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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 40 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 781

Topic: Total Hip Arthroplasty (THA)

A junior resident plans a proximal tibial osteotomy for a varus deformity. By mistake, both the osteotomy and the center of the hinge are placed 5 cm proximal to the true CORA. According to Paley's principles, what is the geometric consequence of this technical error?

. Anatomic collinear correction of the mechanical axes.
. Collinear mechanical axes with translation at the osteotomy site.
. Parallel mechanical axes with an induced translation (zig-zag deformity).
. Overcorrection into valgus with joint line obliquity.
. Pure leg length discrepancy without angular change.

Correct Answer & Explanation

. Parallel mechanical axes with an induced translation (zig-zag deformity).

Explanation

Paley's Osteotomy Rule 3 states that if the hinge and osteotomy are placed at a level other than the CORA, the mechanical axes will become parallel rather than collinear. This induces a translation and creates a zig-zag deformity.

Question 782

Topic: Total Hip Arthroplasty (THA)

A patient presents with a multi-apical tibial deformity demonstrating two distinct CORAs. If the surgeon decides to correct the entire deformity using a single osteotomy at the proximal CORA, what compensatory action must be incorporated to achieve a collinear mechanical axis?

. Pure angular correction at the proximal CORA.
. Translation at the single osteotomy site.
. Overcorrection of the valgus angulation by 15 degrees.
. Placement of the ACA at the distal CORA.
. Creation of an intentional leg length discrepancy.

Correct Answer & Explanation

. Translation at the single osteotomy site.

Explanation

When a multi-apical deformity is corrected with a single osteotomy located at one of the CORAs, angular correction alone will leave a translation deformity. Translation must be purposefully added at the osteotomy site to restore collinearity of the overall mechanical axis.

Question 783

Topic: Total Hip Arthroplasty (THA)

A 28-year-old male is undergoing treatment for a 5 cm post-traumatic tibial leg length discrepancy using the Lengthening Over a Nail (LON) technique. What is the primary advantage of LON compared to classic distraction osteogenesis using solely a circular external fixator?

. It increases the bone healing index required for consolidation.
. It eliminates the risk of deep infection entirely.
. It significantly decreases the external fixation index (time spent in the frame).
. It allows for earlier weight-bearing without crutches.
. It negates the need for a corticotomy.

Correct Answer & Explanation

. It significantly decreases the external fixation index (time spent in the frame).

Explanation

The LON technique allows the external fixator to be removed immediately after the distraction phase is complete, once the nail is locked. This drastically reduces the time the patient must wear the external frame.

Question 784

Topic: Total Hip Arthroplasty (THA)

A 12-year-old girl has a leg length discrepancy. Using the Paley Multiplier Method to predict her leg length discrepancy at maturity, the surgeon multiplies her current discrepancy by an age-specific multiplier. What physiological event marks the stabilization of the multiplier at 1.0 (indicating skeletal maturity) for females in this system?

. Closure of the distal fibular physis
. Onset of menarche
. Chronological age of 16 years
. Chronological age of 18 years
. Risser stage 5

Correct Answer & Explanation

. Onset of menarche

Explanation

In the multiplier method for females, skeletal growth significantly tapers and the multiplier approaches 1.0 around skeletal maturity, which closely correlates with bone age following the onset of menarche.

Question 785

Topic: Total Hip Arthroplasty (THA)

If a surgeon attempts to correct a multi-apical diaphyseal deformity of the tibia by performing a single osteotomy at the intersection point of the proximal and distal mechanical axes (the apparent single CORA), what is the inevitable geometric result?

. Perfect restoration of the anatomic axis without any translation.
. Restoration of the overall mechanical axis, but creation of severe translation of the middle bone segment.
. Failure to restore the overall mechanical axis.
. Creation of an apex posterior recurvatum deformity.
. Leg length discrepancy exceeding 5 cm.

Correct Answer & Explanation

. Restoration of the overall mechanical axis, but creation of severe translation of the middle bone segment.

Explanation

When a multi-apical deformity is corrected with a single osteotomy at the overall mechanical axis intersection, the mechanical axis is restored, but the intervening segment undergoes severe, un-anatomic translation.

Question 786

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old patient with varus thrust has an MPTA of 84 degrees and a standing JLCA of 7 degrees (lateral opening). To successfully eliminate the varus thrust and restore dynamic stability, which surgical strategy is recommended?

. Under-correct the varus deformity to preserve lateral compartment cartilage
. Correct purely to a neutral mechanical axis (0 degrees)
. Overcorrect the mechanical axis into valgus to shift the ground reaction force laterally
. Perform an isolated lateral collateral ligament reconstruction without osteotomy
. Perform a medial unicompartmental knee arthroplasty

Correct Answer & Explanation

. Overcorrect the mechanical axis into valgus to shift the ground reaction force laterally

Explanation

In the presence of significant LCL laxity and varus thrust, overcorrecting the mechanical axis laterally ensures the knee adduction moment is neutralized during stance, dynamically tensioning the medial side and preventing lateral joint opening.

Question 787

Topic: Total Knee Arthroplasty (TKA)

A 45-year-old male is undergoing a high tibial osteotomy for a severe medial compartment osteoarthritis and varus deformity. Paley's analysis reveals a tibial deformity with the CORA located at the joint line. If a proximal tibial osteotomy is performed distal to the CORA (Paley's Rule 2) and corrected by angulation alone, what is the resulting mechanical alignment?

. The mechanical axes will be collinear, restoring normal joint loading.
. The mechanical axes will be parallel but translated, creating a zigzag deformity.
. The mechanical axis will shift excessively into the lateral compartment.
. The joint line obliquity will be completely corrected to 0 degrees.
. The medial proximal tibial angle (MPTA) will remain unchanged.

Correct Answer & Explanation

. The mechanical axes will be parallel but translated, creating a zigzag deformity.

Explanation

Paley's Osteotomy Rule 2 indicates that if an osteotomy is performed at a level different from the CORA and corrected by angulation alone, the proximal and distal mechanical axes will be parallel but translated. To make them collinear, translation at the osteotomy site must accompany the angulation (Rule 3).

Question 788

Topic: Total Knee Arthroplasty (TKA)

A 35-year-old male with chronic LCL laxity and a varus thrust undergoes a proximal tibial osteotomy. The surgeon aims to dynamically tension the deficient lateral structures by altering the mechanical axis. Which target mechanical alignment is most appropriate to eliminate the varus thrust in this patient?

. 0 degrees (neutral alignment with the MAD exactly through the center of the knee).
. 3 to 5 degrees of mechanical valgus (MAD lateral to the center of the knee).
. 2 degrees of mechanical varus (MAD slightly medial to the center of the knee).
. 10 degrees of mechanical valgus to fully offload the lateral compartment.
. Anatomic valgus of 5-7 degrees, corresponding to mechanical neutral.

Correct Answer & Explanation

. 3 to 5 degrees of mechanical valgus (MAD lateral to the center of the knee).

Explanation

In the presence of lateral collateral ligament (LCL) laxity and a varus thrust, overcorrecting the mechanical axis into 3 to 5 degrees of mechanical valgus forces the knee into a valgus position during stance. This tensions the lateral soft-tissue sleeve and dynamically eliminates the varus thrust.

Question 789

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the Paley Method, if a patient has a varus deformity characterized by a mechanical axis deviation (MAD) of 30 mm medial to the knee center, an mLDFA of 94 degrees, an MPTA of 87 degrees, and a JLCA of 1 degree, which procedure is most indicated to correct the alignment?

. Medial opening wedge high tibial osteotomy
. Lateral closing wedge distal femoral osteotomy
. Double-level osteotomy (femur and tibia)
. Lateral collateral ligament reconstruction
. Medial unicompartmental knee arthroplasty

Correct Answer & Explanation

. Lateral closing wedge distal femoral osteotomy

Explanation

The parameters indicate a purely femoral deformity: the mLDFA is abnormal (94 degrees, normal ~88), while the MPTA is normal (87 degrees) and the JLCA is normal (1 degree). Therefore, a distal femoral osteotomy (such as lateral closing wedge or medial opening wedge) is required.

Question 790

Topic: Total Knee Arthroplasty (TKA)

A 55-year-old male with medial unicompartmental osteoarthritis and a varus deformity is being evaluated for a High Tibial Osteotomy (HTO). Which of the following is considered an absolute contraindication to performing an isolated valgus-producing HTO?

. A joint line convergence angle (JLCA) of 3 degrees.
. A preoperative mechanical axis deviation (MAD) of 20 mm medial.
. Advanced full-thickness chondral loss in the lateral compartment.
. A medial proximal tibial angle (MPTA) of 84 degrees.
. A dynamic varus thrust during gait.

Correct Answer & Explanation

. Advanced full-thickness chondral loss in the lateral compartment.

Explanation

A valgus-producing HTO shifts the weight-bearing axis into the lateral compartment. Advanced lateral compartment osteoarthritis (full-thickness chondral loss) is an absolute contraindication, as the increased lateral loading will cause rapid symptom progression.

Question 791

Topic: 3. Adult Reconstruction (Hip & Knee)



A patient presents with a severe varus deformity. The mechanical axis deviation (MAD) is 50 mm medial to the center of the knee. The mechanical medial proximal tibial angle (mPTA) is 80 degrees, and the mechanical lateral distal femoral angle (mLDFA) is 96 degrees. The JLCA is normal. What is the most appropriate surgical intervention to correct the mechanical axis while avoiding excessive joint line obliquity?

. Isolated high tibial osteotomy (HTO)
. Isolated distal femoral osteotomy (DFO)
. Unicompartmental knee arthroplasty
. Double level osteotomy (femur and tibia)
. Lateral collateral ligament reconstruction

Correct Answer & Explanation

. Double level osteotomy (femur and tibia)

Explanation

Both the mPTA (normal 87 degrees) and mLDFA (normal 87 degrees) are significantly abnormal, indicating combined femoral and tibial deformity. Correcting this magnitude solely in one bone would result in unacceptable joint line obliquity, necessitating a double level osteotomy.

Question 792

Topic: 3. Adult Reconstruction (Hip & Knee)

A 30-year-old male presents with chronic posterolateral corner (PLC) and lateral collateral ligament (LCL) instability following a sports injury, accompanied by a 10-degree varus mechanical alignment. What is the most appropriate, biomechanically sound treatment strategy?

. Isolated LCL/PLC reconstruction
. Isolated distal femoral varus osteotomy
. High tibial osteotomy (HTO) prior to or concurrent with ligament reconstruction
. Unicompartmental knee arthroplasty
. Primary total knee arthroplasty

Correct Answer & Explanation

. High tibial osteotomy (HTO) prior to or concurrent with ligament reconstruction

Explanation

In the setting of combined varus malalignment and lateral-sided instability, the varus mechanical axis must be corrected (via HTO) to prevent excessive tensile forces from stretching out and failing a subsequent or concurrent LCL/PLC soft tissue reconstruction.

Question 793

Topic: Total Knee Arthroplasty (TKA)

According to Paley's principles, if an osteotomy is performed exactly at the Center of Rotation of Angulation (CORA) but the hinge (ACA) is placed eccentric to the CORA (Osteotomy Rule 1 variant), what will be the resulting mechanical alignment?

. Pure angular correction with collinear axes.
. Collinear axes but with length gain or loss.
. Parallel axes with translation.
. Secondary translational deformity.
. Torsional malalignment.

Correct Answer & Explanation

. Collinear axes but with length gain or loss.

Explanation

If the osteotomy is at the CORA but the ACA is eccentric to it (like placing a hinge on the cortex rather than the central axis), the mechanical axes remain collinear, but there is an intentional or consequential opening/closing wedge effect that alters the absolute length of the bone segment.

Question 794

Topic: 3. Adult Reconstruction (Hip & Knee)

A 28-year-old male competitive weightlifter complains of an aching right shoulder pain, exacerbated by bench pressing and cross-body adduction. Radiographs show subchondral cystic changes and widening of the AC joint. If conservative management fails, which of the following is the most appropriate surgical step?

. Coracoacromial ligament transfer (Weaver-Dunn)
. Distal clavicle excision of 1-2 cm
. Distal clavicle excision of 4-5 mm
. Subacromial decompression
. Open reduction and internal fixation

Correct Answer & Explanation

. Distal clavicle excision of 4-5 mm

Explanation

Distal clavicle osteolysis in weightlifters is managed conservatively first. If recalcitrant, excision of 4-5 mm of the distal clavicle is sufficient to relieve symptoms while avoiding iatrogenic AC instability.

Question 795

Topic: 3. Adult Reconstruction (Hip & Knee)

A 33-year-old laborer undergoes delayed surgical reconstruction of a Rockwood Type V AC joint injury that occurred 4 months ago. Why is a biologic graft (e.g., semitendinosus allograft) favored over isolated non-absorbable suture fixation for this chronic injury?

. Suture fixation causes immediate acromial osteolysis.
. The native CC ligaments lose their healing potential after 3-6 weeks.
. Biologic grafts do not require osseous tunnels.
. The AC joint requires rigid arthrodesis in chronic settings.
. Suture material is toxic to the coracoid periosteum.

Correct Answer & Explanation

. The native CC ligaments lose their healing potential after 3-6 weeks.

Explanation

In acute AC separations (<3-6 weeks), rigid fixation can allow the torn native ligaments to heal. In chronic cases, the ligaments undergo scarring and atrophy, losing healing potential, thereby requiring a biologic graft for long-term stability.

Question 796

Topic: 3. Adult Reconstruction (Hip & Knee)

A 30-year-old patient presents with a complex post-traumatic deformity of the distal tibia, requiring a closing wedge osteotomy. Preoperative templating indicates a 15-degree correction. The surgeon is aware of potential intraoperative inaccuracies. Which of the following factors, if not accounted for, could lead to an unintended overcorrection of the deformity?

. Insufficient preservation of the concave cortical hinge.
. Aggressive periosteal stripping on the convex side of the osteotomy.
. Failure to account for the kerf of the oscillating saw blade and the Krackow effect.
. Performing the osteotomy at a level different from the CORA without translation.
. Making the proximal and distal cuts of the bony wedge non-parallel.

Correct Answer & Explanation

. Failure to account for the kerf of the oscillating saw blade and the Krackow effect.

Explanation

Correct Answer: CThe case specifically highlights two factors that can lead to unintended overcorrection: 'Accounting for the Kerf: An oscillating saw blade does not simply magically part the bone; it physically vaporizes a strip of bone equal to the blade's thickness. ...When making two separate converging cuts for a closing wedge, the surgeon removes not only the planned wedge itself but also the width of two saw blade kerfs. ...This can easily translate to 1-2 degrees of unintended overcorrection.' And 'The Krackow Effect (The Biology of Compression): ...applying dynamic compression across an osteotomy site in soft, cancellous bone leads to the micro-crushing of the bony trabeculae. This physical impaction can slightly increase the final angular correction beyond what was geometrically resected with the saw.'Option A is incorrect:Insufficient preservation of the concave hinge would lead to instability and potentially hardware failure, not necessarily overcorrection of the angle.Option B is incorrect:Aggressive periosteal stripping on the convex side risks avascular necrosis, but not direct overcorrection of the angle.Option D is incorrect:Performing an osteotomy away from the CORA without translation (Rule Three violation) leads to a residual translation deformity and uncorrected MAD, not an angular overcorrection.Option E is incorrect:Non-parallel cuts lead to out-of-plane deformities, not necessarily an overcorrection in the intended plane.

Question 797

Topic: Total Hip Arthroplasty (THA)

A surgeon plans to correct a mid-diaphyseal tibial angular deformity. According to Paley's Rule 1 of osteotomy, if the osteotomy and the hinge axis are both placed exactly at the Center of Rotation of Angulation (CORA), what is the resulting geometric correction?

. Pure angular correction without any translation at the osteotomy site
. Angular correction with deliberate translation at the osteotomy site
. Pure translation of the distal segment without angular correction
. Angular correction with an unintended secondary translation deformity
. Correction of angulation but creation of a leg length discrepancy

Correct Answer & Explanation

. Pure angular correction without any translation at the osteotomy site

Explanation

According to Paley's Rule 1, placing both the osteotomy and the correction hinge at the CORA results in pure angular correction. The anatomic axes will become collinear without any translation at the osteotomy site.

Question 798

Topic: Total Hip Arthroplasty (THA)

According to Paley's Rule 2 of deformity correction, if the osteotomy is performed at a level different from the CORA, but the Angulation Correction Axis (ACA) remains at the CORA, what is the expected anatomical outcome?

. An uncompensated leg length discrepancy will invariably result.
. The proximal and distal axes will remain parallel but not collinear.
. Iatrogenic translation of the mechanical axis will occur.
. The mechanical axes will realign, but collinear translation will occur at the osteotomy site.
. The mechanical axes will realign perfectly without any local translation at the osteotomy site.

Correct Answer & Explanation

. The mechanical axes will realign, but collinear translation will occur at the osteotomy site.

Explanation

Paley's Rule 2 states that if the ACA is at the CORA but the osteotomy is not, the mechanical axes will fully realign. However, there will be an obligatory translation of the bone ends at the osteotomy site.

Question 799

Topic: Total Hip Arthroplasty (THA)

A 16-year-old patient with a severe varus deformity of the tibia is undergoing correction with an Ilizarov external fixator. According to Paley's Rule 1 of deformity correction, if the osteotomy and the hinge of the external fixator are both placed exactly at the Center of Rotation of Angulation (CORA), which of the following best describes the resulting alignment?

. The mechanical axes will realign with translation occurring at the osteotomy site.
. The mechanical axes will remain parallel but translated, creating a zig-zag deformity.
. The mechanical axes will realign completely without any translation at the osteotomy site.
. The deformity will be overcorrected into valgus due to the hinge placement.
. The osteotomy site will distract unequally, leading to a leg length discrepancy.

Correct Answer & Explanation

. The mechanical axes will realign completely without any translation at the osteotomy site.

Explanation

Paley's Rule 1 states that when the osteotomy and the hinge (axis of correction) are both located at the CORA, the mechanical axes will realign perfectly. This results in pure angulation without translation at the osteotomy site.

Question 800

Topic: Total Hip Arthroplasty (THA)

A 22-year-old patient is undergoing distraction osteogenesis for a post-traumatic tibial leg length discrepancy. After the corticotomy, the surgeon waits 7 days before initiating distraction. What is the primary biological rationale for this latency period?

. To prevent early pin tract infections.
. To allow the hematoma to organize and initial angiogenesis to occur.
. To permit complete endochondral ossification of the fracture gap.
. To decrease the risk of deep vein thrombosis.
. To allow the patient's pain to subside before applying mechanical stress.

Correct Answer & Explanation

. To allow the hematoma to organize and initial angiogenesis to occur.

Explanation

The latency period (typically 5-10 days) allows the fracture hematoma to organize and mesenchymal stem cells to begin the early phases of angiogenesis and soft callus formation. Premature distraction disrupts this delicate vascular network, leading to poor regenerate bone.

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