 1 cm compared to the contralateral side.

Correct Answer & Explanation

. Superior migration of the acetabular component greater than 3 cm above the obturator line.

Explanation

Pelvic discontinuity is defined mechanically and radiographically as a complete transverse separation between the superior hemipelvis (ilium) and the inferior hemipelvis (ischium/pubis) through the acetabulum. This essentially breaks the pelvis into two separate segments, rendering standard hemispherical acetabular cups useless unless structural stability between the two halves is restored (e.g., using a cup-cage construct, custom triflange, or distraction techniques). Medial and superior migration describe severe bone loss (e.g., Paprosky 3B) but do not inherently define discontinuity.

Question 5591

Topic: Total Hip Arthroplasty (THA)

A 72-year-old female presents to the emergency room with a posterior dislocation of her THA. The index surgery was performed 4 weeks ago via a posterior approach. She states she dropped a pen and bent over deeply at the waist to pick it up. A successful closed reduction is performed in the ER. Post-reduction radiographs confirm the cup is positioned at 40 degrees of inclination and 20 degrees of anteversion. What is the most appropriate next step in management?

. Immediate revision to a constrained acetabular liner.
. Immediate revision to a dual-mobility construct.
. Application of an abduction brace for 6 to 12 weeks and strict reinforcement of hip precautions.
. Open reduction and primary repair of the posterior capsular soft tissues.
. Surgical exchange of the femoral head to a longer neck length.

Correct Answer & Explanation

. Immediate revision to a constrained acetabular liner.

Explanation

This is a first-time dislocation occurring early in the postoperative period (< 6 weeks) resulting from an obvious provocative maneuver (extreme flexion/internal rotation). The acetabular component is well-positioned in the safe zone (40ยฐ inclination, 20ยฐ anteversion). The standard of care for an initial, early, position-provoked dislocation with well-oriented components is conservative management. This typically includes closed reduction, application of a hip abduction brace for 6-12 weeks to allow capsular healing, and strict adherence to hip precautions.

Question 5592

Topic: Total Hip Arthroplasty (THA)

Intraoperatively during a primary THA using trial components, the surgeon performs a 'shuck' test (longitudinal traction) and notes excessive joint laxity of 8 mm. However, when the legs are placed parallel in full extension, clinical assessment clearly indicates that the operative leg is already 1.5 cm longer than the contralateral leg. The components are stable in extreme range of motion without impingement. To restore soft tissue tension without further exacerbating the leg length discrepancy, what is the optimal surgical adjustment?

. Increase the neck length of the femoral head trial.
. Decrease the neck length of the femoral head and increase cup anteversion.
. Utilize a femoral stem with increased horizontal offset.
. Advance the femoral stem deeper into the medullary canal.
. Deepen the acetabulum by reaming medially.

Correct Answer & Explanation

. Increase the neck length of the femoral head trial.

Explanation

The patient has insufficient soft tissue tension (laxity/positive shuck) but is already significantly lengthened relative to the contralateral side. Increasing the neck length will appropriately tighten the joint but will unacceptably increase the leg length further. The solution to tighten the abductor mechanism and joint capsule without adding vertical length is to increase the horizontal offset. This can be achieved by using a high-offset femoral stem or lateralized acetabular liner.

Question 5593

Topic: Total Hip Arthroplasty (THA)

A 54-year-old male with end-stage hip osteoarthritis has a concomitant 2.5 cm leg length discrepancy (the operative leg is shorter). During THA, the surgeon lengthens the leg by 2.5 cm to restore symmetry. Postoperatively, the patient develops a foot drop and parasthesias in the lateral lower leg. Electromyography (EMG) performed 4 weeks later would most likely demonstrate which finding if a stretch injury to the sciatic nerve occurred?

. Fibrillation potentials strictly in the medial head of the gastrocnemius.
. Denervation potentials in the short head of the biceps femoris and tibialis anterior.
. Normal motor unit action potentials in the extensor hallucis longus.
. Fibrillation potentials in the quadriceps femoris.
. Denervation strictly in the adductor longus and brevis.

Correct Answer & Explanation

. Fibrillation potentials strictly in the medial head of the gastrocnemius.

Explanation

A stretch injury from excessive lengthening (>2-3 cm) most commonly affects the common peroneal division of the sciatic nerve. The short head of the biceps femoris is the only muscle innervated by the common peroneal division of the sciatic nerve above the knee. The tibialis anterior is innervated by the deep peroneal nerve (a continuation of the common peroneal nerve). Fibrillation and denervation potentials in both these muscles confirm a high common peroneal nerve lesion at the level of the sciatic nerve (the hip), distinguishing it from a local peroneal palsy at the fibular head (which would spare the short head of the biceps femoris).

Question 5594

Topic: Total Hip Arthroplasty (THA)

In total hip arthroplasty (THA), utilizing the posterior approach carries a higher risk of postoperative dislocation compared to the direct anterior approach. Which of the following anatomical structures is primarily repaired to mitigate this risk?

. Gluteus medius and minimus
. Piriformis, superior gemellus, obturator internus, inferior gemellus
. Obturator externus and quadratus femoris
. Iliopsoas tendon
. Tensor fasciae latae

Correct Answer & Explanation

. Gluteus medius and minimus

Explanation

The posterior approach to the hip involves releasing the short external rotators (piriformis, superior gemellus, obturator internus, inferior gemellus) and the posterior capsule. An enhanced posterior soft tissue repair, which involves suturing these structures back to the greater trochanter, significantly reduces the postoperative dislocation rate.

Question 5595

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, after making the standard bone cuts, the surgeon notices that the knee is tight in flexion but symmetric and well-balanced in extension. Which of the following adjustments is most appropriate to balance the knee?

. Resect more distal femur
. Increase the posterior slope of the tibial cut
. Downsize the femoral component and use a thicker polyethylene insert
. Release the posterior capsule
. Upsize the femoral component

Correct Answer & Explanation

. Resect more distal femur

Explanation

A knee that is tight in flexion but balanced in extension has an isolated tight flexion gap. Interventions to increase the flexion gap without altering the extension gap include increasing the posterior slope of the tibial cut or downsizing the femoral component (which decreases the AP dimension). Option 1 directly addresses the tight flexion gap. Option 3 is incorrect because using a thicker insert would tighten the extension gap.

Question 5596

Topic: 3. Adult Reconstruction (Hip & Knee)

During total hip arthroplasty, increasing the femoral offset without changing the leg length will have which of the following biomechanical effects?

. Increase the force required by the abductors
. Increase the joint reactive force
. Decrease the tension on the abductors
. Increase the risk of bony impingement
. Decrease the mechanical advantage of the abductors

Correct Answer & Explanation

. Increase the force required by the abductors

Explanation

Increasing femoral offset moves the femur further from the center of rotation, increasing the moment arm (mechanical advantage) of the abductor muscles. This decreases the force required by the abductors to maintain a level pelvis, thus decreasing the joint reactive force.

Question 5597

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following bearing surface combinations in total hip arthroplasty demonstrates the lowest linear and volumetric wear rates in laboratory simulator studies?

. Cobalt-chromium on highly cross-linked polyethylene
. Ceramic on highly cross-linked polyethylene
. Cobalt-chromium on conventional polyethylene
. Ceramic on ceramic
. Metal on metal

Correct Answer & Explanation

. Cobalt-chromium on highly cross-linked polyethylene

Explanation

Ceramic-on-ceramic bearing surfaces have the lowest linear and volumetric wear rates of all combinations due to high hardness, scratch resistance, and excellent wettability. However, they carry specific risks, such as squeaking and catastrophic brittle fracture.

Question 5598

Topic: 3. Adult Reconstruction (Hip & Knee)

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

. Elevated serum CRP and ESR
. Elevated synovial fluid white blood cell count
. Purulence in the affected joint
. A sinus tract communicating with the prosthesis
. Positive histological analysis of periprosthetic tissue

Correct Answer & Explanation

. Elevated serum CRP and ESR

Explanation

The major criteria for definitive periprosthetic joint infection (PJI) are: 1) Two positive periprosthetic cultures with phenotypically identical organisms, or 2) A sinus tract communicating with the joint. The other options are considered minor criteria.

Question 5599

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, which bearing surface combination is uniquely associated with the phenomenon of 'stripe wear' and potential squeaking?

. Cobalt-chrome on highly cross-linked polyethylene
. Ceramic on ceramic
. Ceramic on highly cross-linked polyethylene
. Cobalt-chrome on cobalt-chrome
. Oxidized zirconium on conventional polyethylene

Correct Answer & Explanation

. Cobalt-chrome on highly cross-linked polyethylene

Explanation

Ceramic-on-ceramic (CoC) bearings have excellent overall wear properties but are associated with specific complications, including squeaking and 'stripe wear'. Stripe wear occurs due to edge loading or microseparation during the swing phase, where the femoral head contacts the edge of the ceramic liner, leaving a narrow track of wear.

Question 5600

Topic: 3. Adult Reconstruction (Hip & Knee)

During normal native knee flexion, the femoral condyles exhibit posterior rollback. In a posterior-stabilized (PS) total knee arthroplasty, which of the following mechanical features substitutes for the posterior cruciate ligament (PCL) to induce this posterior rollback?

. The highly congruent deep-dish polyethylene insert
. The interaction between the femoral cam and the tibial post
. The retained tension of the medial collateral ligament
. The built-in anterior slope of the tibial tray
. The symmetric multiradius design of the femoral condyles

Correct Answer & Explanation

. The highly congruent deep-dish polyethylene insert

Explanation

In a posterior-stabilized (PS) total knee arthroplasty, the PCL is excised. Posterior femoral rollback during flexion is achieved mechanically by the engagement of the femoral cam against the tibial polyethylene post. This prevents anterior translation of the femur on the tibia during deep flexion, mimicking the function of the native PCL.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page