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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 255 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 5081

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with thigh pain 10 years after a cementless total hip arthroplasty. Radiographs demonstrate a continuous radiolucent line of 3 mm with sclerotic margins in Gruen zones 1, 2, 6, and 7. The stem has subsided by 5 mm. What is the most likely mode of failure?

. Infection
. Aseptic loosening due to particulate debris
. Stress shielding
. Trunnionosis
. Peri-prosthetic fracture

Correct Answer & Explanation

. Infection

Explanation

The presence of a wide, continuous radiolucent line with a sclerotic boundary (demarcation) around a previously well-fixed stem, along with subsidence, is classic for aseptic loosening secondary to osteolysis from particulate debris (typically polyethylene wear). Stress shielding typically shows proximal bone resorption (calcar round-off) but with the distal stem remaining rigidly fixed without subsidence. Infection usually presents with more rapid, irregular osteolysis and periosteal reaction without a sclerotic border.

Question 5082

Topic: 3. Adult Reconstruction (Hip & Knee)

During a revision total knee arthroplasty, removal of the tibial component reveals a massive contained metaphyseal defect measuring 3 cm deep, but with an intact cortical rim. According to the Anderson Orthopaedic Research Institute (AORI) classification, what type of defect is this, and what is the preferred method of management?

. AORI Type 1; impaction bone grafting
. AORI Type 2A; cement fill
. AORI Type 2B; cemented short stem
. AORI Type 2; porous metaphyseal cone or sleeve with a diaphyseal stem
. AORI Type 3; custom hinged prosthesis

Correct Answer & Explanation

. AORI Type 1; impaction bone grafting

Explanation

A massive metaphyseal defect (cavitary) with an intact cortical rim is an AORI Type 2 defect (often 2B if both condyles are involved, 2A if single). For large Type 2 defects that are not amenable to simple cement fill or small block augments, the use of porous metaphyseal tantalum cones or titanium sleeves combined with a diaphyseal engaging stem provides excellent structural support and long-term biologic fixation.

Question 5083

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old patient who underwent a posterior-stabilized total knee arthroplasty 1 year ago complains of a painful 'catch' and an audible pop at the anterior knee when extending the leg from roughly 40 degrees of flexion to full extension. What is the underlying pathomechanics of this condition?

. A fibrous nodule forming at the superior pole of the patella engaging the intercondylar box
. Impingement of the patellar component on an over-resected anterior femoral flange
. Subluxation of the patella due to a tight lateral retinaculum
. The posterior cam engaging the tibial post too early in flexion
. Loose body in the lateral gutter

Correct Answer & Explanation

. A fibrous nodule forming at the superior pole of the patella engaging the intercondylar box

Explanation

Patellar clunk syndrome is a known complication specific to posterior-stabilized TKA designs. It occurs when a fibrous nodule hypertrophies at the junction of the quadriceps tendon and the superior pole of the patella. During flexion, the nodule drops into the intercondylar box of the femoral component. As the knee extends (usually between 30-45 degrees), the nodule catches on the superior margin of the box and suddenly pops out, creating the characteristic painful 'clunk'. Treatment is typically arthroscopic debridement of the nodule.

Question 5084

Topic: Total Knee Arthroplasty (TKA)

During primary total knee arthroplasty using a measured resection technique, the surgeon aims to restore the joint line. Which of the following anatomic landmarks is most reliable for approximating the native joint line level if the articular surface is severely distorted?

. 3 cm distal to the medial epicondyle
. 10 mm distal to the fibular head
. 2.5 to 3 cm distal to the adductor tubercle
. 15 mm proximal to the tibial tubercle
. Level with the inferior pole of the patella in extension

Correct Answer & Explanation

. 3 cm distal to the medial epicondyle

Explanation

In revision TKA or primary TKA with severe bone loss/distortion, restoring the joint line is critical for proper kinematics and patellar tracking. Reliable osseous landmarks for estimating the joint line include: ~2.5 to 3 cm distal to the adductor tubercle, ~2.5 cm distal to the medial epicondyle, and ~1.5 cm proximal to the fibular head. Option 0 (3 cm from medial epicondyle) is slightly inaccurate (usually 2.5 cm). The adductor tubercle is a very consistent landmark, and the joint line sits approximately 2.5 to 3 cm distal to it.

Question 5085

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male presents with groin pain 8 years after a metal-on-metal total hip arthroplasty. Lab results show elevated serum cobalt and chromium levels. MRI with MARS (Metal Artifact Reduction Sequence) shows a solid and cystic mass communicating with the joint space. What is the characteristic histological finding in the periprosthetic tissue of this condition?

. Diffuse infiltrate of neutrophils
. Extensive aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)
. Abundant birefringent polyethylene wear debris with macrophages
. Osteoclastic resorption with numerous foreign-body giant cells engulfing PMMA
. Eosinophilic granuloma

Correct Answer & Explanation

. Diffuse infiltrate of neutrophils

Explanation

Adverse local tissue reactions (ALTR) in metal-on-metal (MoM) implants are characterized by ALVAL (Aseptic Lymphocyte-dominated Vasculitis-Associated Lesion). Histologically, it shows a diffuse perivascular infiltrate of T-lymphocytes and plasma cells. Birefringent particles under polarized light are seen with polyethylene wear, while giant cells engulfing non-birefringent debris are typical of PMMA (cement) wear.

Question 5086

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty for a severe fixed valgus deformity, the knee is noted to be tight in extension but balanced in flexion. Which of the following lateral structures should be released first to selectively correct the tight extension gap?

. Popliteus tendon
. Lateral collateral ligament (LCL)
. Iliotibial band (ITB)
. Posterior cruciate ligament (PCL)
. Lateral retinaculum

Correct Answer & Explanation

. Popliteus tendon

Explanation

The iliotibial (IT) band is a primary stabilizer in extension on the lateral side. In a valgus knee that is tight in extension but balanced in flexion, the IT band should be released first. The popliteus tendon is tight in flexion, and releasing it would primarily affect the flexion gap.

Question 5087

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old female sustains a fall 5 years after a cementless THA. Radiographs show a periprosthetic femur fracture occurring around the stem tip. Intraoperative assessment reveals the stem remains firmly fixed in the metaphysis, and the proximal bone stock is adequate. According to the Vancouver classification, what is the fracture type and the standard recommended treatment?

. Type B1; Open reduction and internal fixation (ORIF) with cables and a plate
. Type B2; Revision to a long cementless diaphyseal-engaging stem
. Type B3; Revision with a proximal femoral replacement
. Type C; ORIF using a lateral plate alone
. Type A; Conservative management with protected weight-bearing

Correct Answer & Explanation

. Type B1; Open reduction and internal fixation (ORIF) with cables and a plate

Explanation

The fracture is around the stem (Type B). Because the stem is firmly fixed, it is classified as a Vancouver B1 fracture. The standard treatment for B1 fractures is ORIF using a long plate, bridging the fracture with bicortical fixation distally and unicortical screws or cerclage cables proximally.

Question 5088

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old female presents with an inability to perform a straight leg raise 3 months following a primary TKA. Examination reveals a palpable gap at the superior pole of the patella. What is the most appropriate surgical management for this complication?

. Primary end-to-end repair with nonabsorbable sutures
. Patellectomy and advancement of the quadriceps tendon
. Reconstruction using a synthetic mesh or extensor mechanism allograft
. Revision TKA with a hinged prosthesis
. Cylinder cast immobilization in extension for 6 weeks

Correct Answer & Explanation

. Primary end-to-end repair with nonabsorbable sutures

Explanation

Quadriceps tendon ruptures (or any major extensor mechanism disruption) following TKA have very high failure rates with simple primary end-to-end repair due to poor tissue quality and tension. Reconstruction using an extensor mechanism allograft or synthetic mesh (e.g., Marlex mesh) is the recommended treatment to provide a durable biologic or synthetic scaffold.

Question 5089

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is traditionally considered an absolute contraindication to a medial mobile-bearing unicompartmental knee arthroplasty (UKA)?

. Age greater than 60 years
. BMI greater than 30
. Anterior cruciate ligament (ACL) deficiency
. Asymptomatic patellofemoral osteoarthritis
. Fixed flexion deformity of 10 degrees

Correct Answer & Explanation

. Age greater than 60 years

Explanation

ACL deficiency is traditionally an absolute contraindication for a mobile-bearing medial UKA due to the high risk of bearing spin-out and abnormal anterior-posterior kinematics. Age and weight are no longer considered absolute contraindications. Mild fixed flexion contractures (<15 degrees) and asymptomatic patellofemoral osteoarthritis are widely accepted in modern UKA practice.

Question 5090

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male complains of a painful catching sensation and an audible "clunk" when extending his knee from a flexed position, 1 year after a posterior-stabilized (PS) TKA. What is the primary etiology of this condition?

. Oversized femoral component causing overstuffing
. Fibrous nodule formation at the superior pole of the patella engaging the intercondylar box
. Polyethylene wear of the tibial post
. Asymmetric resection of the patella
. Laxity of the medial collateral ligament

Correct Answer & Explanation

. Oversized femoral component causing overstuffing

Explanation

Patellar clunk syndrome is a complication predominantly seen in PS TKA designs. It is caused by the formation of a fibrous nodule at the junction of the quadriceps tendon and the superior pole of the patella. During flexion, this nodule drops into the intercondylar box of the femoral component. As the knee extends (usually around 30-45 degrees), the nodule pops out with a painful "clunk".

Question 5091

Topic: Total Knee Arthroplasty (TKA)



A patient presents with a feeling of the knee "giving way" when descending stairs 1 year post-TKA. On examination, the knee is stable in full extension but has significant anteroposterior laxity at 90 degrees of flexion. Which of the following technical errors during the index surgery is the most likely cause?

. Oversized femoral component
. Excessive distal femoral resection
. Undersized femoral component with excessive posterior condylar resection
. Excessive proximal tibial resection
. Isolated medial collateral ligament rupture

Correct Answer & Explanation

. Oversized femoral component

Explanation

Flexion instability is characterized by laxity in flexion while maintaining stability in extension. It is typically caused by an excessive resection of the posterior femoral condyles or the use of an undersized femoral component, leading to a loose flexion gap. Compensating by using a thicker polyethylene insert would result in a tight extension gap.

Question 5092

Topic: Total Knee Arthroplasty (TKA)

During a primary TKA for a varus osteoarthritic knee, after making the standard measured bone cuts, the knee has a symmetric tight medial gap in both flexion and extension. The lateral gap is well-balanced. Which of the following is the most appropriate next step in soft tissue balancing?

. Release the iliotibial band (ITB)
. Downsize the femoral component
. Release the deep medial collateral ligament (MCL) and posteromedial capsule
. Recut the proximal tibia with more valgus alignment
. Increase the polyethylene insert thickness

Correct Answer & Explanation

. Release the iliotibial band (ITB)

Explanation

A tight medial gap in both flexion and extension indicates a symmetrically tight medial compartment. The most appropriate step is to release the medial structures, typically starting with the deep MCL and posteromedial capsule. Modifying bone cuts is not indicated if the mechanical axis cuts were correct, and increasing poly thickness would overstuff the entire joint.

Question 5093

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old female undergoes a right TKA for a severe fixed valgus deformity. Postoperatively in the recovery room, she is noted to have a foot drop and decreased sensation over the dorsum of the right foot. What is the most appropriate initial management?

. Immediate surgical exploration and neurolysis of the common peroneal nerve
. Removal of the compressive knee dressing, flexion of the knee to 20-30 degrees, and application of an AFO
. Revision TKA to loosen the lateral collateral ligament
. Electromyography (EMG) and nerve conduction studies
. Administration of high-dose intravenous corticosteroids

Correct Answer & Explanation

. Immediate surgical exploration and neurolysis of the common peroneal nerve

Explanation

Peroneal nerve palsy is a known complication of TKA in patients with severe valgus and flexion contractures, primarily due to traction on the nerve upon deformity correction. Initial management includes relieving any extrinsic pressure (loosening dressings) and relaxing the nerve by flexing the knee to 20-30 degrees. An AFO prevents equinus contracture. Surgical exploration is generally reserved for failure to recover after several months.

Question 5094

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the classic work by Lewinnek, what is the "safe zone" for the orientation of the acetabular component in total hip arthroplasty to minimize the risk of postoperative dislocation?

. 15° ± 10° of anteversion and 40° ± 10° of inclination
. 30° ± 10° of anteversion and 50° ± 10° of inclination
. 15° ± 10° of retroversion and 40° ± 10° of inclination
. 25° ± 10° of anteversion and 30° ± 10° of inclination
. 10° ± 5° of anteversion and 45° ± 5° of inclination

Correct Answer & Explanation

. 15° ± 10° of anteversion and 40° ± 10° of inclination

Explanation

Lewinnek et al. described the safe zone for acetabular cup placement as 15° ± 10° of anteversion and 40° ± 10° of inclination (abduction). Placement of the cup outside this zone historically correlated with a significantly higher risk of dislocation, though modern large-head bearings have slightly altered these strict functional parameters.

Question 5095

Topic: Total Knee Arthroplasty (TKA)

Which of the following statements best describes the surgical principle of true kinematic alignment in total knee arthroplasty?

. Making femoral and tibial bone cuts strictly perpendicular to the mechanical axis of the lower extremity
. Restoring the pre-arthritic constitutional alignment of the knee by matching the patient's individual anatomy
. Creating a neutral mechanical axis (0 degrees of hip-knee-ankle angle) in all patients to equalize load distribution
. Using a computer-navigated system to assure exactly 3 degrees of varus in the tibial cut for all patients
. Extensively releasing the collateral ligaments to create equal rectangular gaps before making any bone cuts

Correct Answer & Explanation

. Making femoral and tibial bone cuts strictly perpendicular to the mechanical axis of the lower extremity

Explanation

Kinematic alignment (KA) aims to restore the patient's native, pre-arthritic constitutional joint lines and alignment (co-alignment of the kinematic axes of the knee). This involves making bone cuts that match the individual anatomy, often leaving the tibia in slight varus and the femur in slight valgus. This is in contrast to mechanical alignment, which aims for a neutral (0-degree) mechanical axis.

Question 5096

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male presents with groin pain 6 years after a primary THA using a large-diameter metal head on a standard titanium alloy stem (metal-on-polyethylene bearing). Radiographs show no component loosening, but an MRI reveals a large cystic mass around the joint. Blood tests show elevated serum cobalt and normal chromium levels. What is the most likely diagnosis?

. Aseptic loosening of the acetabular component
. Adverse local tissue reaction (ALTR) secondary to mechanically assisted crevice corrosion (trunnionosis)
. Recurrent micro-dislocation
. Polyethylene wear-induced osteolysis
. Chronic periprosthetic joint infection (PJI)

Correct Answer & Explanation

. Aseptic loosening of the acetabular component

Explanation

Trunnionosis, or mechanically assisted crevice corrosion (MACC), occurs at the modular head-neck junction. It is a known complication when using large metal heads (often cobalt-chromium) on titanium stems. The localized corrosion releases metal ions (typically higher cobalt than chromium), leading to an adverse local tissue reaction (ALTR) or pseudotumor, even without a metal-on-metal bearing surface.

Question 5097

Topic: 3. Adult Reconstruction (Hip & Knee)
A 35-year-old male presents with right hip pain. MRI confirms avascular necrosis (AVN) of the femoral head. Radiographs show a distinct sclerotic band and cystic changes in the femoral head, but no subchondral collapse or crescent sign. According to the Ficat and Arlet classification, what stage is this, and is core decompression generally indicated?
. Stage I; Core decompression is contraindicated
. Stage II; Core decompression is an appropriate treatment option
. Stage III; Core decompression is an appropriate treatment option
. Stage IV; Total hip arthroplasty is the only option
. Stage 0; Observation only is indicated

Correct Answer & Explanation

. Stage II; Core decompression is an appropriate treatment option

Explanation

The presence of radiographic changes (sclerosis/cysts) without subchondral collapse (no crescent sign or flattening) corresponds to Ficat Stage II AVN. Core decompression is generally indicated for early, pre-collapse stages (Ficat I and II) to reduce intraosseous pressure, improve vascularity, and attempt to delay or prevent progression to collapse.

Question 5098

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, a single-wedge (flat tapered) titanium cementless stem relies primarily on which of the following mechanisms for its initial mechanical stability?

. Diaphyseal scratch fit
. Mediolateral three-point fixation in the proximal metaphysis
. Distal cortical engagement
. Anterior-posterior metaphyseal fill
. Cement interdigitation

Correct Answer & Explanation

. Diaphyseal scratch fit

Explanation

Single-wedge (flat tapered) stems, such as the Taperloc or Accolade, are designed to wedge mediolaterally within the proximal femur (metaphysis) to achieve three-point fixation. They are purposefully narrow in the AP dimension to spare bone and do not rely on AP fill or distal diaphyseal engagement, which helps prevent stress shielding.

Question 5099

Topic: Total Knee Arthroplasty (TKA)

During a complex revision TKA, the surgeon notes profound laxity and attenuation of the medial collateral ligament (MCL) such that the knee cannot be balanced coronally in either flexion or extension. The extensor mechanism and posterior capsule remain completely intact. Which level of prosthetic constraint is most appropriate in this scenario?

. Cruciate-retaining (CR)
. Posterior-stabilized (PS)
. Constrained non-hinged (CCK / VVC)
. Rotating-hinge
. Unicompartmental

Correct Answer & Explanation

. Cruciate-retaining (CR)

Explanation

A completely deficient or non-functional MCL that prevents coronal balancing is an indication for a rotating-hinge prosthesis. A constrained non-hinged (CCK/VVC) implant requires an intact or minimally competent MCL and LCL to act as a soft-tissue tether; it cannot overcome profound global collateral deficiency.

Question 5100

Topic: 3. Adult Reconstruction (Hip & Knee)

In revision total hip arthroplasty (THA), an Extended Trochanteric Osteotomy (ETO) is often planned to remove a well-fixed cementless stem. To ensure successful extraction and subsequent stable fixation of a fully porous-coated cylindrical revision stem, what is the biomechanical principle regarding the length of the ETO fragment?

. It must end at least 2 cm proximal to the tip of the primary stem.
. It should extend just distal to the extent of the porous coating or fixation of the stem to be removed.
. It must be limited to the greater trochanter to preserve the gluteus medius insertion.
. It should bypass the tip of the primary stem by exactly 2 femoral diaphyseal diameters.
. It must end exactly at the lesser trochanter regardless of stem length.

Correct Answer & Explanation

. It must end at least 2 cm proximal to the tip of the primary stem.

Explanation

An Extended Trochanteric Osteotomy (ETO) must extend distal to the area of prosthetic fixation to allow for safe extraction of a well-fixed cementless stem (or distal to the cement mantle for cemented stems). For reimplantation, the diaphyseal segment of the revision stem must achieve at least 4 to 6 cm of scratch fit distal to the ETO osteotomy site.

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