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Lower Extremity Trauma MCQs

Practice Set 34 of 34

This practice set contains high-yield board review questions covering key concepts in Lower Extremity Trauma. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 661

Topic: Lower Extremity Trauma

A 10-year-old girl with a predicted leg length discrepancy of 3 cm at skeletal maturity is scheduled for a distal femoral epiphysiodesis. According to the Menelaus method and Green-Anderson growth data, approximately how much lower extremity growth per year is expected specifically from the distal femur?

. 6 mm/year
. 10 mm/year
. 13 mm/year
. 16 mm/year
. 20 mm/year

Correct Answer & Explanation

. 10 mm/year

Explanation

The distal femur contributes approximately 10 mm (3/8 inch) of growth per year until skeletal maturity. In contrast, the proximal tibia contributes approximately 6 mm (1/4 inch) per year.

Question 662

Topic: Lower Extremity Trauma

The Menelaus method is a simplified arithmetic rule used to estimate remaining growth for timing epiphysiodesis in leg length discrepancies. This method assumes that lower extremity growth ceases at what ages for girls and boys, respectively?

. 12 and 14 years
. 13 and 15 years
. 14 and 16 years
. 16 and 18 years
. 18 and 21 years

Correct Answer & Explanation

. 14 and 16 years

Explanation

The Menelaus arithmetic method simplifies growth remaining calculations by assuming growth ceases at age 14 for girls and age 16 for boys. It applies standard growth rates of 10 mm/yr for the distal femur and 6 mm/yr for the proximal tibia during these remaining years.

Question 663

Topic: Lower Extremity Trauma

A patient with osteoarthritis presents with a varus knee deformity. Standing full-length radiographic analysis reveals a mechanical lateral distal femoral angle (mLDFA) of 88 degrees and a mechanical medial proximal tibial angle (mMPTA) of 78 degrees. What is the primary source of the mechanical axis deviation?

. Femoral shaft bowing
. Distal femur varus deformity
. Proximal tibia varus deformity
. Intra-articular knee joint wear
. Combined femoral and tibial deformity

Correct Answer & Explanation

. Proximal tibia varus deformity

Explanation

The normal mLDFA is 85-90 degrees (average 88) and normal mMPTA is 85-90 degrees (average 87). An mMPTA of 78 degrees is abnormally low, unequivocally indicating a proximal tibia varus deformity as the primary driver of the alignment anomaly.

Question 664

Topic: Lower Extremity Trauma

Evaluating a lower extremity deformity, the mechanical axis deviation (MAD) falls deep into the lateral compartment of the knee. The mechanical lateral distal femoral angle (mLDFA) is 75 degrees and the medial proximal tibial angle (MPTA) is 88 degrees. What is the primary source of the deformity?

. Femoral varus
. Femoral valgus
. Tibial varus
. Tibial valgus
. Combined femoral and tibial valgus

Correct Answer & Explanation

. Femoral valgus

Explanation

The normal mLDFA is approximately 88 degrees. An mLDFA of 75 degrees indicates a smaller than normal angle, meaning the distal femur is structurally in severe valgus. The normal MPTA confirms the tibia is not contributing to the primary angular deformity.

Question 665

Topic: Lower Extremity Trauma



When establishing reference lines for complex tibial deformity planning, the mechanical axis of the normal tibia is defined as a line connecting the center of the ankle plafond to which of the following proximal landmarks?

. The center of the tibial plateau
. The medial tibial spine
. The center of the intercondylar notch of the femur
. The lateral aspect of the medial tibial plateau
. The tip of the fibular head

Correct Answer & Explanation

. The center of the tibial plateau

Explanation

The mechanical axis of the tibia is defined by a straight line connecting the center of the proximal tibial plateau (often just medial to the lateral tibial spine) to the center of the distal tibial plafond.

Question 666

Topic: Lower Extremity Trauma

When performing a medial opening wedge high tibial osteotomy (HTO) for isolated medial compartment osteoarthritis, restoring the mechanical axis to intersect the tibial plateau at what percentage of its width (from medial to lateral) is recommended for optimal load redistribution?

. 30-35%
. 50%
. 62-66%
. 75-80%
. 85-90%

Correct Answer & Explanation

. 62-66%

Explanation

For medial compartment osteoarthritis, an HTO aims to shift the weight-bearing axis laterally to offload the diseased medial compartment. The target correction is a slight valgus overcorrection, intersecting the 62% to 66% coordinate of the tibial plateau width.

Question 667

Topic: Lower Extremity Trauma

A patient is planned for a medial opening wedge high tibial osteotomy (HTO) for medial compartment osteoarthritis with a varus deformity. To achieve optimal longevity of the joint, where should the postoperative mechanical axis line ideally pass through the knee?

. Through the center of the tibial spines.
. Through the center of the medial compartment.
. At the 62.5% coordinate of the tibial plateau from medial to lateral (Fujisawa point).
. At the 80% coordinate of the tibial plateau from medial to lateral.
. Slightly medial to the lateral tibial spine (40% coordinate).

Correct Answer & Explanation

. At the 62.5% coordinate of the tibial plateau from medial to lateral (Fujisawa point).

Explanation

The Fujisawa point corresponds to roughly 62-62.5% across the tibial plateau (from medial to lateral). Targeting the mechanical axis through this slightly lateral point reliably offloads the medial compartment and improves HTO survivorship.

Question 668

Topic: Lower Extremity Trauma

When evaluating coronal plane lower extremity deformity, which of the following values indicates a pathologic varus deformity originating from the distal femur?

. mLDFA of 87 degrees
. mLDFA of 96 degrees
. mLDFA of 80 degrees
. MPTA of 87 degrees
. MPTA of 95 degrees

Correct Answer & Explanation

. mLDFA of 87 degrees

Explanation

The normal mechanical lateral distal femoral angle (mLDFA) is approximately 87 degrees. An mLDFA greater than 90 degrees indicates that the distal femur is in varus, while an mLDFA less than 85 degrees indicates valgus.

Question 669

Topic: Lower Extremity Trauma



A high tibial osteotomy (HTO) is planned for a patient with medial compartment osteoarthritis and varus alignment. To reliably unload the medial compartment and halt disease progression, the mechanical axis should be corrected to pass through which specific coordinate of the tibial plateau (measured from medial to lateral)?

. 30-40%
. 50% (neutral)
. 62-65% (Fujisawa point)
. 80-90%
. 100%

Correct Answer & Explanation

. 62-65% (Fujisawa point)

Explanation

To predictably relieve symptoms in a medial compartment HTO, the mechanical axis is intentionally shifted laterally to the Fujisawa point. This point is located at 62.5% of the tibial plateau width (measured from medial to lateral).

Question 670

Topic: Lower Extremity Trauma

Which of the following radiographic findings is most characteristic of "dysostosis multiplex," the constellation of skeletal abnormalities seen in patients with Mucopolysaccharidoses?

. Erlenmeyer flask deformity of the distal femur
. Oar-shaped ribs, thickened clavicles, and bullet-shaped vertebrae
. Pencil-in-cup deformities of the phalanges
. Profound diaphyseal endosteal thickening with marrow obliteration
. Diffuse osteosclerosis creating a "bone-within-bone" appearance

Correct Answer & Explanation

. Oar-shaped ribs, thickened clavicles, and bullet-shaped vertebrae

Explanation

Dysostosis multiplex encompasses the skeletal manifestations of MPS, classically presenting with bullet-shaped hypoplastic vertebrae (leading to gibbus), oar-shaped (spatulate) ribs, J-shaped sella turcica, and thickened clavicles.

Question 671

Topic: Lower Extremity Trauma

In evaluating a patient for lower extremity deformity, a standing full-length anteroposterior radiograph is obtained. The mechanical axis line passes medial to the center of the knee joint. The mechanical lateral distal femoral angle (mLDFA) is 95 degrees, and the medial proximal tibial angle (MPTA) is 87 degrees. What is the primary source of the varus deformity?

. Tibial deformity
. Femoral deformity
. Joint laxity
. Patellofemoral dysplasia
. Both femoral and tibial deformity

Correct Answer & Explanation

. Femoral deformity

Explanation

A normal mLDFA is 85-90 degrees (average 88) and a normal MPTA is 85-90 degrees (average 87). An mLDFA of 95 degrees indicates excessive varus alignment originating in the distal femur, whereas the tibial MPTA is within normal limits.

Question 672

Topic: Lower Extremity Trauma

A patient presents with knee pain and a suspected lower extremity malalignment. Full-length standing radiographs are obtained. Which of the following best defines the mechanical axis deviation (MAD)?

. The angle between the mechanical axis of the femur and the tibia
. The perpendicular distance from the center of the knee joint to the mechanical axis line
. The angle between the anatomic and mechanical axes of the femur
. The distance between the anatomic and mechanical axes at the distal femur
. The sum of the medial proximal tibial angle and the lateral distal femoral angle

Correct Answer & Explanation

. The perpendicular distance from the center of the knee joint to the mechanical axis line

Explanation

Mechanical axis deviation (MAD) is mathematically defined as the perpendicular distance (in millimeters) from the center of the knee joint to the mechanical axis line extending from the center of the femoral head to the center of the ankle mortise.

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