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Lower Extremity Trauma MCQs

Practice Set 8 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 141

Topic: Lower Extremity Trauma

The 'lengthening over a nail' (LON) technique combines an external fixator with an intramedullary nail. What is the primary clinical advantage of this technique compared to classic Ilizarov lengthening?

. It allows for a significantly faster daily distraction rate.
. It minimizes the time the patient must wear the external fixator.
. It completely eliminates the risk of deep infection.
. It relies solely on endosteal bone formation without periosteal contribution.
. It automatically prevents any translation during the distraction phase.

Correct Answer & Explanation

. It minimizes the time the patient must wear the external fixator.

Explanation

Lengthening over a nail allows the external fixator to be removed immediately after the distraction phase is complete, as the nail is locked to maintain length. This dramatically reduces the time the patient is burdened by the external frame.

Question 142

Topic: Lower Extremity Trauma

When planning a sagittal plane correction of a proximal tibial recurvatum deformity, the normal posterior proximal tibial angle (PPTA) must be considered. What is the normal anatomic range for the PPTA?

. 70°-75°
. 77°-84°
. 85°-90°
. 91°-95°
. 96°-100°

Correct Answer & Explanation

. 77°-84°

Explanation

The normal PPTA is approximately 81°, with a normal range of 77°-84°. This represents the normal posterior slope of the tibial plateau in the sagittal plane.

Question 143

Topic: Lower Extremity Trauma

A 45-year-old female presents with a mechanical axis deviation (MAD) of 20 mm medial to the knee center. The mechanical lateral distal femoral angle (mLDFA) is 95 degrees, and the medial proximal tibial angle (MPTA) is 87 degrees. Which of the following is the primary source of the deformity?

. Femoral varus
. Femoral valgus
. Tibial varus
. Tibial valgus
. Intra-articular knee deformity

Correct Answer & Explanation

. Femoral varus

Explanation

Normal mLDFA is approximately 88 degrees (range 85-90). An mLDFA of 95 degrees indicates a varus deformity of the distal femur, which correlates with the overall medial mechanical axis deviation.

Question 144

Topic: Lower Extremity Trauma

A 30-year-old patient presents with a post-traumatic femoral valgus deformity requiring corrective osteotomy. Preoperative planning identifies a single Center of Rotation of Angulation (CORA) in the distal femur. The surgeon plans to use a monolateral external fixator for gradual correction. According to Paley's Osteotomy Rule One, which of the following statements accurately describes the geometric outcome if both the osteotomy and the hardware hinge are placed precisely at the CORA?

. A. The correction will result in angulation combined with a planned, collinear translation of the bone ends.
. B. The correction will result in pure angulation without any secondary translation.
. C. The correction will result in angulation and a non-collinear, unplanned translation (a zigzag deformity).
. D. The correction will primarily achieve limb lengthening with minimal angular change.
. E. The correction will require simultaneous compression to prevent secondary lengthening.

Correct Answer & Explanation

. B. The correction will result in pure angulation without any secondary translation.

Explanation

Correct Answer: BPaley's Osteotomy Rule One states that when the osteotomy and the hardware hinge are both placed exactly at the CORA, the correction results in pure angulation without any secondary translation. This is the geometrically ideal scenario where the bone segments pivot perfectly around the apex of the deformity, and the proximal and distal axes become completely collinear without any offset. Option A describes Rule Two, where the osteotomy is away from the CORA but the hinge is at the CORA. Option C describes Rule Three, where both the osteotomy and hinge are away from the CORA, leading to an unplanned zigzag deformity. Options D and E describe secondary effects or primary goals not directly related to the fundamental geometric outcome of Rule One.

Question 145

Topic: Lower Extremity Trauma

A 62-year-old male presents with progressive knee pain. A full-length, weight-bearing radiograph is obtained, as shown in the image below. Which of the following lines on the provided radiograph accurately represents the Mechanical Axis of the lower limb?

. A. A line from the anterior superior iliac spine to the medial malleolus.
. B. A line from the greater trochanter to the lateral malleolus.
. C. A line from the exact center of the femoral head to the center of the ankle mortise.
. D. A line from the center of the knee joint to the center of the hip joint.
. E. A line connecting the midpoints of the femoral and tibial shafts.

Correct Answer & Explanation

. C. A line from the exact center of the femoral head to the center of the ankle mortise.

Explanation

Correct Answer: CThe mechanical axis is defined as a straight line drawn from the exact center of the femoral head to the center of the ankle mortise on a full-length, weight-bearing, standing radiograph (teleoroentgenogram). This definition is a cornerstone of lower extremity alignment analysis in deformity correction.Option Ais incorrect because the anterior superior iliac spine and medial malleolus are not the defined landmarks for the mechanical axis.Option Bis incorrect as the greater trochanter and lateral malleolus are not the correct anatomical points for defining the mechanical axis.Option Dis incorrect; while these are relevant joints, the mechanical axis connects the hip and ankle centers, not just the knee and hip.Option Eis incorrect; connecting the midpoints of the femoral and tibial shafts would represent an anatomical axis, not the mechanical axis, which is crucial for load bearing.

Question 146

Topic: Lower Extremity Trauma

A 60-year-old patient presents with severe knee pain and a "bow-legged" appearance. A full-length radiograph, as seen in , shows a Mechanical Axis Deviation passing 22mm medial to the knee center. Further analysis reveals an mLDFA of 80 degrees. Based on these findings, what is the most accurate interpretation of the patient's deformity?

. A. Overall valgus deformity with a normal distal femur.
. B. Overall varus deformity with a valgus deformity of the distal femur.
. C. Overall varus deformity with a varus deformity of the distal femur.
. D. Overall neutral alignment with a varus deformity of the distal femur.
. E. Overall valgus deformity with a varus deformity of the distal femur.

Correct Answer & Explanation

. C. Overall varus deformity with a varus deformity of the distal femur.

Explanation

Correct Answer: CLet's break down the findings:Mechanical Axis Deviation (MAD):The MAD passes 22mm medial to the knee center. According to the text, a medial deviation indicates a varus deformity. This aligns with the patient's "bow-legged" appearance. So, the patient has an overall varus deformity.Mechanical Lateral Distal Femoral Angle (mLDFA):The mLDFA is 80 degrees. The normal physiologic range for mLDFA is 85° to 90°. An angle of 80 degrees is less than the normal range, indicating that the distal femur is angled more acutely (medially) than normal, which signifies a varus deformity of the distal femur.Combining these, the patient has an overall varus deformity, and a significant contributing factor is a varus deformity originating in the distal femur.Option Ais incorrect because the MAD indicates varus, not valgus, and the mLDFA is abnormal.Option Bis incorrect because while the overall deformity is varus, the mLDFA of 80 degrees indicates a varus deformity of the distal femur, not a valgus deformity.Option Dis incorrect because a MAD of 22mm medial is not neutral alignment.Option Eis incorrect because the MAD indicates varus, not valgus, for the overall limb.

Question 147

Topic: Lower Extremity Trauma

A patient undergoing distal femoral lengthening over a motorized intramedullary nail is found to have rapid, dense regenerate bone formation on the two-week postoperative radiograph, raising concerns for premature consolidation. What is the most appropriate initial management step?

. Decrease the distraction rate to 0.5 mm per day
. Maintain the current distraction rate but prescribe NSAIDs
. Increase the distraction rate temporarily to 1.5 to 2.0 mm per day
. Return to the operating room for immediate re-osteotomy
. Stop distraction entirely and allow the bone to heal

Correct Answer & Explanation

. Increase the distraction rate temporarily to 1.5 to 2.0 mm per day

Explanation

If regenerate bone forms too rapidly and threatens premature consolidation, the appropriate management is to temporarily increase the distraction rate (e.g., to 1.5-2.0 mm/day) to keep the osteotomy gap open. Once the regenerate radiolucency widens appropriately, the standard 1 mm/day rate can be resumed.

Question 148

Topic: Lower Extremity Trauma

A patient with severe genu varum is evaluated with preoperative standing radiographs. The Mechanical Lateral Distal Femoral Angle (mLDFA) is 88 degrees, the Mechanical Medial Proximal Tibial Angle (MPTA) is 87 degrees, and the Joint Line Convergence Angle (JLCA) is 6 degrees with medial widening. Which of the following best describes the primary source of the varus deformity?

. Distal femoral osseous deformity.
. Proximal tibial osseous deformity.
. Diaphyseal tibial bowing.
. Intra-articular deformity due to collateral ligament laxity or asymmetric cartilage loss.
. Combined femoral and tibial osseous deformity.

Correct Answer & Explanation

. Intra-articular deformity due to collateral ligament laxity or asymmetric cartilage loss.

Explanation

Normal values for mLDFA (85-90 degrees) and MPTA (85-90 degrees) rule out significant osseous deformities in the distal femur or proximal tibia. A JLCA greater than 2 degrees indicates that the mechanical axis deviation is being driven by intra-articular factors, such as lateral collateral ligament laxity or medial compartment cartilage loss.

Question 149

Topic: Lower Extremity Trauma

A 35-year-old male is evaluated for a severe lower extremity deformity. Radiographic measurements reveal a mechanical axis deviation (MAD) of 25 mm lateral to the knee center. The mechanical Lateral Distal Femoral Angle (mLDFA) is 87 degrees, and the Mechanical Medial Proximal Tibial Angle (MPTA) is 98 degrees. The Joint Line Convergence Angle (JLCA) is 1 degree. Where is the primary source of the deformity?

. Distal femur.
. Proximal tibia.
. Intra-articular knee ligaments.
. Both distal femur and proximal tibia.
. Ankle joint.

Correct Answer & Explanation

. Proximal tibia.

Explanation

The normal mLDFA is 85-90 degrees, and the normal MPTA is 85-90 degrees. An MPTA of 98 indicates a significant valgus deformity originating in the proximal tibia, corresponding to the lateral MAD.

Question 150

Topic: Lower Extremity Trauma

Half-pins are inserted directly laterally into the distal third of the femur for a monolateral fixator construct. Which muscle is directly penetrated by these pins, frequently leading to postoperative knee stiffness?

. Rectus femoris.
. Vastus lateralis.
. Biceps femoris.
. Sartorius.
. Gracilis.

Correct Answer & Explanation

. Vastus lateralis.

Explanation

Pins placed in the true lateral position of the distal femur penetrate the vastus lateralis and the iliotibial band. Tethering of this extensor mechanism is a primary cause of significant knee stiffness during femoral lengthening.

Question 151

Topic: Lower Extremity Trauma

A 55-year-old female undergoes a full-length standing AP radiograph of her lower extremities as part of a workup for knee osteoarthritis. The radiograph reveals a Mechanical Axis Deviation (MAD) of 12mm lateral to the center of the knee joint. The surgeon suspects a distal femoral valgus deformity. Which of the following angles, if found to be outside its normal range, would most accurately pinpoint the distal femur as the source of this valgus deformity?

. A. Medial Proximal Tibial Angle (MPTA)
. B. Lateral Distal Tibial Angle (LDTA)
. C. Mechanical Lateral Distal Femoral Angle (mLDFA)
. D. Posterior Distal Femoral Angle (PDFA)
. E. Neck-Shaft Angle (NSA)

Correct Answer & Explanation

. C. Mechanical Lateral Distal Femoral Angle (mLDFA)

Explanation

Correct Answer: CThe correct answer is C, the mechanical Lateral Distal Femoral Angle (mLDFA). The case describes a patient with lateral MAD, indicating a valgus deformity, and the suspicion is that it originates from the distal femur. The mLDFA is defined as the angle between the mechanical axis of the femur and a line tangential to the most distal points on the convexity of the two femoral condyles. A normal mLDFA ranges from 85° to 90° (average ~88°). An abnormally low mLDFA (less than 85°) indicates distal femoral valgus (knock-knees), which would cause a lateral shift of the mechanical axis. Distal femoral osteotomies (DFOs) are specifically designed to correct the mLDFA.Option A (MPTA)assesses proximal tibial alignment (normal 85-90°). An abnormality here would indicate tibia vara or valga, not a distal femoral deformity.Option B (LDTA)assesses distal tibial alignment (normal 86-92°). An abnormality here would indicate an ankle-level deformity, not a distal femoral one.Option D (PDFA)assesses sagittal plane distal femoral alignment (normal 79-87°). While related to the distal femur, it describes flexion/extension deformities, not frontal plane valgus.Option E (NSA)assesses proximal femoral alignment (normal 124-136°). It is unrelated to distal femoral or knee deformities.

Question 152

Topic: Lower Extremity Trauma

A resident is reviewing a long-standing radiograph of a patient with a distal femoral deformity, attempting to apply Paley's standardized nomenclature. They have drawn the mechanical axis of the femur and the knee joint line, creating two supplementary angles at their intersection, as depicted in the diagram below. The resident measures the medial angle as 92° and the lateral angle as 88°.

According to Paley's 'Less Than 90 Degrees' rule, which angle should be formally named and referenced for the distal femur, and what is its normal value?

. A. mMDFA; 92°
. B. mLDFA; 88°
. C. aLDFA; 81°
. D. mMDFA; 88°
. E. aMDFA; 92°

Correct Answer & Explanation

. B. mLDFA; 88°

Explanation

Correct Answer: BPaley's 'Less Than 90 Degrees' rule states that when an axis line intersects a joint line, the angle that is normally less than 90° is chosen for formal naming and reference. For the distal femur, the intersection of the mechanical axis and the knee joint line creates the mMDFA (mechanical Medial Distal Femoral Angle) and the mLDFA (mechanical Lateral Distal Femoral Angle). The normal mLDFA is 88°, while the normal mMDFA is 92°. Therefore, the mLDFA is the standard reference angle.Option A is incorrect because while mMDFA is 92°, it is not the angle chosen by the 'less than 90 degrees' rule.Option C refers to the anatomic axis (aLDFA), which is 81°, but the question specifically refers to the mechanical axis intersection described by the resident's measurements (88° and 92°).Option D is incorrect because mMDFA is normally 92°, not 88°.Option E is incorrect because aMDFA is not the standard reference, and the value is incorrect for the anatomic axis.

Question 153

Topic: Lower Extremity Trauma

A 50-year-old male is scheduled for a high tibial osteotomy (HTO) to correct a varus deformity. During preoperative planning, the surgeon emphasizes the importance of maintaining normal sagittal plane alignment to avoid altering knee kinematics and cruciate ligament tension. The diagram below shows the relevant sagittal plane angles.

Which of the following sagittal plane angles represents the natural posterior slope of the tibial plateau, and what is its normal value?

. A. PDFA; 83°
. B. PPFA; 90°
. C. PPTA; 81°
. D. ADTA; 80°
. E. aJER; 1/5

Correct Answer & Explanation

. C. PPTA; 81°

Explanation

Correct Answer: CThe case explicitly states that the Posterior Proximal Tibial Angle (PPTA) represents the natural posterior slope of the tibial plateau, and its normal value is 81° (range: 77–84°). Maintaining this angle is critical during HTO to avoid altering knee kinematics and cruciate ligament tension.Option A (PDFA) is the Posterior Distal Femoral Angle, which is normally 83°, but it relates to the distal femur, not the proximal tibia.Option B (PPFA) is the Posterior Proximal Femoral Angle, normally 90°, related to the proximal femur.Option D (ADTA) is the Anterior Distal Tibial Angle, normally 80°, related to the distal tibia/ankle joint.Option E (aJER) is the anatomic axis to joint edge ratio, which describes an intersection point, not an angle, and 1/5 is the ratio for the proximal tibia, but it's not the angle itself.

Question 154

Topic: Lower Extremity Trauma

A junior resident is presenting a case of a distal femoral deformity and uses the term 'LDFA' without specifying a prefix. The attending surgeon asks for clarification, emphasizing the importance of precise terminology in deformity correction. The diagram below illustrates the concept of joint orientation.

According to Paley's rules for omitting prefixes, why is it crucial to always specify the prefix for the Distal Femoral Angle?

. A. Because the mechanical and anatomic axes of the femur are collinear in the frontal plane.
. B. Because the normal values for mLDFA and aLDFA are identical.
. C. Because the anatomic axis is rarely used for distal femoral planning.
. D. Because the anatomic and mechanical axes of the femur diverge significantly, and both mLDFA and aLDFA are normally less than 90°.
. E. Because the distal femur is the only segment where the 'less than 90 degrees' rule does not apply.

Correct Answer & Explanation

. D. Because the anatomic and mechanical axes of the femur diverge significantly, and both mLDFA and aLDFA are normally less than 90°.

Explanation

Correct Answer: DThe case explicitly states, 'The ONLY time the prefix MUST be used is for the Distal Femoral Angle. Because the anatomic and mechanical axes of the femur diverge by about 7°, the mLDFA (88°) and aLDFA (81°) are vastly different, yet both are less than 90°. You must always specify mLDFA or aLDFA.'Option A is incorrect; the mechanical and anatomic axes of the femur are NOT collinear; they diverge by about 7°.Option B is incorrect; the normal values for mLDFA (88°) and aLDFA (81°) are different.Option C is incorrect; the anatomic axis (aLDFA) is used, for example, during intramedullary nailing or when the full mechanical axis cannot be visualized.Option E is incorrect; the 'less than 90 degrees' rule applies to the distal femur, but the unique aspect is that both the mechanical and anatomic angles are less than 90°, necessitating the prefix.

Question 155

Topic: Lower Extremity Trauma

A 16-year-old patient presents with a complex multi-planar tibial deformity, including significant procurvatum. During surgical planning, the surgeon needs to understand the sagittal plane relationship between the anatomic axis and the joint lines to accurately place osteotomies and guide wires. The diagram below illustrates the sagittal plane joint orientation angles.

According to Paley's principles regarding the Anatomic Axis to Joint Edge Ratio (aJER) in the sagittal plane, what is the intersection ratio for the proximal tibia and the distal tibia, respectively, measured from the anterior edge?

. A. Proximal Tibia: 1/2; Distal Tibia: 1/3
. B. Proximal Tibia: 1/3; Distal Tibia: 1/5
. C. Proximal Tibia: 1/5; Distal Tibia: 1/2
. D. Proximal Tibia: 1/2; Distal Tibia: 1/5
. E. Proximal Tibia: 1/3; Distal Tibia: 1/2

Correct Answer & Explanation

. C. Proximal Tibia: 1/5; Distal Tibia: 1/2

Explanation

Correct Answer: CThe case details the 'Anatomic Axis to Joint Edge Ratio (aJER)' in the sagittal plane:'Proximal Tibia: The anatomic axis intersects the tibial plateau at an aJER of 1/5 (i.e., very anteriorly).''Distal Tibia: The anatomic axis intersects the ankle joint exactly in the middle, an aJER of 1/2.'Therefore, the correct combination is Proximal Tibia: 1/5 and Distal Tibia: 1/2.Options A, B, D, and E present incorrect combinations or values for the aJER of the proximal and distal tibia.

Question 156

Topic: Lower Extremity Trauma

When utilizing Paley's malalignment test on full-length weight-bearing radiographs, an abnormality in which of the following standard angles definitively localizes a deformity to the distal femur in the coronal plane?

. Mechanical posterior distal femoral angle (mPDFA)
. Mechanical lateral distal femoral angle (mLDFA)
. Mechanical medial proximal tibial angle (mMPTA)
. Joint line convergence angle (JLCA)
. Anatomic mechanical angle (AMA)

Correct Answer & Explanation

. Mechanical lateral distal femoral angle (mLDFA)

Explanation

The mLDFA (normal 85-90 degrees) evaluates the coronal plane alignment of the distal femur. An abnormal mLDFA indicates a distal femoral deformity, distinguishing it from tibial or intra-articular sources of malalignment.

Question 157

Topic: Lower Extremity Trauma

In evaluating a patient with severe bowing of the tibia, two separate diaphyseal CORAs are identified. Which of the following frame constructs is mechanically optimal for simultaneous correction of both deformities without inducing secondary translation?

. A monolateral fixator with a single hinge placed midway between the CORAs
. A standard Taylor Spatial Frame (TSF) with two rings spanning the entire tibia
. A three-ring circular construct with hinges matched to each respective CORA
. An intramedullary nail with blocking screws
. A hybrid fixator with a proximal ring and distal monolateral rail

Correct Answer & Explanation

. A three-ring circular construct with hinges matched to each respective CORA

Explanation

For multi-apical deformities, correcting both apices simultaneously without inducing translation requires an osteotomy and hinge at each CORA. A three-ring construct provides a stable reference segment for each CORA, allowing independent corrections.

Question 158

Topic: Lower Extremity Trauma

In a patient with a retained femoral diaphyseal intramedullary nail and severe end-stage osteoarthritis of the knee, TKA is planned. What is the primary advantage of utilizing computer navigation or robotic assistance in this specific scenario?

. It allows for simultaneous removal of the intramedullary nail through the knee arthrotomy.
. It accurately establishes the mechanical axis without requiring intramedullary canal violation.
. It eliminates the need for soft tissue balancing.
. It relies exclusively on the anatomical axis, which is unaffected by the retained nail.
. It bypasses the need to measure the Joint Line Congruency Angle (JLCA).

Correct Answer & Explanation

. It accurately establishes the mechanical axis without requiring intramedullary canal violation.

Explanation

Retained hardware in the femoral canal precludes the use of standard intramedullary alignment guides. Computer navigation or robotic assistance allows the surgeon to accurately determine the mechanical axis and make precise bone cuts extramedullary.

Question 159

Topic: Lower Extremity Trauma

A 40-year-old male presents with advanced medial compartment osteoarthritis and a mechanical axis deviation (MAD) of 25mm medial to the knee center. Radiographic analysis shows an mLDFA of 94 degrees and an mMPTA of 87 degrees. What is the primary source of the deformity?

. Proximal tibia
. Distal femur
. Intra-articular ligamentous laxity
. Diaphyseal tibial bow
. Diaphyseal femoral bow

Correct Answer & Explanation

. Distal femur

Explanation

The mLDFA is abnormal at 94 degrees (normal is ~87 degrees), indicating a distal femoral varus deformity. The mMPTA is normal (87 degrees), confirming that the proximal tibia is not the primary osseous source of the mechanical axis deviation.

Question 160

Topic: Lower Extremity Trauma

When evaluating the sagittal plane alignment of the tibia for deformity correction or high tibial osteotomy (HTO), the posterior proximal tibial angle (PPTA) is routinely measured. What is the generally accepted normal value for the anatomic PPTA?

. 71 degrees
. 81 degrees
. 91 degrees
. 101 degrees
. 111 degrees

Correct Answer & Explanation

. 81 degrees

Explanation

The normal posterior proximal tibial angle (PPTA) is approximately 81 degrees (range 77 to 84 degrees). This corresponds to the native posterior slope of the tibial plateau, which is roughly 9 degrees relative to the perpendicular of the anatomic axis.

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