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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 16 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 301

Topic: Total Hip Arthroplasty (THA)

Digital templating was performed using a calibrated AP pelvis radiograph. The goals for acetabular component placement included maximizing coverage (80-90%), achieving appropriate inclination (40-45°) and anteversion (15-20°). For the femoral component, templating aimed to restore femoral offset, leg length, and potential for restoration of femoral anteversion. The lesser trochanter was used as a key landmark for stem depth and leg length adjustments.

Which of the following biomechanical parameters, when optimally restored during THA, is most critical for improving abductor muscle efficiency and minimizing the risk of a post-operative Trendelenburg gait?

. Acetabular component inclination of 40-45 degrees.
. Restoration of femoral offset.
. Achieving 15-20 degrees of acetabular anteversion.
. Using a 36mm femoral head diameter.
. Ensuring a 10-20 degree femoral stem anteversion.

Correct Answer & Explanation

. Restoration of femoral offset.

Explanation

Correct Answer: BRestoration of femoral offset is most critical for optimizing abductor muscle efficiency and minimizing the risk of a post-operative Trendelenburg gait. Femoral offset refers to the horizontal distance from the center of rotation of the femoral head to the long axis of the femur. Increasing the offset lengthens the abductor lever arm, allowing the gluteus medius and minimus muscles to generate more torque with less force, thereby improving their efficiency and reducing the likelihood of abductor insufficiency (Trendelenburg gait). While acetabular inclination (A) and anteversion (C) are crucial for stability and wear, and femoral stem anteversion (E) is important for preventing impingement and dislocation, they do not directly impact the abductor lever arm as significantly as femoral offset. Femoral head diameter (D) primarily influences range of motion and jump distance for stability, but not directly abductor mechanics.

Question 302

Topic: 3. Adult Reconstruction (Hip & Knee)

Pre-operative planning included assessing the femoral canal morphology. The patient's radiographs suggested a Dorr Type B femur, characterized by good metaphyseal-diaphyseal flare and adequate cortical thickness.

This specific femoral morphology (Dorr Type B) is generally considered most favorable for which type of femoral stem fixation in primary Total Hip Arthroplasty?

. Fully cemented stem, relying on a cement mantle for stability.
. Hybrid cemented stem, with a cemented femoral component and uncemented acetabular component.
. Fully uncemented stem, relying on press-fit and bone ingrowth.
. Femoral resurfacing arthroplasty, preserving more femoral bone.
. Custom-made stem, designed for highly complex anatomies.

Correct Answer & Explanation

. Fully uncemented stem, relying on press-fit and bone ingrowth.

Explanation

Correct Answer: CA Dorr Type B femur, characterized by good metaphyseal-diaphyseal flare and adequate cortical thickness, provides excellent bone stock for achieving primary press-fit stability. This morphology is considered ideal for a fully uncemented (cementless) femoral stem. Uncemented stems rely on this initial mechanical stability (press-fit) and subsequent biological fixation through bone ingrowth into a porous coating. Dorr Type A femurs (champagne flute, thick cortex, narrow canal) are at higher risk of fracture with uncemented stems and may sometimes benefit from cemented stems. Dorr Type C femurs (stovepipe, thin cortex, wide canal) often lack sufficient metaphyseal bone for press-fit and are typically better suited for cemented stems or specific uncemented designs that achieve diaphyseal fixation. Cemented stems (A, B) are generally preferred in osteoporotic bone or in cases where primary press-fit cannot be reliably achieved. Resurfacing arthroplasty (D) is a bone-preserving option for younger, active patients with good bone quality, but not directly related to the Dorr classification for stem fixation. Custom-made stems (E) are reserved for severe deformities or bone loss, not typically a standard Dorr Type B femur.

Question 303

Topic: 3. Adult Reconstruction (Hip & Knee)

The planned surgical approach for this patient's uncemented Total Hip Arthroplasty was a posterior (Kocher-Langenbeck) approach. During the procedure, the short external rotators (piriformis, gemelli, obturator internus) were identified, tenotomized close to their femoral insertion, and tagged with non-absorbable sutures. The posterior hip capsule was also incised and tagged.

At the time of closure, meticulous repair of which of the following structures is most crucial for enhancing post-operative stability and significantly reducing the risk of posterior dislocation, a known complication of this approach?

. The gluteus medius tendon.
. The iliopsoas tendon.
. The rectus femoris tendon.
. The short external rotators and posterior capsule.
. The vastus lateralis fascia.

Correct Answer & Explanation

. The short external rotators and posterior capsule.

Explanation

Correct Answer: DIn a posterior approach to the hip, the short external rotators (piriformis, gemelli, obturator internus) and the posterior capsule are incised to gain access to the hip joint. Meticulous repair of these structures at the time of closure is paramount for enhancing post-operative stability and significantly reducing the risk of posterior dislocation. This repair helps to restore the natural soft tissue restraints against posterior dislocation. The gluteus medius (A) is typically split or retracted, but its primary role is abduction, and its repair is not as directly linked to posterior stability as the rotators and capsule. The iliopsoas (B) and rectus femoris (C) are anterior structures and are not typically violated in a posterior approach. The vastus lateralis fascia (E) is part of the quadriceps mechanism and not directly involved in hip joint stability in this context.

Question 304

Topic: Total Hip Arthroplasty (THA)

Following an uncemented Total Hip Arthroplasty performed via a posterior approach, the patient is initiated on a post-operative rehabilitation protocol. This protocol includes immediate weight-bearing as tolerated with an assistive device and specific hip precautions.

Which of the following activities should the patient be most strictly instructed to avoid in the immediate post-operative period to minimize the risk of dislocation?

. Immediate weight-bearing as tolerated with a walker.
. Gentle hip abduction exercises in supine.
. Sleeping on the operative side with a pillow between the legs.
. Hip flexion beyond 90 degrees combined with adduction and internal rotation.
. Stationary cycling with appropriate seat height.

Correct Answer & Explanation

. Hip flexion beyond 90 degrees combined with adduction and internal rotation.

Explanation

Correct Answer: DFor a patient who has undergone THA via a posterior approach, the combination of hip flexion beyond 90 degrees, adduction past midline, and internal rotation is the classic position that places the hip at highest risk for posterior dislocation. Therefore, patients are strictly instructed to avoid this combination of movements in the immediate post-operative period. Immediate weight-bearing as tolerated (A) is standard for uncemented components. Gentle hip abduction exercises (B) are encouraged to strengthen abductors. Sleeping on the operative side with a pillow between the legs (C) is often recommended to maintain abduction and prevent adduction. Stationary cycling (E) is a low-impact exercise that can be introduced in early rehabilitation, provided the seat height is adjusted to prevent excessive hip flexion.

Question 305

Topic: 3. Adult Reconstruction (Hip & Knee)

The patient's X-rays showed classic features of severe osteoarthritis, making advanced imaging unnecessary. However, the case notes that a CT scan would be indicated for complex acetabular or femoral deformity, previous trauma, significant bone loss, or for detailed surgical planning for revision arthroplasty.

If the patient's symptoms were highly suggestive of a hip pathology but initial X-rays were equivocal or normal, an MRI scan would be most indicated to rule out which of the following conditions?

. Severe acetabular retroversion.
. Significant femoral anteversion.
. Avascular necrosis (AVN) of the femoral head.
. Extensive heterotopic ossification (HO).
. Periprosthetic joint infection (PJI).

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head.

Explanation

Correct Answer: CAn MRI scan is considered the diagnostic gold standard for avascular necrosis (AVN) of the femoral head, especially in early stages where X-ray findings may be equivocal or normal. MRI can detect marrow edema, serpentine low signal lines, and characteristic T1/T2 signal changes indicative of AVN before subchondral collapse or other radiographic signs become apparent. Severe acetabular retroversion (A) and significant femoral anteversion (B) are bony deformities best assessed by CT scan, which provides superior bony detail and 3D reconstruction. Extensive heterotopic ossification (D) is typically visible on X-rays, and CT can provide more detail, but MRI is not the primary modality for its diagnosis. Periprosthetic joint infection (E) is diagnosed based on clinical signs, lab markers (ESR, CRP, leukocyte count), aspiration, and sometimes nuclear imaging, with MRI having limited specific utility for PJI diagnosis due to artifact from metal implants.

Question 306

Topic: 3. Adult Reconstruction (Hip & Knee)

An 82-year-old female with severe osteoporosis sustains a highly comminuted both column acetabular fracture after a low-energy fall, as shown in the image. She is otherwise medically stable and ambulates independently with a cane. Considering the patient's age, bone quality, and fracture pattern, which of the following treatment strategies might be considered as a primary option, as discussed in the case, despite the general preference for open reduction and internal fixation (ORIF) in younger patients?

. Non-operative management with prolonged bed rest
. Open reduction and internal fixation with standard plates
. Primary total hip arthroplasty
. External fixation
. Arthrodesis

Correct Answer & Explanation

. Primary total hip arthroplasty

Explanation

Correct Answer: CThe correct answer isPrimary total hip arthroplasty (THA). The 'Summary of Key Literature / Guidelines' section, under 'Management in the Elderly,' states: 'Acetabular fractures in osteoporotic elderly patients present unique challenges. While anatomical reduction and fixation are still desirable, bone quality can make fixation tenuous. Debates continue regarding the role of primary total hip arthroplasty (THA) in severely comminuted or multi-column fractures in this population, as it may offer earlier mobilization and potentially better functional outcomes in selected cases, despite being a more extensive procedure.' Given the patient's advanced age, severe osteoporosis, and a highly comminuted both column fracture, primary THA is a recognized alternative to ORIF, which might be challenging to achieve stable fixation in poor bone quality. Non-operative management with prolonged bed rest is generally associated with high morbidity in the elderly. External fixation is typically for pelvic ring injuries or temporary stabilization, not definitive acetabular fixation. Arthrodesis is rarely performed and generally offers poorer quality of life.

Question 307

Topic: Total Hip Arthroplasty (THA)

A 48-year-old male undergoes open reduction for a complex posterior hip dislocation with an incarcerated osteochondral fragment. During the posterior approach, the surgeon is meticulously identifying and protecting structures to minimize the risk of iatrogenic injury and preserve femoral head vascularity. Which of the following arteries is considered the primary blood supply to the adult femoral head and is most vulnerable in this injury?

. Obturator artery (via ligamentum teres)
. Superior gluteal artery
. Medial circumflex femoral artery
. Lateral circumflex femoral artery
. Inferior gluteal artery

Correct Answer & Explanation

. Medial circumflex femoral artery

Explanation

Correct Answer: CThe case highlights the "Medial Circumflex Femoral Artery (MCFA): The primary blood supply to the femoral head in adults, ascending posteriorly and superiorly along the posterior aspect of the femoral neck, deep to the quadratus femoris and obturator externus. Damage to this artery, particularly its retinacular branches, is the main etiology of femoral head AVN following dislocation." The obturator artery via the ligamentum teres provides minimal blood supply in adults. The superior and inferior gluteal arteries supply the gluteal muscles and surrounding structures, while the lateral circumflex femoral artery primarily supplies the greater trochanter and vastus lateralis, not the femoral head itself.

Question 308

Topic: 3. Adult Reconstruction (Hip & Knee)

A 42-year-old male presents with a posterior hip dislocation and an associated femoral head fracture, classified as Pipkin Type II. After initial closed reduction, a post-reduction CT scan confirms the femoral head fragment is displaced and involves the weight-bearing superior aspect of the femoral head. What is the most appropriate definitive management for this injury?

. Non-weight-bearing for 6 weeks, followed by progressive weight-bearing.
. Immediate total hip arthroplasty due to high AVN risk.
. Excision of the femoral head fragment if it is small.
. Anatomical reduction and stable internal fixation of the femoral head fragment.
. Continuous passive motion (CPM) for 3 months to prevent stiffness.

Correct Answer & Explanation

. Anatomical reduction and stable internal fixation of the femoral head fragment.

Explanation

Correct Answer: DThe case outlines the management of Pipkin fractures: "Pipkin Type I (below fovea) and Type II (above fovea):Require anatomical reduction and stable internal fixation (typically headless compression screws). Excision of small, non-weight-bearing fragments may be considered." Given that the fragment is displaced and involves the weight-bearing superior aspect of the femoral head, anatomical reduction and stable internal fixation are crucial to restore articular congruity and prevent post-traumatic arthritis. Excision is typically reserved for very small, non-weight-bearing fragments. THA is generally reserved for end-stage arthritis or advanced AVN, not as an immediate treatment for an acute Pipkin Type II fracture in a 42-year-old.

Question 309

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old active male underwent total hip arthroplasty with a ceramic-on-ceramic bearing surface two years ago. He presents complaining of an audible squeaking sound from his hip when walking. What component malpositioning is most commonly associated with this phenomenon?

. Excessive acetabular anteversion and high inclination
. Retroverted femoral stem
. Varus placement of the femoral stem
. Decreased acetabular inclination
. Excessive femoral offset

Correct Answer & Explanation

. Excessive acetabular anteversion and high inclination

Explanation

Squeaking in ceramic-on-ceramic THA is frequently caused by edge loading of the bearing surfaces. This edge loading is typically secondary to cup malposition, specifically excessive inclination (a steep cup) and excessive anteversion, which leads to stripe wear.

Question 310

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male presents with a painful total hip arthroplasty 3 years post-surgery. Serum CRP is 15 mg/L and ESR is 45 mm/hr. Hip aspiration yields a synovial WBC count of 2,500 cells/uL with 75% neutrophils. Which of the following synovial fluid biomarkers provides the highest specificity for confirming a periprosthetic joint infection (PJI)?

. Interleukin-6 (IL-6)
. Alpha-defensin
. C-reactive protein (CRP)
. Leukocyte esterase
. Matrix metalloproteinase-9 (MMP-9)

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. It has been shown to be a highly specific and sensitive synovial fluid biomarker for diagnosing periprosthetic joint infection, particularly in cases with borderline traditional inflammatory markers.

Question 311

Topic: 3. Adult Reconstruction (Hip & Knee)

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

. Decrease the abductor moment arm
. Increase the overall joint reactive force
. Decrease the required force of the abductor musculature
. Decrease the varus bending moment on the femoral stem
. Increase the risk of anterior dislocation

Correct Answer & Explanation

. Decrease the required force of the abductor musculature

Explanation

Increasing femoral offset lengthens the abductor moment arm, which subsequently decreases the necessary abductor muscle force required to level the pelvis. This effectively decreases the overall joint reactive force but increases the varus torque on the stem.

Question 312

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with groin pain 5 years after an uncomplicated metal-on-crosslinked polyethylene total hip arthroplasty. Workup reveals a sterile pseudotumor. Which design factor is most strongly associated with mechanically assisted crevice corrosion at the head-neck junction?

. Large femoral head diameter (>36 mm)
. Use of a ceramic femoral head
. Low-offset neck geometry
. Titanium-alloy head on a titanium-alloy stem
. Small femoral head diameter (<28 mm)

Correct Answer & Explanation

. Large femoral head diameter (>36 mm)

Explanation

Large diameter metal heads (>36 mm) increase the frictional torque at the modular head-neck junction. This leads to micromotion, trunnion wear, and mechanically assisted crevice corrosion, potentially causing an adverse local tissue reaction (ALTR).

Question 313

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old male with a ceramic-on-ceramic total hip arthroplasty complains of an audible squeaking sound during hip flexion. Which of the following factors most strongly contributes to this phenomenon?

. Component malpositioning leading to edge loading
. Polyethylene wear debris
. Metal ion release causing metallosis
. Impingement of the greater trochanter on the ilium
. Aseptic loosening of the femoral stem

Correct Answer & Explanation

. Component malpositioning leading to edge loading

Explanation

Squeaking in ceramic-on-ceramic hips is primarily associated with component malpositioning (e.g., steep acetabular cup inclination or excessive version), which leads to loss of fluid film lubrication and subsequent edge loading and stripe wear.

Question 314

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female presents with a periprosthetic femur fracture around a cemented total hip arthroplasty. Radiographs show a fracture at the stem tip, a loose femoral component, but adequate distal diaphyseal bone stock. Based on the Vancouver classification, what is the most appropriate definitive management?

. Open reduction and internal fixation with a lateral locked plate
. Revision to a long uncemented extensively porous-coated stem
. Revision to a proximal femoral replacement
. Revision to a cemented standard length stem
. Nonoperative management with a hip spica cast

Correct Answer & Explanation

. Revision to a long uncemented extensively porous-coated stem

Explanation

This is a Vancouver B2 periprosthetic fracture, characterized by a fracture around the stem with a loose implant but adequate bone stock. The standard of care is revision arthroplasty using a long, uncemented diaphyseal-fitting stem that bypasses the fracture.

Question 315

Topic: 3. Adult Reconstruction (Hip & Knee)

In a patient undergoing revision total hip arthroplasty for recurrent instability, a dual mobility construct is selected. Which of the following best describes its primary biomechanical advantage in preventing dislocation?

. It provides a constrained, locking mechanism for the femoral head
. It significantly increases the resting tension of the abductor musculature
. It increases the effective functional jump distance and head-to-neck ratio
. It shifts the anatomical center of rotation superiorly and laterally
. It forces the use of a smaller effective head size to minimize impingement

Correct Answer & Explanation

. It increases the effective functional jump distance and head-to-neck ratio

Explanation

Dual mobility components utilize a smaller inner head articulated within a large mobile polyethylene liner. This design maximizes the effective head size, thereby significantly increasing the functional jump distance and head-to-neck ratio, effectively reducing dislocation risk.

Question 316

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male presents with groin pain 15 years after a primary total hip arthroplasty. Radiographs demonstrate significant eccentric wear of the polyethylene liner and large osteolytic lesions around the acetabular component. Which cell type is primarily responsible for initiating the biologic cascade that leads to this osteolysis?

. Osteoblasts
. T-lymphocytes
. Macrophages
. Neutrophils
. Osteocytes

Correct Answer & Explanation

. Macrophages

Explanation

Macrophages phagocytose polyethylene wear debris, initiating a foreign-body inflammatory response. They release cytokines such as TNF-alpha, IL-1, and IL-6, which subsequently stimulate osteoclast-mediated bone resorption.

Question 317

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old male presents after a mechanical fall with a periprosthetic femur fracture around a cemented total hip arthroplasty stem placed 10 years ago. Radiographs demonstrate a fracture at the tip of the stem. The stem is radiographically loose with subsidence, but there is adequate proximal femoral bone stock. According to the Vancouver classification, what is the most appropriate surgical management?

. Open reduction internal fixation with cables and locking plate
. Revision to a fully porous-coated long stem
. Revision with a proximal femoral replacement
. Nonoperative management in a spica cast
. Open reduction internal fixation with cortical strut allografts

Correct Answer & Explanation

. Revision to a fully porous-coated long stem

Explanation

This is a Vancouver B2 fracture (fracture around the stem, loose stem, adequate bone stock). The standard of care for B2 fractures is revision to a longer stem that bypasses the fracture, typically using a fully porous-coated or fluted tapered modular stem.

Question 318

Topic: Total Hip Arthroplasty (THA)

During preoperative templating for a total hip arthroplasty, the surgeon plans to use a high-offset femoral stem. Compared to a standard offset stem, what is the primary biomechanical advantage of increasing the femoral offset without changing the leg length?

. Increases the joint reaction force across the hip
. Decreases the tension on the iliotibial band
. Increases the abductor moment arm
. Increases the risk of bony impingement
. Decreases passive external rotation

Correct Answer & Explanation

. Increases the abductor moment arm

Explanation

Increasing femoral offset increases the abductor moment arm, which improves abductor muscle efficiency and decreases the overall joint reaction force. This enhances joint stability and helps prevent a Trendelenburg gait.

Question 319

Topic: 3. Adult Reconstruction (Hip & Knee)

A 40-year-old male who underwent a total hip arthroplasty 2 years ago reports excellent range of motion and no pain, but complains of a high-pitched, audible "squeaking" sound from his hip when bending or walking. Which bearing surface combination is most classically associated with this phenomenon?

. Metal-on-polyethylene
. Ceramic-on-polyethylene
. Metal-on-metal
. Ceramic-on-ceramic
. Oxinium-on-polyethylene

Correct Answer & Explanation

. Ceramic-on-ceramic

Explanation

Squeaking is a well-documented complication unique to ceramic-on-ceramic total hip arthroplasty bearings. It is thought to result from edge loading, microseparation, or stripe wear, leading to resonance within the component materials.

Question 320

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female is 5 years post-primary total hip arthroplasty using a large-diameter metal head on a titanium stem. She presents with persistent groin pain. MRI reveals a large, cystic pseudotumor. Inflammatory markers are normal and joint aspiration is negative for infection. Her presentation is most likely secondary to mechanically assisted crevice corrosion occurring at which interface?

. Head-liner interface
. Cup-bone interface
. Head-neck (trunnion) interface
. Stem-cement interface
. Liner-shell interface

Correct Answer & Explanation

. Head-neck (trunnion) interface

Explanation

Adverse local tissue reactions (ALTR) or pseudotumors in metal-on-polyethylene THA with large metal heads are typically caused by trunnionosis. This is mechanically assisted crevice corrosion at the modular head-neck (trunnion) junction.

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