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2. Trauma MCQs

Practice Set 153 of 640

This practice set contains high-yield board review questions covering key concepts in 2. Trauma. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 3041

Topic: Lower Extremity Trauma

When planning a high tibial osteotomy (HTO) for medial compartment osteoarthritis with a varus deformity, the mechanical axis is typically shifted slightly laterally. According to the Paley method and classic literature, the target correction point (the Fujisawa point) is located at approximately what percentage of the tibial plateau width from the medial edge?

. 25%
. 50%
. 62%
. 85%
. 100%

Correct Answer & Explanation

. 62%

Explanation

The Fujisawa point is located at approximately 62% to 62.5% of the mediolateral width of the tibial plateau, measured from the medial edge. This provides 3 to 5 degrees of mechanical valgus, effectively offloading the medial compartment.

Question 3042

Topic: 2. Trauma

During a large-angle medial opening wedge HTO, the intact fibula acts as a lateral tether. Which of the following best describes the consequence of failing to release the proximal tibiofibular joint or osteotomize the fibular shaft during such a correction?

. Increased risk of nonunion at the tibial osteotomy
. Unintentional increase in posterior tibial slope
. Medial translation of the distal tibial fragment
. High incidence of common peroneal nerve palsy
. Excessive valgus overcorrection

Correct Answer & Explanation

. Unintentional increase in posterior tibial slope

Explanation

The fibular head is located posterolaterally. If left intact during a large medial opening wedge HTO, it tethers the posterolateral tibia, causing the anterior gap to open more than the posterior gap, unintentionally increasing the posterior tibial slope.

Question 3043

Topic: Lower Extremity Trauma

A 70-year-old female with end-stage medial compartment osteoarthritis and a severe varus knee deformity is being evaluated for a high tibial osteotomy. Radiographs show significant medial joint space narrowing and lateral joint gapping. Her Joint Line Congruency Angle (JLCA) is measured at 7 degrees. Based on the Paley principles, what does this specific JLCA measurement primarily indicate?

. A. The deformity is exclusively located in the distal femur, requiring a distal femoral osteotomy.
. B. The knee joint lines are perfectly parallel, indicating balanced soft tissues.
. C. There is significant joint incongruity, likely due to asymmetric cartilage loss and/or lateral ligamentous laxity.
. D. The mechanical axis passes precisely through the center of the knee joint.
. E. The patient has a physiological varus alignment, and no surgical intervention is warranted.

Correct Answer & Explanation

. C. There is significant joint incongruity, likely due to asymmetric cartilage loss and/or lateral ligamentous laxity.

Explanation

Correct Answer: CThe case content defines the Joint Line Congruency Angle (JLCA) as the angle between tangential lines to the distal femur and proximal tibia articular surfaces. A normal JLCA is 0° to 2°, indicating nearly parallel joint lines and competent ligaments. An increased angle (>2°), such as the 7 degrees in this patient, is a 'massive red flag' for severe joint incongruity, asymmetric cartilage loss (medial collapse), and/or significant lateral ligamentous laxity. This finding is highly predictive of a dynamic varus thrust during gait and indicates a complex reconstructive challenge.Option A is incorrectbecause the JLCA primarily assesses joint line parallelism and soft tissue competence, not the specific location of the bony deformity (which would be determined by angles like mLDFA or MPTA). While a DFO might be needed, the JLCA itself doesn't pinpoint the bony segment.Option B is incorrectbecause a JLCA of 7 degrees is significantly abnormal and indicates severe joint incongruity, meaning the joint lines are far from parallel.Option D is incorrectbecause the JLCA measures joint line parallelism, not the position of the mechanical axis relative to the knee center (which is the Mechanical Axis Deviation, MAD).Option E is incorrectbecause a JLCA of 7 degrees is pathologically high, indicating severe deformity and instability, far from physiological alignment, and strongly warrants surgical consideration.

Question 3044

Topic: Lower Extremity Trauma

A 30-year-old male presents with a progressive varus deformity of his right lower extremity. A full-length standing radiograph is obtained for deformity analysis. The surgeon measures the angle formed between the mechanical axis of the tibia and the tangent to the proximal tibial articular surface, as shown in the diagram. This angle is found to be 80 degrees. Based on the Paley principles and the provided image, what does this measurement most accurately indicate?

. A. The deformity is located in the distal femur, requiring a distal femoral osteotomy.
. B. The patient has a normal physiological alignment of the proximal tibia.
. C. The patient has tibia vara, with the deformity located in the proximal tibia.
. D. The knee joint has significant lateral ligamentous laxity.
. E. The mechanical axis of the entire limb is in valgus alignment.

Correct Answer & Explanation

. C. The patient has tibia vara, with the deformity located in the proximal tibia.

Explanation

Correct Answer: CThe diagram (ch_278_fig_847647.webp) illustrates the Medial Proximal Tibial Angle (MPTA). The case content defines the MPTA as determining proximal tibial coronal alignment, with a normal range of 85° to 90° (average 87°). A low MPTA (<85°), such as the 80 degrees measured in this patient, definitively indicates tibia vara. This specific angular change proves that the deformity is located within the proximal tibia itself, guiding the surgeon towards a High Tibial Osteotomy (HTO) for correction.Option A is incorrectbecause an abnormal MPTA specifically points to a deformity in the proximal tibia, not the distal femur. Distal femoral deformities are assessed by the mLDFA.Option B is incorrectbecause a normal MPTA is 85-90 degrees. An MPTA of 80 degrees is pathologically low, indicating a varus deformity of the proximal tibia.Option D is incorrectbecause while lateral ligamentous laxity can be associated with varus knees, the MPTA directly measures bony alignment of the proximal tibia, not soft tissue laxity. JLCA is used for joint line congruity and ligamentous laxity.Option E is incorrectbecause tibia vara (low MPTA) contributes to overall limb varus, not valgus alignment. The mechanical axis would be shifted medially.

Question 3045

Topic: Lower Extremity Trauma

A 40-year-old patient undergoes a full-length standing radiograph as part of a routine orthopedic evaluation. The mechanical axis of the lower limb is measured and found to pass approximately 8 mm medial to the center of the tibial plateau. Based on the Paley principles of deformity analysis, what does this measurement indicate?

. A. The patient has a pathological varus deformity requiring immediate intervention.
. B. The patient has a pathological valgus deformity, as the axis should be lateral to the knee center.
. C. This represents a normal, physiological mechanical axis deviation (MAD).
. D. The patient has severe lateral compartment overloading.
. E. The measurement is indicative of a fixed flexion deformity of the knee.

Correct Answer & Explanation

. C. This represents a normal, physiological mechanical axis deviation (MAD).

Explanation

Correct Answer: CThe case content explicitly defines the normal Mechanical Axis Deviation (MAD) for a healthy lower limb: 'In a normal, healthy lower limb, the mechanical axis does not pass perfectly through the dead center of the knee. Instead, it passes slightly medial to the center of the knee joint, creating a physiologic Mechanical Axis Deviation (MAD) of approximately 8 mm medial to the center of the tibial plateau.' This slight medial deviation results in the normal, inherent adduction moment and physiological load distribution across the knee.Option A is incorrectbecause 8 mm medial deviation is the normal physiological MAD, not a pathological varus deformity.Option B is incorrectbecause the normal axis is slightly medial, not lateral. A lateral deviation would indicate a valgus deformity.Option D is incorrectbecause this normal MAD results in the physiological load distribution (68% medial, 32% lateral), not severe lateral compartment overloading. Lateral overloading occurs in valgus deformities.Option E is incorrectbecause MAD measures coronal plane alignment, not sagittal plane deformities like fixed flexion.

Question 3046

Topic: 2. Trauma

A surgeon is planning a complex osteotomy for a patient with a long-standing angular deformity of the femur. The preoperative planning involves meticulous identification of the Center of Rotation of Angulation (CORA). The image below shows a foot with a potential deformity. What is the most crucial advantage of performing the corrective osteotomy precisely at the CORA?

. It minimizes the risk of nonunion at the osteotomy site.
. It allows for pure angular correction without inducing an unwanted translation of the bone fragments.
. It reduces the overall operative time and blood loss.
. It facilitates the application of external fixation devices.
. It ensures the preservation of the periosteal blood supply.

Correct Answer & Explanation

. It allows for pure angular correction without inducing an unwanted translation of the bone fragments.

Explanation

Correct Answer: BThe case explicitly states that 'Identifying the CORA is the most crucial step in preoperative planning. It dictates the precise level and orientation of the corrective osteotomy. An osteotomy performed exactly at the CORA allows for pure angular correction, restoring the limb's mechanical axis without inducing an unwanted and problematic shift (translation) of the bone fragments.' The other options, while potentially desirable surgical outcomes, are not the primary and unique advantage of performing an osteotomy specifically at the CORA for angular deformity correction.

Question 3047

Topic: Lower Extremity Trauma

A 60-year-old patient presents with the clinical appearance shown in the image, consistent with genu varum. Full-length weight-bearing radiographs are obtained for deformity analysis. The measurements reveal a mechanical Lateral Distal Femoral Angle (mLDFA) of 88° and a Medial Proximal Tibial Angle (MPTA) of 80°. Based on Paley's principles, where is the primary frontal plane deformity located?

. Distal femur
. Proximal tibia
. Ankle joint
. Midfoot
. Knee joint (intra-articular)

Correct Answer & Explanation

. Proximal tibia

Explanation

Correct Answer: BAccording to the provided table, the normal range for mLDFA is 85-90°, and for MPTA is 85-90°. An mLDFA of 88° falls within the normal range, indicating no significant frontal plane deformity in the distal femur. However, an MPTA of 80° is less than 85°, which indicates tibial varus. Therefore, the primary frontal plane deformity is located in the proximal tibia. The clinical appearance of genu varum is consistent with a proximal tibial varus. Option E (Knee joint intra-articular) would be suggested by an abnormal JLCA, which is not provided here.

Question 3048

Topic: 2. Trauma

A 30-year-old male sustains a distal femur fracture treated with a retrograde intramedullary nail. Postoperatively, his mechanical lateral distal femoral angle (mLDFA) is measured at 98 degrees. What specific deformity has been inadvertently created?

. Distal femoral valgus
. Distal femoral varus
. Distal femoral procurvatum
. Distal femoral recurvatum
. Normal alignment has been restored

Correct Answer & Explanation

. Distal femoral varus

Explanation

The normal mLDFA is approximately 87 degrees (range 85-90). An mLDFA of 98 degrees indicates that the distal articular surface is angled excessively varus relative to the mechanical axis of the femur.

Question 3049

Topic: 2. Trauma

A patient presents with a malunited proximal tibia fracture. The posterior proximal tibial angle (PPTA) is measured on the lateral radiograph as 70 degrees. Assuming the normal value is 81 degrees, what sagittal plane deformity is present?

. Procurvatum deformity
. Recurvatum deformity
. Anterior translation of the diaphysis
. Posterior translation of the diaphysis
. Normal sagittal alignment

Correct Answer & Explanation

. Procurvatum deformity

Explanation

The normal PPTA is 81 degrees, reflecting a normal posterior slope. A decreased PPTA (e.g., 70 degrees) indicates that the proximal articular surface is tilted more posteriorly relative to the shaft, which represents a procurvatum (apex anterior) deformity.

Question 3050

Topic: 2. Trauma

What is the primary biomechanical and clinical advantage of the "lengthening and then nailing" (LATN) technique compared to traditional Ilizarov external fixation lengthening?

. It allows for immediate unprotected full weight-bearing
. It significantly reduces the external fixation index (EFI)
. It completely eliminates the risk of deep infection
. It prevents the development of joint contractures
. It requires only a single surgical intervention

Correct Answer & Explanation

. It significantly reduces the external fixation index (EFI)

Explanation

The LATN technique utilizes an external fixator for the distraction phase and an intramedullary nail for the consolidation phase. This dramatically reduces the external fixation index (EFI), freeing the patient from the frame much earlier than traditional methods.

Question 3051

Topic: Lower Extremity Trauma

A 45-year-old female presents with medial knee pain. Radiographs reveal a mechanical Medial Proximal Tibial Angle (mMPTA) of 80 degrees and a mechanical Lateral Distal Femoral Angle (mLDFA) of 88 degrees. What is the primary source of her varus deformity?

. The distal femur
. The proximal tibia
. The knee joint line soft tissues
. Extra-articular femoral shaft bowing
. Both the femur and tibia contribute equally

Correct Answer & Explanation

. The proximal tibia

Explanation

The normal mMPTA is 87 degrees (range 85-90). An mMPTA of 80 degrees indicates a significant varus deformity originating intrinsically in the proximal tibia. The mLDFA of 88 degrees is within normal limits, ruling out a femoral contribution.

Question 3052

Topic: 2. Trauma

In circular external fixation (Ilizarov methodology), what is the primary biomechanical effect of increasing the tension on the transfixion wires?

. Decreases overall axial stiffness
. Increases axial and bending stiffness
. Decreases bending stiffness across the fracture site
. Increases translational shear forces at the osteotomy
. Reduces the biological capacity for bone regenerate formation

Correct Answer & Explanation

. Increases axial and bending stiffness

Explanation

Properly tensioning the transfixion wires in a circular frame significantly increases both the axial and bending stiffness of the construct. This rigid yet elastic stability is essential for proper force transmission and favorable bone regenerate formation during distraction osteogenesis.

Question 3053

Topic: 2. Trauma

A 40-year-old female presents with post-traumatic valgus malunion of the tibia. Her Joint Line Convergence Angle (JLCA) is measured at 6 degrees, opening medially. The surgeon suspects medial collateral ligament (MCL) laxity. If a standard osteotomy corrects the bony mMPTA to normal without addressing the JLCA, what will be the effect on the overall mechanical axis deviation (MAD)?

. The MAD will be perfectly corrected to 0 mm
. The MAD will remain in valgus due to the joint laxity
. The MAD will overcorrect into varus
. The JLCA will automatically normalize
. The mMPTA will spontaneously change to compensate

Correct Answer & Explanation

. The MAD will remain in valgus due to the joint laxity

Explanation

The JLCA represents intra-articular deformity or ligamentous laxity. If an abnormal JLCA is not accounted for in the preoperative planning, correcting only the bony angles will leave a residual mechanical axis deviation in valgus.

Question 3054

Topic: Lower Extremity Trauma

A patient undergoes correction of a severe procurvatum deformity of the distal femur. The normal mechanical Posterior Distal Femoral Angle (mPDFA) referenced during planning is approximately:

. 83 degrees
. 90 degrees
. 79 degrees
. 88 degrees
. 95 degrees

Correct Answer & Explanation

. 83 degrees

Explanation

The normal mechanical Posterior Distal Femoral Angle (mPDFA) in the sagittal plane is approximately 83 degrees. Deviations from this angle indicate a procurvatum or recurvatum deformity at the distal femur.

Question 3055

Topic: 2. Trauma

In Taylor Spatial Frame (TSF) software, the chronic program is typically selected for which of the following scenarios?

. Acute intraoperative correction of a deformity
. Gradual correction of a stiff nonunion or malunion over several weeks
. Immediate reduction of an acute fracture
. Lengthening of a congenitally short limb without angular deformity
. Acute compression of an arthrodesis site

Correct Answer & Explanation

. Gradual correction of a stiff nonunion or malunion over several weeks

Explanation

The chronic program in hexapod circular fixators is designed for gradual, multi-planar correction of a deformity over time, accommodating soft tissue stretching limits and the rate of bone regenerate formation.

Question 3056

Topic: Lower Extremity Trauma

A patient presents with a severe valgus deformity of the knee. Radiographic analysis reveals a mechanical lateral distal femoral angle (mLDFA) of 78 degrees and a normal mechanical medial proximal tibial angle (mMPTA) of 87 degrees. Where is the primary center of deformity?

. Proximal tibia
. Distal femur
. Intra-articular knee joint
. Proximal femur
. Diaphysis of the tibia

Correct Answer & Explanation

. Distal femur

Explanation

The normal mLDFA is approximately 87-88 degrees. An mLDFA of 78 degrees indicates a significant valgus deformity originating in the distal femur. The normal mMPTA confirms the tibia is not the primary source of the valgus.

Question 3057

Topic: Lower Extremity Trauma

A patient with a tibial shaft deformity has an osteotomy performed strictly following Paley's Rule 3. The hinge is placed at the osteotomy site, which is located 4 cm away from the CORA. What is the expected biomechanical consequence?

. Perfect alignment of the mechanical axis without translation.
. Pure translation of the bone ends.
. Creation of a secondary translation deformity.
. Complete failure of regenerate bone formation.
. Immediate correction of the joint line convergence angle.

Correct Answer & Explanation

. Creation of a secondary translation deformity.

Explanation

Paley's Rule 3 states that if the osteotomy and the hinge are both separated from the CORA, angular correction will result in a secondary translation deformity. This leads to a zig-zag deformity and fails to collinearly align the proximal and distal mechanical axes.

Question 3058

Topic: 2. Trauma

What is the physiological purpose of the 5-7 day 'latency period' following a corticotomy before initiating distraction osteogenesis?

. To allow the soft tissue envelope to completely heal and seal the pin sites.
. To permit the initial hematoma to organize and mesenchymal stem cells to differentiate.
. To prevent acute compartment syndrome by reducing intraosseous pressure.
. To allow time for the patient to learn how to turn the struts on the spatial frame.
. To ensure that the corticotomy site has fully united before pulling it apart.

Correct Answer & Explanation

. To permit the initial hematoma to organize and mesenchymal stem cells to differentiate.

Explanation

A latency period of 5-7 days allows for the resolution of acute inflammation and the organization of the fracture hematoma. This permits mesenchymal stem cells to migrate and differentiate, establishing the vital cellular machinery required for osteogenesis.

Question 3059

Topic: Lower Extremity Trauma

When evaluating a patient's standing AP radiograph for mechanical axis deviation (MAD), the Joint Line Convergence Angle (JLCA) is measured at 6 degrees converging medially (normal is 0-2 degrees). What does this finding indicate?

. Normal physiological alignment.
. A purely extra-articular diaphyseal deformity.
. Intra-articular deformity or ligamentous laxity causing joint space opening.
. A severe fixed valgus deformity of the distal femur.
. An excessive mechanical medial proximal tibial angle.

Correct Answer & Explanation

. Intra-articular deformity or ligamentous laxity causing joint space opening.

Explanation

The JLCA evaluates the parallelism of the knee joint lines. An abnormally high JLCA (e.g., 6 degrees) implies that the mechanical axis deviation is partly or completely due to intra-articular causes, such as lateral cartilage loss or lateral collateral ligament laxity.

Question 3060

Topic: Lower Extremity Trauma

A 25-year-old female presents with bilateral knee pain and clinical genu valgum. Full-length standing radiographs reveal a mechanical axis deviation (MAD) of 25 mm laterally on the right leg. The surgeon measures joint orientation angles to isolate the source of the deformity. Which of the following values strongly indicates that the femur is the primary source of her valgus deformity?

. Mechanical lateral distal femoral angle (mLDFA) of 81 degrees.
. Mechanical medial proximal tibial angle (mMPTA) of 88 degrees.
. Mechanical lateral distal femoral angle (mLDFA) of 95 degrees.
. Mechanical medial proximal tibial angle (mMPTA) of 95 degrees.
. Anatomic lateral distal femoral angle (aLDFA) of 81 degrees.

Correct Answer & Explanation

. Mechanical lateral distal femoral angle (mLDFA) of 81 degrees.

Explanation

The normal mLDFA is approximately 87-88 degrees. An mLDFA significantly less than 85 degrees (such as 81 degrees) indicates a valgus deformity of the distal femur. An mLDFA of 95 degrees would indicate femoral varus.

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