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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 41 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 801

Topic: Total Hip Arthroplasty (THA)

The Paley multiplier method is frequently used to predict leg length discrepancy (LLD) at skeletal maturity. Which of the following data points is the most critical to accurately calculate the predicted LLD at skeletal maturity using this method?

. The patient's current LLD and skeletal age
. The patient's chronological age and current LLD only
. The patient's current LLD and parental heights
. The patient's bone age and exact femoral length only
. The patient's chronological age and body weight

Correct Answer & Explanation

. The patient's current LLD and skeletal age

Explanation

The Paley multiplier method predicts discrepancy at skeletal maturity by multiplying the current LLD by an age- and gender-specific multiplier. It is most accurate when the patient's current LLD and true skeletal age (rather than chronological age) are used.

Question 802

Topic: Total Hip Arthroplasty (THA)

A 12-year-old boy presents with a leg length discrepancy (LLD) secondary to prior physeal arrest. The surgeon decides to use the Paley Multiplier Method for preoperative planning. What is the primary purpose of this method?

. To calculate the safe daily rate of distraction osteogenesis
. To predict the final lower limb length discrepancy at skeletal maturity
. To determine the precise location of the anatomical CORA
. To select the correct ring size for a circular external fixator
. To estimate the duration of the consolidation phase

Correct Answer & Explanation

. To predict the final lower limb length discrepancy at skeletal maturity

Explanation

The Paley Multiplier Method utilizes age- and gender-specific coefficients to predict the limb length at skeletal maturity. It is highly accurate for calculating final leg length discrepancy and timing epiphysiodesis or lengthening procedures.

Question 803

Topic: 3. Adult Reconstruction (Hip & Knee)

In the preoperative radiographic assessment of the lower extremity, differentiating between the mechanical and anatomic axes of the femur is critical. What is the normal relationship between the femoral anatomic axis and the femoral mechanical axis?

. They are perfectly collinear
. The anatomic axis is 3 degrees varus to the mechanical axis
. The anatomic axis is approximately 7 degrees valgus to the mechanical axis
. The mechanical axis is 7 degrees valgus to the anatomic axis
. The anatomic axis is 15 degrees valgus to the mechanical axis

Correct Answer & Explanation

. The anatomic axis is 3 degrees varus to the mechanical axis

Explanation

The normal anatomic axis of the femur is typically oriented in 7 degrees of valgus (range 5-9 degrees) relative to the mechanical axis of the femur. This relationship dictates how intra-operative intramedullary alignment guides are set during knee arthroplasty and deformity correction.

Question 804

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with an Ilizarov circular frame applied for a tibial malunion complains of erythema, mild swelling, and serous drainage around a single tensioned wire. There is no systemic fever, and radiographs show no wire loosening or osteolysis. What is the most appropriate initial management?

. Immediate surgical removal of the wire and frame adjustment
. Admission for intravenous vancomycin and operative debridement
. Initiation of oral antibiotics and enhanced local pin site care
. Slacking the tension on the wire to reduce soft tissue pressure
. Exchange of the fine wire for a 5.0 mm half-pin

Correct Answer & Explanation

. Initiation of oral antibiotics and enhanced local pin site care

Explanation

Superficial pin tract infections (Checketts-Otterburn Grade 1 or 2) present with local erythema and drainage without deep loosening. They are best managed initially with enhanced local pin care and a short course of oral antibiotics covering skin flora.

Question 805

Topic: Total Knee Arthroplasty (TKA)

According to Paley's Rule 1 of deformity correction, if the osteotomy and the hinge (axis of rotation) are both placed exactly at the Center of Rotation of Angulation (CORA), what is the resultant anatomic and mechanical alignment?

. The mechanical axis is restored, but the anatomic axis remains translated.
. Both the mechanical and anatomic axes are restored without any translation.
. The anatomic axis is corrected, but the mechanical axis shifts laterally.
. A secondary translation deformity is created requiring a second osteotomy.
. The mechanical axis becomes parallel but not collinear to the normal axis.

Correct Answer & Explanation

. Both the mechanical and anatomic axes are restored without any translation.

Explanation

Paley's Rule 1 states that when the osteotomy and the hinge are both placed at the CORA, the bone undergoes pure angulation. This fully restores both the anatomic and mechanical axes without introducing any translation.

Question 806

Topic: Total Hip Arthroplasty (THA)

You are reviewing the alignment parameters of a 50-year-old patient.

The patient's mechanical axis deviation (MAD) is perfectly normal (0 mm). However, the knee joint line obliquity is significantly altered relative to the floor. Which of the following best explains this phenomenon?

. A pure intra-articular cartilage defect of the medial compartment
. A compensatory deformity with equal and opposite deformities in the femur and tibia
. A solitary diaphyseal deformity of the tibia
. A leg length discrepancy exceeding 2 cm
. Isolated lateral collateral ligament insufficiency

Correct Answer & Explanation

. A compensatory deformity with equal and opposite deformities in the femur and tibia

Explanation

Compensatory deformities (e.g., a valgus distal femur paired with a varus proximal tibia of equal magnitude) keep the mechanical axis passing through the center of the knee, resulting in a normal MAD, but cause the joint line to be oblique to the ground.

Question 807

Topic: Total Hip Arthroplasty (THA)

During the evaluation of a patient with a post-traumatic knee deformity, a weight-bearing radiograph reveals an abnormal Joint Line Convergence Angle (JLCA) of 6 degrees, opening laterally. What does an abnormal JLCA primarily indicate in the context of deformity planning?

. Intra-articular fracture step-off.
. A primary diaphyseal bowing deformity.
. Ligamentous laxity or unilateral cartilage loss.
. A pure translational deformity of the metaphysis.
. An underlying leg length discrepancy.

Correct Answer & Explanation

. Ligamentous laxity or unilateral cartilage loss.

Explanation

The JLCA measures the parallelism of the distal femoral and proximal tibial articular surfaces (normally 0-2 degrees). An increased JLCA typically indicates asymmetric cartilage loss or collateral ligament laxity, which must be accounted for to prevent undercorrection or overcorrection.

Question 808

Topic: 3. Adult Reconstruction (Hip & Knee)

A surgeon uses a Taylor Spatial Frame (TSF) to correct a complex multi-planar deformity of the femur. The mathematical software requires specific parameters to generate a correction schedule. Which of the following best describes the fundamental kinematic mechanism of the TSF?

. Ilizarov tension-stress principle based on single-axis hinges.
. Stewart-Gough platform concept providing 6 degrees of freedom.
. Charnley's principle of low-friction arthroplasty.
. The tension band principle using eccentric loading.
. The Hueter-Volkmann principle of physeal growth modulation.

Correct Answer & Explanation

. Stewart-Gough platform concept providing 6 degrees of freedom.

Explanation

The Taylor Spatial Frame is a hexapod external fixator that utilizes the Stewart-Gough platform concept. It consists of two rings connected by six struts, allowing simultaneous correction in all 6 degrees of freedom (angulation and translation in three planes).

Question 809

Topic: Total Hip Arthroplasty (THA)

During the all-arthroscopic extensive anterior and posterior synovectomy for this patient's diffuse TGCT of the knee, a critical technical challenge is ensuring thorough clearance of the posterior compartments. Which of the following best describes the arthroscopic approach to address the posterior compartments while minimizing neurovascular risk?

. Rely solely on trans-notch visualization from anterior portals for posterior clearance.
. Perform an open posterior approach as the primary method for all posterior disease.
. Establish posteromedial and posterolateral portals under direct intra-articular visualization, carefully avoiding neurovascular structures.
. Utilize a posterior midline portal to access both posteromedial and posterolateral compartments simultaneously.
. Perform a complete posterior capsulectomy through a single large posterior incision.

Correct Answer & Explanation

. Establish posteromedial and posterolateral portals under direct intra-articular visualization, carefully avoiding neurovascular structures.

Explanation

Correct Answer: C - Establish posteromedial and posterolateral portals under direct intra-articular visualization, carefully avoiding neurovascular structures.The case emphasizes: "Thorough clearance of the posterior compartments is the most critical step in preventing recurrence in diffuse TGCT. Trans-notch visualization is insufficient for a complete posterior synovectomy." It then describes the technique: "An 18-gauge spinal needle was used to localize a posteromedial portal under direct intra-articular visualization, ensuring it was superior to the joint line and posterior to the medial collateral ligament to avoid the saphenous nerve and vein. ... Similarly, a posterolateral portal was established under direct visualization, taking extreme care to stay anterior to the biceps femoris tendon and fibular head to protect the common peroneal nerve." This highlights the importance of direct visualization and careful portal placement.A. Rely solely on trans-notch visualization from anterior portals for posterior clearance:The case explicitly states this is "insufficient for a complete posterior synovectomy," leading to higher recurrence rates.B. Perform an open posterior approach as the primary method for all posterior disease:While an open posterior approach is an option, the case states that an all-arthroscopic approach was chosen because "there was no extra-articular extension... that would mandate an open posterior approach." Modern arthroscopic techniques allow for thorough posterior clearance without the morbidity of an open approach in many cases.D. Utilize a posterior midline portal to access both posteromedial and posterolateral compartments simultaneously:A posterior midline portal is not a standard or safe approach for comprehensive posterior knee arthroscopy due to the risk to the popliteal neurovascular bundle. Separate posteromedial and posterolateral portals are used.E. Perform a complete posterior capsulectomy through a single large posterior incision:This describes an open posterior approach, which was not the chosen method for this patient and is associated with higher morbidity and arthrofibrosis compared to arthroscopy.

Question 810

Topic: 3. Adult Reconstruction (Hip & Knee)

While Pigmented Villonodular Synovitis (PVNS) most commonly affects the knee, when it presents in the shoulder, it can often be mistaken for which of the following conditions due to its characteristic erosive nature on radiographs?

. Osteoarthritis
. Rheumatoid arthritis
. Synovial chondromatosis
. Amyloid arthropathy
. Avascular necrosis

Correct Answer & Explanation

. Rheumatoid arthritis

Explanation

In joints with tight capsules like the shoulder and hip, the proliferative synovium of PVNS causes increased intra-articular pressure, leading to extrinsic bone erosions on both sides of the joint. This radiographic appearance can mimic erosive inflammatory arthropathies like Rheumatoid arthritis.

Question 811

Topic: Total Hip Arthroplasty (THA)

When evaluating a patient for lower extremity deformity, the mechanical axis deviation (MAD) is measured.

If the MAD falls medial to the center of the knee joint, what is the next step in the standard Malalignment Test to accurately identify the source of the deformity?

. Measure the joint line convergence angle (JLCA)
. Measure the mechanical lateral distal femoral angle (mLDFA)
. Measure the mechanical medial proximal tibial angle (mMPTA)
. Measure the anatomic axis of the femur
. Compare the leg length discrepancy using scanograms

Correct Answer & Explanation

. Measure the mechanical lateral distal femoral angle (mLDFA)

Explanation

Once a medial MAD (varus) is identified, the standard Malalignment Test dictates evaluating the joint orientation angles starting proximally. The mechanical lateral distal femoral angle (mLDFA) is measured first to determine if the femur is the source of the deformity.

Question 812

Topic: Total Knee Arthroplasty (TKA)

A 60-year-old patient presents with severe knee osteoarthritis and a significant varus deformity. Preoperative planning for a corrective osteotomy involves assessing the overall global limb alignment. According to the text, which specific line is considered the most important for this assessment?

. A. The anatomic axis of the femur.
. B. The anatomic axis of the tibia.
. C. The mechanical axis of the entire limb (Mikulicz Line).
. D. The line connecting the center of the femoral head to the greater trochanter.
. E. The line connecting the midpoint of the tibial spines to the center of the ankle plafond.

Correct Answer & Explanation

. C. The mechanical axis of the entire limb (Mikulicz Line).

Explanation

Correct Answer: CThe text defines the 'Entire Limb (Mikulicz Line)' as 'A single line from the center of the femoral head to the center of the ankle. This is the most important line for assessing overall global limb alignment.' Restoring this line to pass through the center of the knee is the biomechanical imperative of deformity correction.Incorrect Options:A. The anatomic axis of the femur:While important for intramedullary nailing, the femoral anatomic axis does not represent the global mechanical alignment of the entire limb due to its divergence from the mechanical axis.B. The anatomic axis of the tibia:Similar to the femoral anatomic axis, the tibial anatomic axis represents the mid-diaphyseal line of the tibia, not the global mechanical alignment of the entire limb.D. The line connecting the center of the femoral head to the greater trochanter:This line is not a standard axis for assessing lower extremity alignment in the frontal plane.E. The line connecting the midpoint of the tibial spines to the center of the ankle plafond:This describes the mechanical axis of thetibiaonly, not the overall global limb alignment from hip to ankle.

Question 813

Topic: Total Hip Arthroplasty (THA)

A 16-year-old male presents with a leg length discrepancy (LLD) and requires lengthening of the right tibia using an Ilizarov frame. During the distraction phase, the patient develops a rigid plantarflexion deformity. Which of the following is the primary pathoanatomical cause of this specific complication?

. Overactivity of the tibialis anterior muscle.
. Relative shortening and contracture of the gastrosoleus complex.
. Premature consolidation of the fibular osteotomy.
. Inadvertent tethering of the deep peroneal nerve.
. Subluxation of the distal tibiofibular joint.

Correct Answer & Explanation

. Relative shortening and contracture of the gastrosoleus complex.

Explanation

Equinus contracture is the most common complication during tibial lengthening. It occurs because the gastrosoleus complex spans two joints and becomes relatively shorter and tighter as the tibia is distracted.

Question 814

Topic: Total Hip Arthroplasty (THA)

A 30-year-old patient has a complex tibial deformity characterized by varus, procurvatum, and internal rotation. The surgeon elects to use a Taylor Spatial Frame (TSF). What engineering concept allows the TSF to correct all six degrees of freedom simultaneously?

. The Ilizarov rigid ring principle.
. The Charnley low-friction principle.
. The Stewart-Gough platform concept.
. The tension-band wiring mechanism.
. The Hooke's law of elasticity mechanism.

Correct Answer & Explanation

. The Stewart-Gough platform concept.

Explanation

The TSF is based on the Stewart-Gough platform, a hexapod mechanism that allows movement in all six degrees of freedom. A computer program calculates a "virtual hinge" to correct multi-planar deformities simultaneously.

Question 815

Topic: Total Hip Arthroplasty (THA)

During a multi-apical tibial deformity correction, a surgeon identifies two separate CORAs. If the surgeon decides to perform only a single osteotomy located exactly halfway between the two CORAs and corrects the angulation perfectly, what unintended deformity will inevitably result?

. Leg length discrepancy
. Rotational malalignment
. A translation deformity of the mechanical axis
. A reversed joint line convergence angle
. Intra-articular valgus

Correct Answer & Explanation

. A translation deformity of the mechanical axis

Explanation

Correcting a multi-apical deformity with a single osteotomy between the CORAs effectively follows Rule 3. While angulation can be corrected, the mechanical axes will remain parallel but offset, creating a translation deformity.

Question 816

Topic: Total Hip Arthroplasty (THA)

A 32-year-old female presents with a diaphyseal femoral deformity. The surgeon places the hinge at the CORA but performs the osteotomy at a different level due to poor soft tissue quality. According to Paley's principles, what is the expected outcome upon correction?

. Pure angulation at the osteotomy site with restoration of the mechanical axis.
. Angulation and translation at the osteotomy site with restoration of the mechanical axis.
. Angulation and translation at the osteotomy site without restoration of the mechanical axis.
. Pure translation at the osteotomy site without restoration of the mechanical axis.
. Translation that corrects the axis but introduces a leg length discrepancy.

Correct Answer & Explanation

. Angulation and translation at the osteotomy site with restoration of the mechanical axis.

Explanation

Paley's Osteotomy Rule 2 states that if the hinge is at the CORA and the osteotomy is at a different level, the correction will result in both angulation and translation at the osteotomy site, but the mechanical axis will be restored.

Question 817

Topic: Total Hip Arthroplasty (THA)

A patient has a congenital distal femoral valgus deformity (mLDFA = 75°). Over time, the proximal tibia develops a varus deformity (MPTA = 75°). The overall mechanical axis deviation (MAD) is currently 0 mm. What radiographic finding is most likely to be significantly abnormal in this patient?

. Mechanical Axis Deviation
. Joint Line Obliquity
. Leg Length Discrepancy
. Neck-Shaft Angle
. Lateral Distal Tibial Angle (LDTA)

Correct Answer & Explanation

. Joint Line Obliquity

Explanation

When adjacent bones have opposing deformities (femoral valgus and tibial varus) that cancel each other out, the overall MAD may be zero. However, this compensatory mechanism leads to an abnormal, non-horizontal knee joint line (joint line obliquity).

Question 818

Topic: Total Hip Arthroplasty (THA)

A 24-year-old male with a symptomatic tibial varus deformity is planned for correction using Paley's principles. Preoperative planning identifies a single Center of Rotation of Angulation (CORA) in the mid-diaphysis. If the surgeon decides to perform the osteotomy exactly at the CORA and places the axis of correction (hinge) exactly at the CORA, what is the anticipated radiographic and mechanical outcome based on Paley's Rule 1?

. The deformity corrects with an expected secondary translation of the bone ends.
. The angular deformity corrects purely without translation, resulting in collinear mechanical axes.
. The mechanical axes remain parallel but laterally translated.
. A significant leg length discrepancy will inevitably result.
. The mechanical axes will deviate by the exact angle of the original deformity.

Correct Answer & Explanation

. The angular deformity corrects purely without translation, resulting in collinear mechanical axes.

Explanation

According to Paley's Osteotomy Rule 1, placing both the osteotomy and the axis of correction (hinge) at the CORA results in pure angulation correction. This optimally realigns the proximal and distal mechanical axes without inducing unwanted translation.

Question 819

Topic: Total Knee Arthroplasty (TKA)

When planning a deformity correction, multiple CORAs may be identified in a single bone segment. Which of the following best describes the primary biomechanical indication for utilizing a double-level osteotomy rather than a single-level correction?

. When a single CORA is located in the narrowest part of the diaphysis.
. When the mechanical axis line deviates more than 1 cm from the anatomical axis.
. When a single osteotomy would result in unacceptable translation of the anatomical axis to restore mechanical alignment.
. Whenever there is a combined angular and torsional deformity.
. When the deformity is strictly within the metaphysis.

Correct Answer & Explanation

. When a single osteotomy would result in unacceptable translation of the anatomical axis to restore mechanical alignment.

Explanation

Multiple CORAs or a large diaphyseal bow corrected with a single osteotomy near the joint may result in significant, unacceptable bone translation. A double-level osteotomy restores the mechanical axis while maintaining the anatomical axis within the soft tissue envelope.

Question 820

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old patient with a long-standing varus deformity of the knee is being planned for a high tibial osteotomy. Preoperative radiographs show a Mechanical Axis Deviation (MAD) of 12 mm medial to the knee center. The Medial Proximal Tibial Angle (MPTA) is 80° (normal 85°-90°), indicating a proximal tibial varus. However, the Joint Line Convergence Angle (JLCA) is measured at 4° (normal 0°-2°). How should the surgeon account for the elevated JLCA in the surgical plan?

. The JLCA is irrelevant for bony correction and can be ignored.
. The bony correction should be reduced to avoid overcorrection, as the joint itself contributes to valgus.
. The bony correction should be increased (over-corrected) to compensate for the intra-articular laxity/bone loss.
. The osteotomy should be performed at the CORA to minimize translation.
. The patient requires a total knee arthroplasty instead of an osteotomy.

Correct Answer & Explanation

. The bony correction should be increased (over-corrected) to compensate for the intra-articular laxity/bone loss.

Explanation

Correct Answer: CThe Joint Line Convergence Angle (JLCA) measures the angle between the distal femoral and proximal tibial joint lines. A value greater than 2° suggests intra-articular pathology, such as asymmetric cartilage loss or ligamentous laxity. This 'intra-articular' component contributes to the overall limb deformity. If a patient has a varus deformity but a JLCA of 4° (indicating lateral compartment laxity or medial compartment cartilage loss contributing to the varus), correcting only the bony MPTA to a normal angle will result in a limb that is still in varus when weight-bearing. Therefore, the surgeon mustover-correct the boneto account for the soft tissue joint line opening or closing. Ignoring the JLCA (Option A) or reducing the correction (Option B) would lead to under-correction of the overall limb alignment. Option D is about osteotomy placement, not the magnitude of correction. Option E is a treatment decision not directly related to how to account for JLCA in an osteotomy plan.

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