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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 90 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 1781

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old male presents with inability to actively extend his knee 3 years following a primary TKA. Examination reveals a palpable gap at the patellar tendon. What is the most reliable reconstructive option for this chronic, massive disruption?

. Primary end-to-end repair with non-absorbable suture
. Synthetic mesh (e.g., Marlex) reconstruction or whole extensor mechanism allograft
. Autologous hamstring tendon reconstruction
. Medial gastrocnemius rotational flap alone
. Isolated V-Y quadricepsplasty

Correct Answer & Explanation

. Synthetic mesh (e.g., Marlex) reconstruction or whole extensor mechanism allograft

Explanation

Chronic extensor mechanism disruptions post-TKA have extremely high failure rates with direct repair. Synthetic mesh (Marlex) reconstruction or a complete extensor mechanism allograft are the gold standards for restoring function.

Question 1782

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following surgical modifications most significantly decreases the risk of postoperative dislocation in primary total hip arthroplasty?

. Using a 28 mm instead of a 32 mm femoral head
. Decreasing the acetabular component offset
. Utilizing an anterolateral approach over a direct anterior approach
. Increasing femoral head size from 28 mm to 36 mm
. Positioning the acetabular component in 5 degrees of anteversion

Correct Answer & Explanation

. Increasing femoral head size from 28 mm to 36 mm

Explanation

Increasing femoral head size increases the jump distance and improves the head-to-neck ratio, significantly reducing the risk of impingement and subsequent dislocation. The direct anterior and anterolateral approaches generally have comparable low baseline dislocation rates.

Question 1783

Topic: Total Hip Arthroplasty (THA)

During preoperative templating for a total hip arthroplasty, the surgeon notes a 15 mm functional leg length discrepancy (affected side short) and a 10 mm anatomic true leg length discrepancy (affected side short). To avoid symptomatic over-lengthening postoperatively, the surgeon should aim to restore:

. Only the functional leg length discrepancy (15 mm)
. Only the anatomic true leg length discrepancy (10 mm)
. The sum of both discrepancies (25 mm)
. Global offset instead of length, ignoring the discrepancy
. A net shortening of the limb to relax the sciatic nerve

Correct Answer & Explanation

. Only the anatomic true leg length discrepancy (10 mm)

Explanation

The goal of THA is to restore true anatomic leg length. Functional leg length discrepancies are often due to pelvic obliquity from spine pathology or soft tissue contractures, which typically adapt over time; correcting to functional length leads to true anatomic over-lengthening.

Question 1784

Topic: Total Knee Arthroplasty (TKA)

A 60-year-old female scheduled for primary TKA reports a severe blistering skin reaction to inexpensive jewelry. Patch testing confirms a severe nickel allergy. Which of the following femoral component materials is most appropriate to prevent a hypersensitivity reaction?

. Cobalt-chromium-molybdenum alloy
. Surgical grade stainless steel
. Oxidized zirconium (Oxinium) or Titanium-based implant
. Standard uncoated cobalt-chromium
. Porous tantalum with cobalt-chromium condyles

Correct Answer & Explanation

. Oxidized zirconium (Oxinium) or Titanium-based implant

Explanation

Patients with severe, documented metal allergies (like nickel) should receive hypoallergenic implants. Oxidized zirconium (Oxinium) or purely titanium-based components contain minimal to no nickel and are considered safe alternatives to standard cobalt-chromium alloys.

Question 1785

Topic: Total Hip Arthroplasty (THA)

A 74-year-old female presents for revision THA. Radiographs demonstrate an inferiorly migrated acetabular component, a transverse radiolucent line across the posterior column, and an ilioischial line break. Intraoperatively, the superior and inferior hemi-pelves move independently. Which of the following is the most appropriate reconstructive technique?

. Standard hemispherical porous-coated cup with multiple dome screws
. Impaction bone grafting and a cemented polyethylene cup
. Cup-cage construct or custom triflange acetabular component
. Bilobed (oblong) uncemented cup without supplementary fixation
. Jumbo uncemented cup alone

Correct Answer & Explanation

. Standard hemispherical porous-coated cup with multiple dome screws

Explanation

Independent movement of the superior and inferior hemi-pelves indicates pelvic discontinuity. Reconstructive options must stabilize the two halves, typically requiring a cup-cage construct, a custom triflange component, or highly porous metal augments with a distraction technique.

Question 1786

Topic: Total Hip Arthroplasty (THA)

A 68-year-old female presents with recurrent episodes of anterior hip dislocation following a primary total hip arthroplasty. Her dislocations typically occur when she extends and externally rotates her hip while walking. Which of the following component malpositions is the most likely cause of this specific instability pattern?

. Retroverted acetabular component and retroverted femoral stem
. Excessively anteverted acetabular component and retroverted femoral stem
. Excessively anteverted acetabular component and excessively anteverted femoral stem
. Retroverted acetabular component and anteverted femoral stem
. Excessively abducted acetabular component with neutral femoral stem version

Correct Answer & Explanation

. Retroverted acetabular component and retroverted femoral stem

Explanation

Excessive combined anteversion of the acetabular and femoral components leads to anterior instability. This typically occurs in extension and external rotation, as the components lever against each other anteriorly.

Question 1787

Topic: Total Hip Arthroplasty (THA)

A 65-year-old female undergoes primary total hip arthroplasty (THA) via a posterior approach. Post-operatively, she experiences recurrent anterior dislocations.

Which of the following component malpositions is the most likely cause of her anterior instability?

. Excessive femoral retroversion
. Excessive acetabular retroversion
. Excessive combined anteversion
. Inadequate femoral offset
. Leg length discrepancy with a short operative leg

Correct Answer & Explanation

. Excessive combined anteversion

Explanation

Anterior dislocation of a THA is most commonly caused by excessive combined anteversion (acetabular anteversion + femoral anteversion). When the combined anteversion is too high, the femoral head is driven anteriorly out of the acetabulum, especially during hip extension and external rotation. Conversely, excessive retroversion typically leads to posterior instability.

Question 1788

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male presents with global knee stiffness 6 months after a primary total knee arthroplasty (TKA). His range of motion is 15 to 70 degrees. Radiographs demonstrate appropriate component sizing, but the joint line has been elevated by 8 mm compared to the contralateral knee.

What is the most likely biomechanical consequence of elevating the joint line in TKA?

. Pseudo-patella baja and decreased knee flexion
. Patella alta and increased knee flexion
. Patellar subluxation due to medialization
. Hyperextension instability
. Mid-flexion instability only

Correct Answer & Explanation

. Pseudo-patella baja and decreased knee flexion

Explanation

Elevating the joint line during TKA (often due to excessive distal femoral resection compensated by a thicker polyethylene insert) leads to a condition known as pseudo-patella baja. The patella sits lower relative to the elevated joint line, which alters patellofemoral kinematics, causes patellar impingement against the tibial insert, and significantly decreases postoperative knee flexion.

Question 1789

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old active female sustains a displaced femoral neck fracture (Garden IV). When counseling her on surgical options, comparing total hip arthroplasty (THA) to hemiarthroplasty, THA is associated with which of the following outcomes?

. Lower risk of dislocation
. Lower rate of reoperation
. Shorter surgical time
. Less intraoperative blood loss
. Higher incidence of groin pain

Correct Answer & Explanation

. Lower rate of reoperation

Explanation

For active, independent elderly patients with a displaced femoral neck fracture, Total Hip Arthroplasty (THA) provides superior long-term functional outcomes and lower reoperation rates compared to hemiarthroplasty. Hemiarthroplasty has a higher reoperation rate primarily due to subsequent acetabular wear and erosion. However, THA does carry a higher risk of dislocation, longer operative time, and greater blood loss than hemiarthroplasty.

Question 1790

Topic: Total Hip Arthroplasty (THA)

A 65-year-old male is 3 months post-operative from a primary total hip arthroplasty (THA) via a posterior approach. He presents with a history of three posterior dislocations. Radiographs demonstrate a well-fixed acetabular component with 45 degrees of abduction and 20 degrees of anteversion. The femoral stem is stable but appears retroverted by 10 degrees. What is the most appropriate surgical intervention to definitively address this instability?

. Prescribe a rigid hip abduction orthosis for 3 months
. Revise the acetabular component to increase anteversion to 35 degrees
. Revise the femoral component to increase anteversion
. Revise the acetabular liner to a constrained liner design
. Perform a greater trochanteric advancement

Correct Answer & Explanation

. Revise the femoral component to increase anteversion

Explanation

Combined anteversion is the critical factor in preventing THA instability. The ideal combined anteversion is typically 25 to 35 degrees for males. The acetabular component is already well-positioned (45 deg abduction, 20 deg anteversion). The femoral stem, however, is in 10 degrees of retroversion, resulting in a low combined anteversion (10 degrees total) that predisposes the patient to posterior dislocation. Revising the femoral component to appropriate anteversion (10-15 degrees) restores normal biomechanics. Over-anteverting the cup (Option B) can lead to anterior instability. A constrained liner (Option D) is a salvage option but does not address the underlying significant malposition.

Question 1791

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female is 5 years status post total knee arthroplasty (TKA). She complains of anterior knee pain and a "clunking" sensation when actively extending the knee from a flexed position. Physical examination reveals a palpable and audible clunk at roughly 35 degrees of knee flexion. Radiographs demonstrate a well-fixed posterior stabilized (PS) TKA with no evidence of loosening. What is the most likely diagnosis?

. Asymmetric polyethylene wear
. Patellar clunk syndrome
. Aseptic loosening of the tibial tray
. Popliteus tendon snapping
. Extensor mechanism rupture

Correct Answer & Explanation

. Patellar clunk syndrome

Explanation

Patellar clunk syndrome is a complication seen primarily in posterior stabilized (PS) TKA designs. It is caused by the formation of a fibrotic tissue nodule at the superior pole of the patella or within the suprapatellar pouch. As the knee extends from a flexed position (usually around 30-45 degrees of flexion), this nodule catches in the intercondylar box of the femoral component and then abruptly pops out, creating a painful clunk. Treatment is typically arthroscopic debridement of the fibrotic nodule.

Question 1792

Topic: 3. Adult Reconstruction (Hip & Knee)
A 45-year-old male on chronic corticosteroids for systemic lupus erythematosus presents with severe groin pain. Plain radiographs show a crescent sign, and MRI confirms Ficat Stage III avascular necrosis (AVN) of the femoral head involving 45% of the weight-bearing area. What is the most reliable definitive surgical treatment for this patient?
. Core decompression with mesenchymal stem cell injection
. Free vascularized fibular graft
. Total hip arthroplasty (THA)
. Proximal femoral rotational osteotomy
. Arthroscopic joint debridement

Correct Answer & Explanation

. Total hip arthroplasty (THA)

Explanation

Ficat Stage III AVN is characterized by subchondral collapse (the 'crescent sign') with preserved joint space. Once the subchondral bone has mechanically collapsed, joint-preserving procedures such as core decompression or vascularized fibular grafting have a high failure rate and are generally no longer indicated, particularly for large lesions (>30% weight-bearing area). Total hip arthroplasty (THA) provides the most reliable pain relief and functional improvement for post-collapse AVN.

Question 1793

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with a grossly loose total hip arthroplasty and severe pelvic osteolysis. Preoperative evaluation suspects a pelvic discontinuity. Which of the following radiographic findings is the most reliable indicator of an ipsilateral pelvic discontinuity?

. Superior migration of the femoral head past the teardrop
. A visible transverse fracture line through the acetabulum with medial translation of the inferior hemipelvis
. Breakage of all previous acetabular dome screws
. Extensive heterotopic ossification bridging the greater trochanter and ilium
. An intact Kohler's line with protrusion of the acetabular component

Correct Answer & Explanation

. Superior migration of the femoral head past the teardrop

Explanation

Pelvic discontinuity is a complete separation of the superior half of the pelvis (ilium) from the inferior half (ischium and pubis) through the acetabulum. Radiographic signs include a visible transverse fracture line crossing the acetabulum and a medial translation of the inferior hemipelvis relative to the superior hemipelvis. Breakage of screws or superior migration indicates component loosening but not necessarily complete pelvic discontinuity.

Question 1794

Topic: 3. Adult Reconstruction (Hip & Knee)
A 60-year-old male with a metal-on-metal (MoM) total hip arthroplasty presents with new-onset groin pain and a palpable anterior thigh mass. Serum cobalt and chromium levels are elevated. MRI demonstrates a large fluid collection and cystic pseudotumor around the hip. What type of hypersensitivity reaction is primarily responsible for this adverse local tissue reaction (ALTR)?
. Type I (IgE-mediated immediate hypersensitivity)
. Type II (IgG/IgM cytotoxic reaction)
. Type III (Immune complex-mediated)
. Type IV (Delayed, T-cell mediated hypersensitivity)
. Foreign body macrophage granulomatous reaction

Correct Answer & Explanation

. Type IV (Delayed, T-cell mediated hypersensitivity)

Explanation

Adverse local tissue reactions (ALTR) or aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) associated with metal-on-metal bearing surfaces are primarily characterized as a Type IV delayed hypersensitivity reaction. This is a T-cell mediated immune response against metal ions (cobalt and chromium) that act as haptens, leading to massive perivascular lymphocytic infiltration, tissue necrosis, and pseudotumor formation.

Question 1795

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old woman presents with recurrent posterior dislocations of her total hip arthroplasty. Radiographic evaluation demonstrates an acetabular component positioned at 45 degrees of inclination and 0 degrees of anteversion.

Which of the following is the most appropriate surgical intervention to prevent further posterior dislocation?

. Revise the acetabular component to increase anteversion
. Revise the acetabular component to decrease inclination
. Revise the femoral component to decrease offset
. Exchange the modular head to increase neck length
. Perform a trochanteric advancement

Correct Answer & Explanation

. Revise the acetabular component to increase anteversion

Explanation

Posterior dislocation is most commonly associated with inadequate anteversion of the acetabular component. The target 'safe zone' (Lewinnek) is 40+/-10 degrees of inclination and 15+/-10 degrees of anteversion. Correcting the 0 degrees of anteversion to a more anteverted position will help prevent posterior dislocation.

Question 1796

Topic: Total Hip Arthroplasty (THA)

In ceramic-on-ceramic total hip arthroplasty, which of the following component malpositions is most strongly associated with the complication of squeaking?

. Femoral stem retroversion
. Acetabular component retroversion
. Excessive acetabular inclination
. Decreased femoral offset
. Excessive acetabular anteversion

Correct Answer & Explanation

. Femoral stem retroversion

Explanation

Squeaking in ceramic-on-ceramic THA is often attributed to edge loading or microseparation. Excessive acetabular inclination (a steep cup, typically >50 degrees) or extreme versions lead to edge loading, disrupting the fluid film lubrication, causing stripe wear, and resulting in squeaking.

Question 1797

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized (PS) total knee arthroplasty, trial reduction reveals that the knee is well-balanced in full extension but excessively tight in 90 degrees of flexion. Which of the following adjustments is the most appropriate next step?

. Downsize the femoral component and use a thicker polyethylene insert
. Recess the posterior cruciate ligament
. Release the posterior capsule
. Downsize the femoral component while maintaining the same anterior reference
. Increase the distal femoral resection

Correct Answer & Explanation

. Downsize the femoral component and use a thicker polyethylene insert

Explanation

A knee that is tight in flexion but balanced in extension has an isolated tight flexion gap. Options to increase the flexion gap without affecting the extension gap include downsizing the femoral component using anterior referencing (which removes more posterior condylar bone), dropping the posterior slope of the tibia (increases flexion gap more than extension), or translating the femoral component anteriorly. Increasing distal femoral resection would affect the extension gap.

Question 1798

Topic: Total Knee Arthroplasty (TKA)

A 60-year-old woman presents with isolated medial compartment knee osteoarthritis. Which of the following clinical or radiographic findings is a classic contraindication to performing a medial unicompartmental knee arthroplasty (UKA)?

. Patient age less than 65 years
. Flexion contracture of 10 degrees
. Deficient anterior cruciate ligament (ACL)
. Correctable varus deformity of 10 degrees
. Body mass index (BMI) of 32

Correct Answer & Explanation

. Patient age less than 65 years

Explanation

Classic indications/contraindications for UKA (Kozinn and Scott criteria) state that a deficient ACL is a contraindication to medial UKA because it leads to eccentric wear and early failure. While modern indications have expanded somewhat, ACL deficiency remains a strong classic contraindication for standard fixed-bearing UKA. Age and weight limits have largely been abandoned as strict contraindications.

Question 1799

Topic: 3. Adult Reconstruction (Hip & Knee)

Based on the 2018 International Consensus Meeting (ICM) on Periprosthetic Joint Infection criteria, which of the following synovial fluid profiles strongly supports the diagnosis of a chronic PJI following total hip arthroplasty?

. Synovial WBC 1,500 cells/uL, PMN 55%
. Synovial WBC 2,000 cells/uL, PMN 60%
. Synovial WBC 3,500 cells/uL, PMN 85%
. Synovial WBC 1,000 cells/uL, PMN 40%
. Synovial WBC 2,500 cells/uL, PMN 75%

Correct Answer & Explanation

. Synovial WBC 1,500 cells/uL, PMN 55%

Explanation

According to the 2018 ICM criteria, minor criteria for chronic PJI include elevated synovial fluid WBC (>3,000 cells/uL) and elevated PMN percentage (>80%). The values in option C (3,500 cells/uL, 85%) exceed these thresholds, strongly supporting the diagnosis of a chronic PJI.

Question 1800

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with a metal-on-metal total hip arthroplasty presents with new-onset groin pain and a palpable anterior mass 5 years postoperatively. Radiographs show a well-fixed implant. A MARS MRI reveals a large cystic lesion.

What is the classic histologic finding associated with this specific complication?

. Abundant neutrophils and gram-positive cocci
. Sheets of macrophages containing birefringent polyethylene debris
. Perivascular lymphocytic infiltrate and extensive tissue necrosis
. Benign neoplastic proliferation of synovial cells
. Multinucleated giant cell reaction to methylmethacrylate

Correct Answer & Explanation

. Abundant neutrophils and gram-positive cocci

Explanation

The clinical scenario and imaging describe an ALVAL (aseptic lymphocyte-dominated vasculitis-associated lesion) or pseudotumor, which is an adverse local tissue reaction to metal debris in metal-on-metal hips. Histologically, it represents a Type IV delayed hypersensitivity reaction characterized by perivascular lymphocytic infiltration and necrosis.

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