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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 37 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 721

Topic: Total Knee Arthroplasty (TKA)

A 25-year-old patient requires a distal femoral osteotomy for a severe valgus deformity. Preoperative planning indicates that the Center of Rotation of Angulation (CORA) is located very close to the knee joint line, making an osteotomy at this precise location technically challenging and potentially compromising joint integrity. The surgeon decides to perform the osteotomy slightly proximal to the CORA, while still ensuring the hinge axis of the temporary external fixator passes through the CORA. According to Paley's Three Laws of Osteotomy, what is the expected outcome of this approach?

. Pure angular correction without any translation.
. Angulation with intentional translation, but correct mechanical axis alignment.
. Iatrogenic translation deformity with misaligned mechanical axes.
. Significant limb lengthening due to the proximal osteotomy.
. Significant limb shortening due to the proximal osteotomy.

Correct Answer & Explanation

. Angulation with intentional translation, but correct mechanical axis alignment.

Explanation

Correct Answer: BThis scenario describes Paley's Osteotomy Rule Two: 'When the hinge axis passes through the CORA, but the osteotomy is performed at a different level (proximal or distal to the CORA), the correction results in angulation plus translation.' The mechanical axes will still align correctly at the end of the procedure, but the bone ends at the actual osteotomy site will be offset (displaced). This rule is a powerful tool when the CORA is in an undesirable location, allowing the surgeon to achieve overall mechanical alignment while accepting an intentional offset at the osteotomy site.Option A is incorrect:Pure angular correction (Rule One) occurs only when both the osteotomy and the hinge axis pass directly through the CORA.Option C is incorrect:Iatrogenic translation deformity (Rule Three) occurs when both the hinge axis and the osteotomy are separate from the CORA, leading to misaligned mechanical axes. In this case, the hinge axis still passes through the CORA, ensuring mechanical axis alignment.Options D and E are incorrect:While some minor length changes can occur, the primary outcome described by Rule Two is angulation with translation, not significant lengthening or shortening as the main feature.

Question 722

Topic: Total Hip Arthroplasty (THA)

A 50-year-old patient presents with a long-standing knee flexion deformity. During gait analysis, it is noted that the patient exhibits a significant functional leg length discrepancy, with the pelvis dropping on the affected side during stance. This finding is most consistent with which of the following?

. A mild knee flexion deformity (5-15 degrees) with effective ankle dorsiflexion.
. A primary ankle equinus deformity without knee involvement.
. A severe knee flexion deformity (>20 degrees) overwhelming distal compensation.
. A fixed hip flexion contracture as the primary pathology.
. A posterior shift of the Ground Reaction Vector (GRV) anterior to the knee.

Correct Answer & Explanation

. A severe knee flexion deformity (>20 degrees) overwhelming distal compensation.

Explanation

Correct Answer: CThe case states that when the FFD exceeds 20-25°, the body's ability to compensate distally is overwhelmed. This leads to a rapid cascade of more severe gait abnormalities, including afunctional leg length discrepancy. The flexed posture functionally shortens the limb's vertical height, causing the pelvis to drop on the affected side during stance, leading to a shortened step length on the contralateral side and a noticeable limp. This is a hallmark of severe, uncompensated FFD.Option A is incorrect. Mild FFDs are typically compensated by ankle dorsiflexion and hip flexion/trunk lean, and while they cause some gait changes, a significant functional leg length discrepancy with pelvic drop is characteristic of more severe deformities.Option B is incorrect. While an ankle equinus deformity can contribute to gait issues, the question specifically points to a knee flexion deformity causing the functional leg length discrepancy and pelvic drop.Option D is incorrect. While a fixed hip flexion contracture can cause a functional leg length discrepancy, the question specifies akneeflexion deformity as the primary issue leading to this gait pattern.Option E is incorrect. In FFD, the GRV shiftsposteriorto the knee, creating a flexion moment, not anterior.

Question 723

Topic: Total Knee Arthroplasty (TKA)

A 50-year-old patient undergoes a distal femoral extension osteotomy to correct a significant procurvatum deformity. Postoperatively, the patient's mechanical alignment is restored, but they complain of a new-onset, significant limitation in knee flexion. What is the primary biomechanical reason for this?

. The osteotomy moved the functional arc of motion entirely into extension
. Iatrogenic patella alta reduced quadriceps efficiency
. The patellofemoral joint pressure was abnormally reduced
. The posterior cruciate ligament was inadvertently lengthened
. A sympathetic reflex arc inhibited the hamstring muscles

Correct Answer & Explanation

. The osteotomy moved the functional arc of motion entirely into extension

Explanation

Correcting a procurvatum deformity via an extension osteotomy shifts the entire arc of motion towards extension. If the patient had adapted their soft tissues to the flexed position, this shift typically reduces maximum terminal flexion postoperatively.

Question 724

Topic: Total Hip Arthroplasty (THA)

A surgeon corrects a proximal tibial procurvatum deformity. Both the osteotomy and the hinge are inadvertently placed 3 cm distal to the true CORA. According to Paley's Rule 3, what is the mechanical consequence of this execution?

. Pure angulation with collinear mechanical axes
. Overcorrection of the joint line orientation
. The proximal and distal mechanical axes will be parallel but translated
. An apex posterior secondary deformity will be induced
. The osteotomy will result in a leg length discrepancy but perfect alignment

Correct Answer & Explanation

. The proximal and distal mechanical axes will be parallel but translated

Explanation

Paley's Rule 3 dictates that if both the osteotomy and the hinge are located away from the CORA, the resulting mechanical axes will be parallel to each other but translated, creating a secondary translation deformity.

Question 725

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with cerebral palsy presents with severe bilateral knee flexion posturing during gait. Sagittal radiographs show an mPDFA of 83 degrees and an mPPTA of 81 degrees. The popliteal angle is 70 degrees. What is the most appropriate initial management strategy?

. Distal femoral extension osteotomy
. Proximal tibial flexion osteotomy
. Soft tissue hamstring lengthening and capsular release
. Femoral shortening osteotomy
. Total knee arthroplasty

Correct Answer & Explanation

. Soft tissue hamstring lengthening and capsular release

Explanation

Normal mPDFA and mPPTA values indicate the bony architecture is normal. The knee flexion is due to soft tissue contracture (hamstring spasticity), making soft tissue lengthening the appropriate initial management rather than bony osteotomy.

Question 726

Topic: Total Hip Arthroplasty (THA)

When planning an anterior closing wedge osteotomy of the distal femur to correct a symptomatic procurvatum deformity, the surgeon must counsel the patient on which inherent consequence of this specific osteotomy technique?

. Limb lengthening
. Limb shortening
. Increased patellofemoral tracking instability
. Obligatory posterior translation of the mechanical axis
. Iatrogenic patella alta

Correct Answer & Explanation

. Limb shortening

Explanation

A closing wedge osteotomy removes a segment of bone, inherently resulting in some degree of limb shortening. This must be factored into preoperative planning, especially if a leg length discrepancy already exists.

Question 727

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old patient presents with a chronically unstable, painful right hip following a Girdlestone resection arthroplasty performed 15 years prior for a periprosthetic infection. He ambulates with a severe Trendelenburg gait and significant limb shortening. He is not a candidate for revision total hip arthroplasty due to persistent infection markers and extensive bone loss. Based on the provided case material, which of the following is the most appropriate surgical intervention?

. Hip arthrodesis.
. Revision total hip arthroplasty with a custom implant.
. Pelvic Support Osteotomy (PSO).
. Proximal femoral shortening osteotomy.
. Non-operative management with bracing and crutches.

Correct Answer & Explanation

. Pelvic Support Osteotomy (PSO).

Explanation

Correct Answer: CThe case explicitly lists 'Girdlestone Arthroplasty Salvage' as a primary surgical indication for the Pelvic Support Osteotomy (PSO). It states that following resection for intractable infection or massive bone loss, patients may be unsuitable candidates for revision THA, and PSO offers a stable, durable reconstruction without implants, which is ideal in the setting of chronic infection. Hip arthrodesis (A) is a salvage option but often less desirable than a mobile, stable hip. Revision THA (B) is contraindicated due to persistent infection and bone loss. Proximal femoral shortening (D) would worsen limb length discrepancy and not address instability. Non-operative management (E) would not resolve the instability, pain, or functional limitations.

Question 728

Topic: 3. Adult Reconstruction (Hip & Knee)

A 40-year-old female presents with a severe, fixed hip adduction contracture and an apparent leg length discrepancy (LLD) of 6 cm. A full-length scanogram confirms that the osseous lengths of both femurs and tibias are equal. The patient experiences significant gait disturbance and compensatory lumbar scoliosis. What is the most appropriate surgical strategy to address this patient's condition according to Paley's principles?

. Perform a femoral lengthening procedure to correct the 6 cm LLD.
. Perform a contralateral epiphysiodesis to shorten the longer limb.
. Perform a varus-producing osteotomy at the proximal femur to further adduct the hip.
. Perform an opening wedge valgus-producing osteotomy at the CORA of the proximal femur.
. Proceed directly to total hip arthroplasty to restore hip mechanics.

Correct Answer & Explanation

. Perform an opening wedge valgus-producing osteotomy at the CORA of the proximal femur.

Explanation

Correct Answer: DThe case explicitly warns against treating an apparent LLD with a lengthening procedure: 'Attempting to treat an apparent LLD with a femoral lengthening procedure is a grave biomechanical error.' It states that 'When planning the correction of a varus or adduction deformity that is causing an apparent LLD, the surgical goal isnotlengthening. The goal is to perform a valgus-producing osteotomy at the CORA.' An opening wedge valgus osteotomy is particularly powerful as it 'corrects the angular deformity, realigning the mechanical axis to be perpendicular to the pelvis. This levels the pelvis and instantly eliminates the apparent LLD.' Options A and B are incorrect as they address true LLD, which is not present here. Option C would exacerbate the adduction deformity. Option E might be considered for severe arthritis, but the primary issue described is a fixed contracture and apparent LLD, which is amenable to osteotomy.

Question 729

Topic: Total Hip Arthroplasty (THA)

The right panel of the provided image shows the final radiograph of the patient after fixator removal and bony consolidation following a proximal femoral osteotomy for a severe adduction deformity. What key biomechanical outcome is demonstrated in this final radiograph, indicating successful correction according to Paley's principles?

. Persistent pelvic obliquity and an apparent leg length discrepancy.
. Creation of an iatrogenic translational deformity (MAD).
. A perfectly level pelvis and a straight, collinear mechanical axis.
. Increased varus malalignment of the proximal femur.
. A significant increase in true leg length discrepancy.

Correct Answer & Explanation

. A perfectly level pelvis and a straight, collinear mechanical axis.

Explanation

Correct Answer: CThe caption for the image explicitly states that the 'Right Panel: The final radiograph after fixator removal and bony consolidation shows a perfectly level pelvis and a straight, collinear mechanical axis, demonstrating the successful restoration of overall limb alignment and functional leg length.' This directly reflects the ultimate goal of Paley's deformity correction system, where the PMA and DMA become perfectly collinear and perpendicular to a level pelvic horizontal line. Options A, B, D, and E describe outcomes of failed or incomplete correction, which are clearly contradicted by the image and its description.

Question 730

Topic: Total Hip Arthroplasty (THA)

A 40-year-old patient presents with a proximal femoral deformity where the CORA is located deep within the femoral neck, an anatomically challenging and potentially avascular region. The surgeon decides to perform the osteotomy at a more practical and healthy level in the intertrochanteric region, while ensuring the axis of correction (hinge) still passes through the original CORA. Which of Paley's osteotomy rules is being applied, and what is its primary implication?

. Rule 1; it will result in pure angular correction with zero translation.
. Rule 3; it will create an unintentional secondary translation deformity.
. Rule 2; it will result in a calculated, necessary translation simultaneously with the angular correction.
. Rule 1; it is a planning error and should be avoided.
. Rule 2; it will only correct the leg length discrepancy, not the angulation.

Correct Answer & Explanation

. Rule 2; it will result in a calculated, necessary translation simultaneously with the angular correction.

Explanation

Correct Answer: CThis scenario perfectly describes Paley's Osteotomy Rule 2: 'The osteotomy is at a different level than the CORA, but the axis of correction (hinge) still passes through the CORA.' The text states this is 'a highly powerful and frequently used technique in the hip' when the CORA is in an inaccessible or undesirable location. The primary implication is that 'the bone ends will undergo a calculated, necessary translation simultaneously with the angular correction. This translation is vital to perfectly realign the mechanical axis.'Option A is incorrectbecause Rule 1 applies when both the osteotomy and the hinge pass through the CORA, resulting in pure angular correction without translation.Option B is incorrectbecause Rule 3 describes a planning error where both the osteotomy and the hinge are away from the CORA, leading to unintentional translation.Option D is incorrectbecause Rule 1 is the ideal scenario for pure angular correction, not a planning error. The scenario described is Rule 2.Option E is incorrectbecause Rule 2 is designed for both angular and calculated translational correction to realign the mechanical axis, not solely for leg length discrepancy.

Question 731

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following represents a strict contraindication to performing a double-level pelvic support osteotomy (PSO) for chronic hip instability?

. Limb length discrepancy greater than 5 cm
. Ipsilateral severe knee stiffness or osteoarthritis
. Previous failed total hip arthroplasty with retained cement
. Bilateral high hip dislocations
. Complete absence of the femoral head and neck

Correct Answer & Explanation

. Ipsilateral severe knee stiffness or osteoarthritis

Explanation

A stable, painless, and mobile knee is an absolute prerequisite because the PSO alters the mechanical axis and places unique new biomechanical demands on the knee. Severe knee stiffness or preexisting advanced osteoarthritis is a contraindication.

Question 732

Topic: Total Hip Arthroplasty (THA)

According to the Paley multiplier method for predicting leg length discrepancy at skeletal maturity, which combination of variables is utilized to derive the correct multiplier?

. Current chronological age and height
. Bone age determined by Greulich and Pyle atlas and gender
. Chronological age and gender
. Current length of the normal limb and gender
. The exact etiology of the limb length discrepancy and age

Correct Answer & Explanation

. Chronological age and gender

Explanation

The Paley multiplier method relies on multiplying the current measurement by a coefficient that is specific to the patient's chronological age and gender. It rarely requires bone age calculations unless the child has an overtly abnormal skeletal growth syndrome.

Question 733

Topic: 3. Adult Reconstruction (Hip & Knee)

You are evaluating a patient with a chronically dislocated hip who underwent a historic single-level pelvic support osteotomy 15 years ago. They are complaining of progressive ipsilateral knee pain. Radiographs will most likely demonstrate which of the following?

. Varus knee osteoarthritis
. Valgus knee osteoarthritis
. Severe patella baja
. Recurvatum deformity of the proximal tibia
. Avascular necrosis of the medial femoral condyle

Correct Answer & Explanation

. Valgus knee osteoarthritis

Explanation

Historic single-level PSOs resulted in a massive lateral shift of the mechanical axis. Over time, this extreme mechanical deviation led to predictable valgus overload and subsequent valgus osteoarthritis of the knee.

Question 734

Topic: Total Hip Arthroplasty (THA)

A 24-year-old male is undergoing an Ilizarov hip reconstruction (double-level pelvic support osteotomy). What is the primary biomechanical purpose of the distal osteotomy in this procedure?

. To provide a fulcrum against the obturator foramen.
. To induce valgus to compensate for leg length discrepancy.
. To correct the lateral mechanical axis deviation and allow for limb lengthening.
. To correct persistent hip flexion contractures.
. To distalize the greater trochanter to restore abductor tension.

Correct Answer & Explanation

. To correct the lateral mechanical axis deviation and allow for limb lengthening.

Explanation

The proximal valgus osteotomy shifts the mechanical axis laterally, creating a significant lateral mechanical axis deviation (MAD). The distal varus osteotomy realigns the mechanical axis and serves as the site for lengthening to correct the limb length discrepancy.

Question 735

Topic: 3. Adult Reconstruction (Hip & Knee)

While evaluating candidates for a pelvic support osteotomy (PSO), which of the following clinical findings is considered an absolute contraindication to the procedure?

. Severe limb length discrepancy greater than 5 cm.
. Active infection in the ipsilateral hip joint.
. A stiff knee with less than 40 degrees of flexion.
. Absence of the femoral head and neck.
. Previous failed total hip arthroplasty.

Correct Answer & Explanation

. A stiff knee with less than 40 degrees of flexion.

Explanation

A stiff knee (typically less than 45-60 degrees of flexion) is a major contraindication to PSO. The valgus osteotomy restricts hip adduction and alters limb mechanics, making functional knee flexion critical for sitting and clearing the foot during the swing phase of gait.

Question 736

Topic: Total Hip Arthroplasty (THA)

Following a successful proximal valgus-extension osteotomy in an Ilizarov hip reconstruction, the surgeon must now plan the distal osteotomy. What are the two vital functions of this distal varus-lengthening osteotomy?

. A. To provide the critical buttress against the ischium and tension the slackened abductor musculature.
. B. To acutely correct the hip flexion contracture and eliminate compensatory lumbar lordosis.
. C. To act as the 're-centering' osteotomy to correct lateral Mechanical Axis Deviation (MAD) and serve as the site for gradual distraction osteogenesis to correct leg length discrepancy.
. D. To fuse the hip joint, providing definitive stability and pain relief.
. E. To prevent patellar instability and restore the Joint Line Congruency Angle (JLCA) to 0 degrees without affecting limb length.

Correct Answer & Explanation

. C. To act as the 're-centering' osteotomy to correct lateral Mechanical Axis Deviation (MAD) and serve as the site for gradual distraction osteogenesis to correct leg length discrepancy.

Explanation

Correct Answer: CThe case clearly outlines the functions of the distal osteotomy: 'A Distal Varus-Lengthening Osteotomy: This serves two vital functions. First, it acts as the 're-centering' osteotomy, correcting the lateral MAD created by the proximal cut and restoring a normal mLDFA. Second, it serves as the site for gradual distraction osteogenesis to correct the leg length discrepancy.'Option A is incorrectas these are the functions of theproximalvalgus-extension osteotomy.Option B is incorrectas these are also functions of theproximalextension osteotomy.Option D is incorrectas the modern standard of care aims to preserve a functional, mobile hip joint, not to fuse it.Option E is incorrectbecause while it helps prevent knee pathology, its primary functions are MAD correction and LLD correction, and it does affect limb length.

Question 737

Topic: Total Hip Arthroplasty (THA)

A newborn is noted to have a significant posteromedial bowing of the left tibia and a calcaneovalgus positioning of the left foot. What is the most expected natural history of this condition?

. Progressive angular deformity leading to pseudoarthrosis
. Spontaneous resolution of the angular deformity with progressive leg length discrepancy
. Development of anterolateral bowing by age 2
. Spontaneous resolution of both the bowing and leg length discrepancy
. High risk of associated neurofibromatosis type 1

Correct Answer & Explanation

. Spontaneous resolution of the angular deformity with progressive leg length discrepancy

Explanation

Posteromedial bowing of the tibia typically undergoes spontaneous remodeling and improvement of the angular deformity, but it invariably leaves the patient with a residual leg length discrepancy that requires monitoring.

Question 738

Topic: Total Hip Arthroplasty (THA)

A 6-year-old girl has a leg length discrepancy (LLD) secondary to a malunited femur fracture. Using the Paley multiplier method, how is the predicted LLD at skeletal maturity most accurately calculated?

. Current LLD divided by the chronologic age multiplier
. Current LLD multiplied by the skeletal age multiplier
. Current length of the normal limb multiplied by the chronologic age multiplier
. Predicted mature length of the normal limb minus the current LLD
. Current LLD multiplied by a gender-specific constant

Correct Answer & Explanation

. Current LLD multiplied by the skeletal age multiplier

Explanation

The Paley multiplier method predicts LLD at maturity by multiplying the current LLD by an age- and gender-specific multiplier. Skeletal age should be used if it deviates significantly from chronologic age.

Question 739

Topic: 3. Adult Reconstruction (Hip & Knee)

A 14-year-old boy presents with a severe Trendelenburg gait and a 5 cm leg length discrepancy (LLD) secondary to infantile septic arthritis of the hip. Radiographs reveal complete absence of the femoral head and neck with proximal migration of the femoral shaft. Which of the following procedures is best designed to simultaneously address his abductor lurch and LLD?

. Proximal femoral focal lengthening using a monolateral fixator
. Ilizarov pelvic support osteotomy with distal femoral lengthening
. Greater trochanteric arthroplasty with an adductor tenotomy
. Chiari pelvic osteotomy with shelf augmentation
. Cementless total hip arthroplasty with a subtrochanteric shortening osteotomy

Correct Answer & Explanation

. Ilizarov pelvic support osteotomy with distal femoral lengthening

Explanation

The Ilizarov pelvic support osteotomy consists of a proximal femoral valgus-extension osteotomy to eliminate the Trendelenburg gait, combined with a distal femoral osteotomy for lengthening and mechanical axis realignment. It is the gold standard for late reconstruction of Hunka Type V septic hip sequelae.

Question 740

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with an external fixator presents with erythema, localized pain, and minor serous discharge around a tibial half-pin. Radiographs show no evidence of pin loosening or osteolysis. According to the Checketts-burns classification, how should this be managed?

. Immediate pin removal and frame revision in the operating room
. Admission for intravenous antibiotics and surgical debridement
. Local pin site care and a short course of oral antibiotics
. Immediate amputation of the affected limb segment
. Injection of local corticosteroids into the pin tract

Correct Answer & Explanation

. Local pin site care and a short course of oral antibiotics

Explanation

Minor pin tract infections without osteolysis or pin loosening are classified as Checketts-burns Grades 1 and 2. They are appropriately managed conservatively with enhanced local pin care and oral antibiotics.

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