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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 267 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 5321

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female with a history of recurrent total hip arthroplasty (THA) dislocations and severe abductor deficiency undergoes revision THA with the placement of a constrained acetabular liner. Which of the following is the most significant long-term complication associated specifically with the use of a constrained liner in this setting?

. Aseptic loosening of the acetabular component
. Accelerated wear of the femoral head
. Sciatic nerve palsy
. Trunnionosis at the head-neck junction
. Spontaneous pelvic dissociation

Correct Answer & Explanation

. Aseptic loosening of the acetabular component

Explanation

Constrained liners are used in patients with severe abductor deficiency or recurrent instability where other options (like dual mobility) are insufficient. Because the femoral head is locked into the liner, impingement or extreme ranges of motion transmit significant torque and shear forces directly to the liner-cup and cup-bone interfaces. This drastically increases the risk of aseptic loosening and mechanical failure of the acetabular component.

Question 5322

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with new-onset right groin pain 8 years after a primary THA. He has a metal-on-polyethylene bearing with a large-diameter (36-mm) cobalt-chromium femoral head on a titanium stem. Radiographs show a well-fixed prosthesis with no osteolysis. Serum cobalt levels are significantly elevated, while chromium levels are normal. MRI demonstrates a solid and cystic soft-tissue mass around the hip joint. What is the most likely diagnosis?

. Polyethylene wear-induced osteolysis
. Periprosthetic joint infection
. Trunnionosis (mechanically assisted crevice corrosion)
. Iliopsoas impingement
. Adverse local tissue reaction due to bearing surface wear

Correct Answer & Explanation

. Polyethylene wear-induced osteolysis

Explanation

Trunnionosis, or mechanically assisted crevice corrosion, occurs at the modular head-neck junction. It is particularly associated with large-diameter metal heads on titanium stems (which increase the torsional forces at the trunnion). The classic serological profile is a preferential elevation of cobalt over chromium. This leads to an adverse local tissue reaction (ALTR) or ALVAL, presenting as a pseudotumor despite a metal-on-polyethylene bearing.

Question 5323

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following synovial fluid biomarkers utilized in the diagnosis of periprosthetic joint infection (PJI) is an antimicrobial peptide naturally produced by neutrophils?

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

Correct Answer & Explanation

. Interleukin-6 (IL-6)

Explanation

Alpha-defensin is an antimicrobial peptide secreted by neutrophils in response to pathogens. It is a highly sensitive and specific synovial fluid biomarker for diagnosing PJI. Leukocyte esterase is an enzyme produced by neutrophils, not an antimicrobial peptide itself. CRP, IL-6, and D-dimer are acute-phase reactants or systemic markers.

Question 5324

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty (TKA), after the initial bone cuts are made, the surgeon evaluates the gaps using spacer blocks. The flexion gap is perfectly balanced and symmetric, but the extension gap is excessively tight. Which of the following is the most appropriate next step to achieve balance?

. Release the posterior capsule and/or resect more distal femur
. Downsize the femoral component
. Resect more proximal tibia
. Upsize the femoral component
. Release the superficial medial collateral ligament

Correct Answer & Explanation

. Release the posterior capsule and/or resect more distal femur

Explanation

A knee that is balanced in flexion but tight in extension requires an intervention that only affects the extension gap. Resecting more distal femur or releasing the posterior capsule will increase the extension gap without significantly altering the flexion gap. Resecting more proximal tibia would increase both gaps symmetrically. Downsizing the femur increases the flexion gap.

Question 5325

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old female presents with an inability to perform a straight leg raise 6 months after a primary TKA. Ultrasound confirms a complete, retracted rupture of the patellar tendon. The primary TKA components are well-fixed. What is the most reliable surgical option for restoring function in this chronic setting?

. Primary end-to-end repair with non-absorbable sutures
. Primary repair augmented with cerclage wiring
. Extensor mechanism allograft reconstruction
. Revision to a rotating hinge knee arthroplasty
. Patellectomy and V-Y quadricepsplasty

Correct Answer & Explanation

. Primary end-to-end repair with non-absorbable sutures

Explanation

Chronic patellar tendon ruptures following TKA are notoriously difficult to treat due to poor tissue quality and retraction. Primary repair (with or without wire augmentation) has a high failure rate in the chronic setting. Reconstruction using an extensor mechanism allograft (often comprising the tibial tubercle, patellar tendon, patella, and quadriceps tendon) or synthetic mesh is the gold standard for restoring the extensor mechanism in a chronic post-TKA disruption.

Question 5326

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female presents with chronic pelvic pain 15 years after a revision THA.

Radiographs demonstrate severe osteolysis, medial migration of the acetabular component, and a complete fracture line extending through Kohler's line, separating the superior and inferior hemipelvis. What is the most definitive intraoperative finding that confirms pelvic discontinuity, and what is the optimal reconstructive strategy?

. Independent movement of the superior and inferior hemipelvis; Reconstruction with a standard hemispherical porous cup
. Intact posterior column; Reconstruction with an impaction bone grafting technique
. Independent movement of the superior and inferior hemipelvis; Reconstruction with a cup-cage construct or custom triflange
. Absence of the anterior column; Reconstruction with a bipolar hemiarthroplasty
. Aseptic loosening of the cup; Reconstruction with an anti-protrusio cage alone

Correct Answer & Explanation

. Independent movement of the superior and inferior hemipelvis; Reconstruction with a standard hemispherical porous cup

Explanation

Pelvic discontinuity is defined by a complete separation of the superior (ilium) and inferior (ischium/pubis) hemipelvis. The definitive intraoperative diagnosis is independent mobility between the two halves. Reconstruction requires bypassing the defect and stabilizing both halves, typically utilizing a highly porous jumbo cup with distraction, a cup-cage construct, or a custom triflange acetabular component. Standard cups or cages alone lack the biological fixation and mechanical stability required to heal the discontinuity.

Question 5327

Topic: 3. Adult Reconstruction (Hip & Knee)

Based on the classic Kozinn and Scott criteria, which of the following is considered an absolute contraindication to a unicompartmental knee arthroplasty (UKA) for anteromedial osteoarthritis?

. Age older than 60 years
. Weight greater than 82 kg
. Inflammatory arthropathy
. Patellofemoral joint osteophytes without full-thickness cartilage loss
. Chondrocalcinosis of the menisci

Correct Answer & Explanation

. Age older than 60 years

Explanation

Inflammatory arthropathy (e.g., rheumatoid arthritis) is an absolute contraindication to UKA due to the systemic, pan-articular nature of the disease, which will predictably destroy the preserved compartments. While Kozinn and Scott originally proposed weight >82 kg and age <60 as contraindications, these are now considered relative or obsolete. Asymptomatic patellofemoral osteophytes or chondrocalcinosis without frank arthritis are not absolute contraindications.

Question 5328

Topic: 3. Adult Reconstruction (Hip & Knee)

In the biomechanical design of a dual-mobility acetabular component for THA, which of the following principles best explains its enhanced stability compared to a standard fixed-liner THA?

. Decreased jump distance of the primary articulation
. Increased effective femoral head size provided by the mobile polyethylene liner
. Reduction in total range of motion before component impingement
. Increased friction at the inner bearing surface
. Utilization of a constrained locking mechanism

Correct Answer & Explanation

. Decreased jump distance of the primary articulation

Explanation

Dual-mobility components consist of a small inner metal or ceramic head that articulates within a larger mobile polyethylene liner, which in turn articulates within the metal acetabular shell. The stability is primarily conferred by the large effective outer diameter of the mobile polyethylene head, which dramatically increases the 'jump distance' (the distance the head must translate to dislocate) and allows for a greater impingement-free range of motion.

Question 5329

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old female sustains a periprosthetic femur fracture around her THA.

Radiographs show the fracture involves the bone around the stem, the stem is definitively loose, and there is severe comminution and osteolysis of the proximal femur leaving entirely inadequate bone stock for proximal fixation. According to the Vancouver classification, what is the most appropriate management?

. Open reduction and internal fixation with a lateral locking plate and cerclage cables
. Revision THA using a standard primary cementless stem
. Revision THA utilizing a long fluted tapered modular stem achieving distal fixation, or a proximal femoral replacement
. Nonoperative management with a spica cast
. Cement-in-cement revision using a short stem

Correct Answer & Explanation

. Open reduction and internal fixation with a lateral locking plate and cerclage cables

Explanation

This is a Vancouver B3 fracture: the fracture is around the stem (B), the stem is loose (3), and the proximal bone stock is inadequate (3). Treatment requires bypassing the deficient proximal bone to achieve stable fixation in the intact distal diaphysis using a long, distally fixing fluted tapered modular stem (often with structural allograft) or, in older/sedentary patients, a proximal femoral replacement (tumor prosthesis).

Question 5330

Topic: Total Hip Arthroplasty (THA)

During a primary THA, restoring the anatomic femoral offset (the horizontal distance from the center of rotation to the femoral anatomic axis) has which of the following biomechanical effects?

. Increases the abductor moment arm and decreases the joint reactive force
. Decreases the abductor moment arm and increases the joint reactive force
. Increases both the abductor moment arm and the joint reactive force
. Decreases the tension on the soft tissues, increasing dislocation risk
. Shifts the center of gravity medially

Correct Answer & Explanation

. Increases the abductor moment arm and decreases the joint reactive force

Explanation

Restoring or slightly increasing femoral offset increases the mechanical advantage (moment arm) of the abductor musculature. By the equation of static equilibrium in the coronal plane, an increased abductor moment arm means less abductor force is required to keep the pelvis level during the single-leg stance phase of gait. This subsequently decreases the overall compressive joint reactive force across the hip.

Question 5331

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with acute, severe medial-sided knee pain occurring after a minor twisting injury. Radiographs are normal, but an MRI demonstrates a subchondral crescent sign and bone marrow edema strictly localized to the weight-bearing surface of the medial femoral condyle.

This condition is most strongly associated with which of the following concurrent pathologies?

. Posterior root tear of the medial meniscus
. Anterior cruciate ligament complete rupture
. Lateral meniscal cyst
. Patellar tendinopathy
. Systemic lupus erythematosus treated with chronic corticosteroids

Correct Answer & Explanation

. Posterior root tear of the medial meniscus

Explanation

The clinical picture describes Spontaneous Osteonecrosis of the Knee (SPONK), also known as subchondral insufficiency fracture of the knee (SIFK). It overwhelmingly affects the medial femoral condyle in older females. Recent literature demonstrates a very strong association between SPONK and medial meniscus posterior root tears, which abruptly disrupt hoop stresses, leading to localized articular overloading and subsequent subchondral insufficiency fracture.

Question 5332

Topic: Total Knee Arthroplasty (TKA)

A 55-year-old male is evaluated for a primary TKA. He has an extra-articular deformity due to a previous midshaft femur fracture that healed with 25 degrees of coronal plane varus malunion. When planning the TKA, what is the most important consideration regarding the management of this extra-articular deformity?

. Coronal deformities greater than 20 degrees typically cannot be managed by intra-articular resection alone and require an extra-articular corrective osteotomy
. A standard intramedullary femoral alignment guide will accurately recreate the mechanical axis
. The deformity can be ignored if the patient's collateral ligaments are intact
. The femur should be cut perpendicular to its anatomic axis regardless of the deformity
. A highly constrained hinge prosthesis is mandatory without osteotomy

Correct Answer & Explanation

. Coronal deformities greater than 20 degrees typically cannot be managed by intra-articular resection alone and require an extra-articular corrective osteotomy

Explanation

Extra-articular deformities of the femur or tibia must be carefully evaluated before TKA. Generally, a coronal plane deformity >20 degrees (or sagittal >20 degrees) too close to the joint cannot be compensated for entirely with intra-articular bone cuts and soft tissue balancing without compromising the collateral ligament insertions or violating the envelope of the joint. These cases typically require an extra-articular corrective osteotomy (often performed as a staged or concurrent procedure).

Question 5333

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male is 1 year post-TKA and complains of recurrent knee swelling, pain when rising from a chair, and a feeling that the knee is 'giving way' specifically when descending stairs. Physical exam reveals a well-healed incision, no varus/valgus instability in full extension, but significant anteroposterior laxity at 90 degrees of knee flexion. Radiographs show well-fixed components with no loosening. What is the most likely etiology?

. Flexion instability secondary to a loose flexion gap (e.g., undersized femoral component)
. Recurrent periprosthetic joint infection
. Extensor mechanism rupture
. Mid-flexion instability due to joint line elevation
. Global instability secondary to severe poly wear

Correct Answer & Explanation

. Flexion instability secondary to a loose flexion gap (e.g., undersized femoral component)

Explanation

The classic presentation of flexion instability post-TKA includes recurrent effusions, instability specifically descending stairs (which requires quadriceps eccentric control in flexion), and difficulty rising from a chair. Physical exam demonstrates a loose flexion gap (AP laxity at 90 degrees) while the extension gap is stable. This is often caused by an undersized femoral component, excessive posterior slope, or failure to balance the PCL in a cruciate-retaining knee.

Question 5334

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following conditions is widely considered an absolute contraindication to metal-on-metal Hip Resurfacing Arthroplasty (HRA)?

. Chronic kidney disease with reduced glomerular filtration rate
. Male gender with primary osteoarthritis
. Avascular necrosis with less than 30% femoral head involvement
. Body mass index > 35
. Age younger than 50 years

Correct Answer & Explanation

. Chronic kidney disease with reduced glomerular filtration rate

Explanation

Metal-on-metal (MoM) hip resurfacings generate metal ions (cobalt and chromium) that are primarily excreted by the kidneys. Chronic kidney disease (renal failure) is an absolute contraindication because the patient cannot adequately clear these ions, leading to systemic metal toxicity. Other contraindications include females of childbearing age, severe osteoporosis, and large structural cysts in the femoral head.

Question 5335

Topic: Total Knee Arthroplasty (TKA)

During a primary TKA, the popliteal artery is most vulnerable to direct traumatic injury. At what anatomical level relative to the joint line is the popliteal artery most tethered and closest to the posterior capsule, increasing its risk of injury from an oscillating saw?

. Just posterior to the proximal tibia during the tibial resection
. At the level of the adductor hiatus
. Posterior to the femoral condyles during the posterior chamfer cut
. Deep to the medial collateral ligament
. Within the substance of the popliteus muscle belly

Correct Answer & Explanation

. Just posterior to the proximal tibia during the tibial resection

Explanation

The popliteal artery is at greatest risk of direct injury during the flat proximal tibial bone cut. It is tethered closely to the posterior capsule by the fibrous arch of the soleus muscle just distal to the joint line. An oscillating saw penetrating the posterior capsule or an improperly placed posterior retractor behind the tibia can directly lacerate or avulse the artery.

Question 5336

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old patient presents with acute onset of severe left knee pain, swelling, and fever 2 years after a primary TKA. Symptoms began 5 days ago. Aspiration yields 85,000 WBC/uL with 95% neutrophils. Radiographs show a well-fixed TKA. The surgeon opts for DAIR (Debridement, Antibiotics, and Implant Retention). To optimize the success rate of this procedure, which surgical principle is paramount?

. Exchange of the modular polyethylene insert
. Retention of the original polyethylene to maintain soft tissue balance
. Immediate administration of empiric antibiotics prior to intraoperative cultures
. Arthroscopic rather than open debridement to minimize morbidity
. Application of a negative pressure wound therapy device directly into the joint space

Correct Answer & Explanation

. Exchange of the modular polyethylene insert

Explanation

In the setting of an acute hematogenous periprosthetic joint infection (symptoms <3 weeks in a previously well-functioning, well-fixed joint), DAIR is indicated. The success of DAIR is significantly improved by performing a thorough OPEN debridement (arthroscopy is inadequate) and strictly exchanging the modular polyethylene insert. Exchanging the poly allows access to the posterior recess of the knee for thorough debridement and removes bacteria adhering to the poly.

Question 5337

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following patients represents the most appropriate candidate for an isolated patellofemoral arthroplasty (PFA)?

. A 50-year-old with isolated patellofemoral osteoarthritis, an intact ACL, and normal tibiofemoral alignment
. A 55-year-old with patellofemoral osteoarthritis and a fixed 10-degree valgus tibiofemoral deformity
. A 60-year-old with rheumatoid arthritis primarily affecting the anterior compartment
. A 45-year-old with isolated patellofemoral osteoarthritis and a chronic ACL rupture
. A 65-year-old with chondromalacia patellae and complex regional pain syndrome

Correct Answer & Explanation

. A 50-year-old with isolated patellofemoral osteoarthritis, an intact ACL, and normal tibiofemoral alignment

Explanation

Ideal candidates for isolated patellofemoral arthroplasty (PFA) have isolated anterior compartment osteoarthritis. Strict prerequisites include intact knee ligaments (ACL is crucial to prevent abnormal kinematics and rapid wear), normal tibiofemoral alignment (varus or valgus deformities overload the other compartments leading to rapid failure), and absence of inflammatory arthropathy (which will invariably progress to involve the entire joint).

Question 5338

Topic: Total Knee Arthroplasty (TKA)

A 60-year-old male presents with severe stiffness 8 weeks following an uncomplicated primary TKA. His active range of motion is 10 to 65 degrees. Physical therapy has plateaued. The components are correctly sized and positioned on radiographs. If a manipulation under anesthesia (MUA) is planned, what does the literature suggest regarding its timing and efficacy?

. MUA is most effective when performed between 6 to 12 weeks postoperatively
. MUA should be delayed until at least 6 months postoperatively to allow capsular healing
. MUA carries a 50% risk of extensor mechanism rupture and is generally contraindicated
. Open arthrolysis should always precede MUA in this timeframe
. MUA is only effective for correcting extension deficits, not flexion deficits

Correct Answer & Explanation

. MUA is most effective when performed between 6 to 12 weeks postoperatively

Explanation

Manipulation under anesthesia (MUA) is the primary treatment for arthrofibrosis (stiffness) post-TKA after a trial of conservative therapy has failed. It is most successful when performed within the 'window' of 6 to 12 weeks post-surgery. After 12 weeks, the intra-articular scar tissue becomes excessively mature and dense, significantly reducing the efficacy of MUA and increasing the risk of complications like periprosthetic fracture or extensor mechanism rupture.

Question 5339

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female with severe lumbar flatback deformity and spinal fusion from T10-Pelvis is undergoing a primary total hip arthroplasty. How should the acetabular component placement be adjusted compared to a patient with normal spinopelvic mobility?

. Decrease anteversion and inclination
. Target standard 15 degrees of anteversion and 40 degrees of inclination
. Increase retroversion
. Increase anteversion and inclination
. Decrease inclination only

Correct Answer & Explanation

. Decrease anteversion and inclination

Explanation

Patients with a stiff spine cannot accommodate to sitting by posteriorly tilting their pelvis. To prevent posterior dislocation during hip flexion, the acetabular cup must be placed in increased anteversion and inclination.

Question 5340

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty for a fixed 15-degree valgus deformity, after the initial bone cuts are made, the knee is tight laterally in flexion but perfectly balanced in extension. Which structure should be released to specifically address this mismatch?

. Lateral collateral ligament
. Iliotibial band
. Posterolateral capsule
. Lateral head of gastrocnemius
. Popliteus tendon

Correct Answer & Explanation

. Lateral collateral ligament

Explanation

The popliteus tendon is a primary lateral stabilizer in flexion but not in extension. Releasing it selectively addresses a tight lateral flexion gap without affecting the balanced extension gap.

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