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Lower Extremity Trauma MCQs

Practice Set 15 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 281

Topic: Lower Extremity Trauma

A 60-year-old patient presents with a severe valgus deformity of the distal femur and a noticeable limb length discrepancy (lengthening). The surgeon plans a varus-producing distal femoral osteotomy to correct the valgus and simultaneously shorten the limb. Based on the Paley principles of wedge mechanics, where should the Axis of Correction of Angulation (ACA) be strategically placed relative to the CORA and the deformity's cortex to achieve this outcome, as illustrated in the diagram?

. At the CORA, on the convex cortex, resulting in a neutral wedge.
. On the convex cortex, distal to the CORA, resulting in an opening wedge.
. On the concave cortex, proximal to the CORA, resulting in a closing wedge.
. On the concave cortex, distal to the CORA, resulting in an opening wedge.
. On the convex cortex, proximal to the CORA, resulting in a closing wedge.

Correct Answer & Explanation

. On the concave cortex, proximal to the CORA, resulting in a closing wedge.

Explanation

Correct Answer: CThe text and the provided diagram (ch_45_fig_b9e598.webp) illustrate wedge mechanics. To achieve a closing wedge osteotomy (which shortens the bone), the ACA (hinge) must be placed on theconcave cortex. For a valgus deformity of the distal femur, the lateral side is convex and the medial side is concave. Therefore, to create a closing wedge to correct valgus and shorten, the hinge (ACA) is placed on the medial (concave) cortex, away from the CORA.Option Adescribes a neutral wedge, which does not change length.Options B and Ddescribe an opening wedge, which lengthens the bone.Option Eis incorrect; placing the ACA on the convex cortex would result in an opening wedge (lengthening) if placed away from the CORA, or a neutral wedge if at the CORA. A closing wedge requires the hinge on the concave side.

Question 282

Topic: Lower Extremity Trauma

A 70-year-old patient presents with chronic knee pain. Full-length weight-bearing radiographs show a normal Mechanical Axis Deviation (MAD), and both the mLDFA (87°) and MPTA (88°) are within normal limits. However, the Joint Line Convergence Angle (JLCA) is measured at 5°. What is the MOST likely interpretation of these findings according to the Paley principles?

. The patient has a significant varus deformity originating from the proximal tibia.
. The patient has a significant valgus deformity originating from the distal femur.
. The patient has an overall well-aligned limb, and the pain is likely non-orthopedic.
. The patient has significant intra-articular pathology, such as asymmetric cartilage loss or ligamentous laxity.
. The patient has a multiapical deformity requiring complex planning.

Correct Answer & Explanation

. The patient has significant intra-articular pathology, such as asymmetric cartilage loss or ligamentous laxity.

Explanation

Correct Answer: DThe text defines the JLCA as measuring 'the angle between the distal femoral and proximal tibial joint lines. An increased JLCA suggests intra-articular pathology, such as significant asymmetric cartilage loss or ligamentous laxity allowing the joint to pathologically 'gap open.'' A normal JLCA is 0° to 2°. A JLCA of 5° is significantly elevated, indicating a problem within the joint itself, even if the overall limb alignment (MAD) and bone segment angles (mLDFA, MPTA) are normal. This suggests that the joint space itself is compromised, likely due to cartilage wear or ligamentous instability.Option A and Bare incorrect because the mLDFA and MPTA are within normal limits, ruling out significant bony varus or valgus deformities in the femur or tibia.Option Cis incorrect; while the overall limb alignment is normal, the elevated JLCA points to a specific orthopedic pathology within the knee joint, which is a significant finding.Option Eis incorrect; a multiapical deformity would typically manifest with abnormal mLDFA and/or MPTA, which are normal in this case. The isolated elevated JLCA points to an intra-articular issue.

Question 283

Topic: Lower Extremity Trauma

When evaluating lower extremity alignment, a malalignment test is performed on a full-length weight-bearing radiograph. The Mechanical Axis Deviation (MAD) is found to be 30 mm medial to the center of the knee joint. The mechanical lateral distal femoral angle (mLDFA) is 97 degrees, and the mechanical medial proximal tibial angle (mMPTA) is 87 degrees. What is the primary source of the patient's deformity?

. Proximal tibial varus
. Proximal tibial valgus
. Distal femoral varus
. Distal femoral valgus
. Intra-articular ligamentous laxity

Correct Answer & Explanation

. Distal femoral varus

Explanation

The normal mLDFA is approximately 87 degrees (range 85-90) and the normal mMPTA is 87 degrees. An mLDFA of 97 degrees indicates an abnormal varus deformity in the distal femur, which correlates with the medial MAD.

Question 284

Topic: Lower Extremity Trauma

In evaluating sagittal plane deformity of the femur, the mechanical posterior distal femoral angle (mPDFA) is measured. If the mPDFA is found to be 96 degrees (normal ~83 degrees), what specific deformity does this indicate?

. Distal femoral recurvatum
. Distal femoral procurvatum
. Proximal femoral varus
. Proximal femoral valgus
. Distal femoral flexion deformity

Correct Answer & Explanation

. Distal femoral procurvatum

Explanation

The normal mPDFA is 83 degrees. An increased mPDFA means the distal segment is flexed relative to the proximal shaft, which creates an anterior bowing or procurvatum deformity of the distal femur.

Question 285

Topic: Lower Extremity Trauma

A 38-year-old male is 8 weeks into a tibial deformity correction using a circular ring fixator. He reports mild pain, erythema, and a small amount of serous drainage at a single medial pin site. The pin is not loose, and there are no systemic symptoms. What is the most appropriate initial management?

. Immediate removal of the pin and application of a new pin in a different plane
. Intravenous antibiotics and surgical debridement of the pin tract
. Oral antibiotics and intensified local pin site care
. Discontinuation of any frame adjustments until the drainage stops
. Immediate frame removal and conversion to an intramedullary nail

Correct Answer & Explanation

. Oral antibiotics and intensified local pin site care

Explanation

This represents a superficial pin site infection (Checketts-burns Grade 1-2). In the absence of pin loosening or systemic signs, the standard initial treatment is oral antibiotics and aggressive local pin site care.

Question 286

Topic: Lower Extremity Trauma

A 45-year-old female presents with bilateral knee pain. Standing full-length radiographs reveal a medial mechanical axis deviation (MAD) of 25 mm bilaterally. Analysis of joint orientation angles demonstrates a mechanical lateral distal femoral angle (mLDFA) of 96 degrees, a mechanical medial proximal tibial angle (mMPTA) of 87 degrees, and a joint line convergence angle (JLCA) of 1 degree. Where is the primary source of the deformity?

. Proximal tibia
. Distal femur
. Intra-articular knee joint
. Distal tibia
. Combined distal femur and proximal tibia

Correct Answer & Explanation

. Distal femur

Explanation

The normal mLDFA is 88 degrees (range 85-90). An mLDFA of 96 degrees indicates a significant varus deformity of the distal femur. The mMPTA (normal 87) and JLCA (normal 0-2) are within normal physiological limits.

Question 287

Topic: Lower Extremity Trauma

A patient presents with a varus deformity of the lower extremity. Radiographic evaluation reveals a mechanical lateral distal femoral angle (mLDFA) of 88 degrees, a mechanical medial proximal tibial angle (mMPTA) of 79 degrees, and a joint line convergence angle (JLCA) of 2 degrees. What is the primary source of the varus deformity?

. Distal femur
. Proximal tibia
. Intra-articular knee joint
. Proximal femur
. Diaphyseal femur

Correct Answer & Explanation

. Proximal tibia

Explanation

The normal mMPTA is approximately 87 degrees. An mMPTA of 79 degrees indicates a proximal tibial varus deformity. The mLDFA (normal 88 degrees) and JLCA (normal 0-2 degrees) are within normal limits.

Question 288

Topic: Lower Extremity Trauma

A 40-year-old patient presents with a complex multi-apical femoral deformity. The surgeon is using Paley's geometric methodology for preoperative planning. The text emphasizes that the goal of this methodology is not merely to make the bone look straight on an X-ray. What is the primary biomechanical imperative of restoring the mechanical axis in frontal plane deformity correction?

. A. To ensure optimal bone healing at the osteotomy site.
. B. To minimize surgical blood loss during the procedure.
. C. To restore the mechanical axis so that it passes through the center of the knee joint, thereby normalizing joint reactive forces.
. D. To facilitate easier insertion of intramedullary nails.
. E. To prevent nerve and vascular injury during surgical correction.

Correct Answer & Explanation

. C. To restore the mechanical axis so that it passes through the center of the knee joint, thereby normalizing joint reactive forces.

Explanation

Correct Answer: CThe text explicitly states: 'The goal of Paley's methodology is not simply to make the bone look straight on an X-ray, but to restore the mechanical axis so that it passes through the center of the knee joint, thereby normalizing joint reactive forces and preserving the longevity of the native cartilage.' This is the fundamental biomechanical reason for precise alignment correction.Incorrect Options:A. To ensure optimal bone healing at the osteotomy site:While good alignment contributes to stable fixation and thus healing, the primary biomechanical imperative ofrestoring the mechanical axisis about joint load, not directly about osteotomy healing itself.B. To minimize surgical blood loss during the procedure:Blood loss is a general surgical concern and not the primary biomechanical goal of restoring the mechanical axis.D. To facilitate easier insertion of intramedullary nails:While understanding the anatomic axis is crucial for IM nailing, theprimary biomechanical imperativeof restoring themechanical axisis about joint load distribution, not the ease of implant insertion.E. To prevent nerve and vascular injury during surgical correction:This is a critical aspect of surgical safety, but it is not the primary biomechanical goal of restoring the mechanical axis in the context of joint load and longevity.

Question 289

Topic: Lower Extremity Trauma

A 55-year-old patient presents with severe right knee osteoarthritis and a significant varus deformity. A full-length standing radiograph is performed as part of the Malalignment Test, shown below. The mechanical axis (dotted line) passes far medial to the knee. Measurements reveal an mLDFA of 109° and an MPTA of 87°. Based on these findings, where is the primary source of the deformity localized?

. Primarily in the proximal tibia, with a normal distal femur.
. Equally distributed between the distal femur and proximal tibia.
. Primarily in the distal femur, with a normal proximal tibia.
. In the proximal femur, requiring a subtrochanteric osteotomy.
. In the ankle joint, necessitating an ankle fusion.

Correct Answer & Explanation

. Primarily in the distal femur, with a normal proximal tibia.

Explanation

Correct Answer: CThe case describes the Malalignment Test as the diagnostic starting point. The normal range for the Mechanical Lateral Distal Femoral Angle (mLDFA) is 85°–90°, and for the Medial Proximal Tibial Angle (MPTA) is 85°–90°. In this patient, the mLDFA is 109°, which is significantly outside the normal range, indicating a deformity in the distal femur. The MPTA is 87°, which is within the normal range, indicating that the proximal tibia is normally aligned. Therefore, the primary problem is definitively localized to the femur, specifically the distal femur, as the mLDFA is abnormal while the MPTA is normal.Option A is incorrect because the MPTA is normal, ruling out a primary tibial deformity. Option B is incorrect because the deformity is clearly localized to the femur based on the abnormal mLDFA and normal MPTA. Option D is incorrect; while the deformity is femoral, the mLDFA specifically points to the distal femur, not necessarily the proximal femur, without further proximal femoral angle measurements. Option E is incorrect as the measurements relate to the knee and femur/tibia, not the ankle joint.

Question 290

Topic: Lower Extremity Trauma

A surgeon is planning an intramedullary (IM) nail fixation for a multiapical femoral deformity using the anatomic axis planning method. As part of reconstructing normalcy with joint-referenced lines, the surgeon needs to draw the distal anatomic axis. Which of the following accurately describes how the distal anatomic axis is drawn in this context?

. From the center of the knee joint, drawn proximally at the normal mLDFA of 87°.
. From a point 10 mm lateral to the center of the knee joint, drawn proximally at the normal aLDFA of 81°.
. From a point 10 mm medial to the center of the knee joint, drawn proximally at the normal aLDFA of 81°.
. From the center of the ankle plafond, extended proximally through the knee joint.
. Parallel to the proximal mechanical axis, offset by 7°.

Correct Answer & Explanation

. From a point 10 mm medial to the center of the knee joint, drawn proximally at the normal aLDFA of 81°.

Explanation

Correct Answer: CThe case describes anatomic axis planning for a multiapical femur. For the distal femur, it states: 'The distal anatomic axis is drawn from a specific point that is10 mm medialto the center of the knee joint. This 10 mm offset is known as the anatomic Joint Center Distance (aJCD), accounting for the natural valgus of the distal femur. This line is drawn proximally at the normalaLDFA of 81°.' This method ensures the final correction restores normal joint orientation relative to the anatomic axis, which is crucial for IM nailing.Option A describes drawing the distal mechanical axis when the tibia is abnormal, not the distal anatomic axis. Option B incorrectly states 10 mm lateral; it should be 10 mm medial. Option D describes the overall mechanical axis, not a specific anatomic reference for the distal femur. Option E describes the relationship between mechanical and anatomic axes (AMA), not how to draw the distal anatomic axis from the knee joint.

Question 291

Topic: Lower Extremity Trauma

A 38-year-old male presents with a long-standing, progressive genu varum deformity following a childhood physeal injury. Preoperative planning reveals a single, well-defined angular deformity in the distal femur. According to the Paley method, which of the following statements accurately describes the Center of Rotation of Angulation (CORA) in this patient's simple deformity?

. The CORA is the point where the mechanical axis of the entire limb intersects the joint line of the knee.
. The CORA represents the midpoint of the osteotomy site, regardless of the deformity's apex.
. The CORA is the geometric point where the proximal and distal axes of the deformed bone intersect, dictating the optimal osteotomy level.
. The CORA is primarily used to calculate the Mechanical Axis Deviation (MAD) in millimeters.
. The CORA is an infinite number of points along the curve of a bowing deformity.

Correct Answer & Explanation

. The CORA is the geometric point where the proximal and distal axes of the deformed bone intersect, dictating the optimal osteotomy level.

Explanation

Correct Answer: CThe Center of Rotation of Angulation (CORA) is defined as the exact point in two-dimensional space where the proximal and distal axes (either anatomical or mechanical) of a deformed bone intersect. Its precise location is the single most critical step in deformity planning, as it dictates the optimal level of the osteotomy and the placement of the hinge or Axis of Correction of Angulation (ACA). In a simple, uniapical deformity, there is a single CORA.Option A is incorrectbecause the mechanical axis of the limb intersects the knee joint, but this intersection is not the definition of a CORA. The CORA is specific to the deformed bone segment.Option B is incorrectbecause the CORA dictates the optimal osteotomy level, not the other way around. Placing an osteotomy at the CORA minimizes iatrogenic translation.Option D is incorrectbecause the Mechanical Axis Deviation (MAD) is calculated by drawing the Mikulicz line and assessing its relationship to the knee joint, not directly by the CORA. The CORA helps localize the deformity, while MAD quantifies the overall limb malalignment.Option E is incorrectbecause while bowing deformities do have an infinite number of CORAs along a curve, this statement describes a complex bowing deformity, not a simple, uniapical angular deformity as described in the vignette. For a simple angular deformity, there is a single CORA.

Question 292

Topic: Lower Extremity Trauma

A 25-year-old male presents with a complex lower extremity deformity. During preoperative planning, the surgeon measures the Joint Line Convergence Angle (JLCA) and finds it to be 5 degrees. According to the Paley method, what is the primary clinical significance of this finding?

. It indicates a normal knee joint alignment, and the deformity is purely bony.
. It suggests significant ligamentous laxity or unilateral cartilage loss within the knee joint.
. It confirms an isolated distal femoral varus deformity.
. It is the most accurate angle for planning intramedullary nailing.
. It is used to determine the Mechanical Axis Deviation (MAD) directly.

Correct Answer & Explanation

. It suggests significant ligamentous laxity or unilateral cartilage loss within the knee joint.

Explanation

Correct Answer: BThe Joint Line Convergence Angle (JLCA) normally ranges from 0° to 2°, with an average of 0° to 1°. A JLCA greater than 2° (such as 5° in this case) indicates intra-articular issues, specifically suggesting ligamentous laxity or unilateral cartilage loss. As per the surgical pearls, always measure the JLCA first, as a high JLCA can create a 'pseudo-deformity' or exacerbate a bony deformity, requiring the surgeon to calculate the bony deformity independent of the joint laxity.Option A is incorrectbecause a JLCA of 5° is significantly outside the normal range (0-2°) and indicates an intra-articular problem, not normal knee joint alignment.Option C is incorrectbecause the JLCA indicates an intra-articular issue, not specifically an isolated distal femoral varus deformity. Other angles like mLDFA would be used to assess distal femoral alignment.Option D is incorrectbecause anatomic angles like aLDFA and MPFA are preferred for planning intramedullary nailing, not the JLCA.Option E is incorrectbecause the MAD is determined by drawing the Mikulicz line from the femoral head to the ankle and assessing its relationship to the knee joint, not directly by the JLCA.

Question 293

Topic: Lower Extremity Trauma

A 50-year-old patient presents with a history of a malunited femoral shaft fracture. The surgeon is planning a corrective osteotomy using an intramedullary nail. Which of the following joint orientation angles is most relevant for defining distal femoral alignment when planning for intramedullary nailing?

. Mechanical Lateral Distal Femoral Angle (mLDFA)
. Medial Proximal Tibial Angle (MPTA)
. Anatomic Lateral Distal Femoral Angle (aLDFA)
. Lateral Proximal Femoral Angle (LPFA)
. Joint Line Convergence Angle (JLCA)

Correct Answer & Explanation

. Anatomic Lateral Distal Femoral Angle (aLDFA)

Explanation

Correct Answer: CThe text explicitly states, 'When planning for intramedullary nails, anatomic angles (aLDFA, MPFA) are your best friends.' The Anatomic Lateral Distal Femoral Angle (aLDFA) is the anatomic equivalent of the mLDFA and is highly useful for intramedullary (IM) nailing because it relates the distal femoral joint line to the anatomic axis (mid-diaphyseal line), which is the trajectory of an IM nail. Its normal range is 79° to 83° (average 81°).Option A is incorrectbecause the mLDFA is a mechanical angle, generally preferred for plates or external fixators, as it relates to the mechanical axis, not the anatomic axis used by IM nails.Option B is incorrectbecause the MPTA defines proximal tibial alignment, not distal femoral alignment.Option D is incorrectbecause the LPFA defines proximal femoral alignment based on the mechanical axis, not distal femoral alignment or the anatomic axis relevant for IM nailing.Option E is incorrectbecause the JLCA indicates intra-articular issues and is not directly used for defining bony alignment for IM nailing.

Question 294

Topic: Lower Extremity Trauma

A 45-year-old male presents with a unilateral proximal femoral varus deformity following a childhood injury. His contralateral limb is perfectly normal. The Malalignment Test confirms significant Mechanical Axis Deviation (MAD), but the tibial joint angles (MPTA, LDTA) and the distal femoral joint orientation (mLDFA) are all within normal limits. The surgeon plans a mechanical axis correction. Based on the provided image and the Paley method for unilateral proximal femoral deformities, what is the next critical step in planning the Distal Mechanical Axis (DMA)?

. Draw the DMA as a direct proximal extension of the proximal tibial mechanical axis.
. Draw the DMA from the center of the knee joint extending proximally at an angle derived from the contralateral mLDFA.
. Draw the DMA from the center of the femoral head to the center of the ankle joint.
. Draw the DMA as the mid-diaphyseal line of the distal femoral segment.
. Measure the Anatomic Lateral Distal Femoral Angle (aLDFA) to determine the DMA.

Correct Answer & Explanation

. Draw the DMA from the center of the knee joint extending proximally at an angle derived from the contralateral mLDFA.

Explanation

Correct Answer: BAs per the 'Scenario One: Unilateral Proximal Femoral Deformity' section, when the contralateral limb is perfectly normal and the distal femoral joint orientation (mLDFA) is unaffected by the proximal deformity, the surgeon can use the healthy contralateral limb as a perfect patient-specific template. The Distal Mechanical Axis (DMA) is then drawn as a line starting from the center of the knee joint and extending proximally at an angle (the target angle) that matches the normal contralateral mLDFA (e.g., 87° relative to the distal femoral joint line). This ensures the distal joint orientation is restored to normal.Option A is incorrectbecause this approach is used in 'Advanced Scenario Two: Bilateral and Multiapical Deformities' when the contralateral limb is also deformed, and the MPTA and JLCA are normal. In this unilateral case, the contralateral mLDFA is the direct template.Option C is incorrectbecause drawing a line from the center of the femoral head to the center of the ankle joint defines the overall mechanical axis of the limb (Mikulicz line), which is used for the Malalignment Test, not specifically for planning the DMA in a proximal deformity.Option D is incorrectbecause the mid-diaphyseal line defines the anatomic axis, not the mechanical axis. While the distal segment is straight, the DMA is a mechanical axis, which is joint-referenced.Option E is incorrectbecause the aLDFA is an anatomic angle, primarily used for planning with intramedullary nails. For mechanical axis planning, the mLDFA is the relevant angle.

Question 295

Topic: Lower Extremity Trauma

A 28-year-old female presents with a unilateral proximal femoral valgus deformity. Her contralateral femur is anatomically normal. The surgeon plans an anatomic axis correction for a subtrochanteric osteotomy, intending to use an intramedullary nail. The image provided illustrates the initial planning steps. Given that the contralateral MPFA is 84°, what is the next logical step in determining the correct anatomic axis of the proximal segment on the deformed side?

. Measure the Mechanical Lateral Distal Femoral Angle (mLDFA) to confirm distal alignment.
. Draw an ideal anatomic axis line from the piriformis fossa extending distally at 84° relative to the proximal joint line.
. Extend the mid-diaphyseal anatomic axis line proximally until it intersects the femoral head.
. Calculate the Anatomic-Mechanical Angle (AMA) to convert to a mechanical axis plan.
. Identify the CORA by intersecting the proximal and distal mechanical axes.

Correct Answer & Explanation

. Draw an ideal anatomic axis line from the piriformis fossa extending distally at 84° relative to the proximal joint line.

Explanation

Correct Answer: BAs described in 'Scenario Three: Anatomic Planning with a Normal Contralateral Femur,' after identifying the mid-diaphyseal line of the distal segment and confirming a normal aLDFA, the next step is to determine the correct anatomic axis of the proximal segment. Since the contralateral femur is normal, the surgeon uses the normal contralateral MPFA (given as 84°) as a template. An ideal anatomic axis line is then drawn on the deformed side, starting from the piriformis fossa (the ideal entry point for an IM nail) and extending distally at this template angle (84°) relative to the proximal joint line. This line represents the desired post-correction proximal anatomic axis.Option A is incorrectbecause the mLDFA is a mechanical angle, and this scenario specifically involves anatomic axis planning. The aLDFA would be relevant for distal anatomic alignment, which is already assumed to be normal in the distal segment.Option C is incorrectbecause simply extending the mid-diaphyseal line proximally would not account for the proximal deformity and would not use the joint-referenced template from the contralateral side.Option D is incorrectbecause the goal is anatomic axis planning for an IM nail, not converting to a mechanical axis plan. The AMA is used to relate the two axes, but not for this specific step of defining the proximal anatomic axis using a contralateral template.Option E is incorrectbecause this step is about defining the proximal anatomic axis. Identifying the CORA is the subsequent step, where the newly drawn proximal joint-referenced anatomic axis intersects the distal mid-diaphyseal anatomic axis.

Question 296

Topic: Lower Extremity Trauma

A 32-year-old female presents with severe genu varum. Standing full-length radiographs reveal a Mechanical Axis Deviation (MAD) of 45 mm medially. Her mechanical lateral distal femoral angle (mLDFA) is 102 degrees, and her medial proximal tibial angle (MPTA) is 87 degrees. Where is the primary source of her deformity?

. Proximal tibia
. Distal femur
. Knee joint (ligamentous laxity)
. Distal tibia
. Proximal femur

Correct Answer & Explanation

. Distal femur

Explanation

The normal mLDFA is approximately 87 degrees (range 85-90). An mLDFA of 102 degrees indicates a significant distal femoral varus deformity. The MPTA of 87 degrees is within the normal range, ruling out a tibial source.

Question 297

Topic: Lower Extremity Trauma

A 55-year-old man with medial compartment knee osteoarthritis and a varus deformity undergoes full-length standing radiographs. His Joint Line Convergence Angle (JLCA) is measured at 6 degrees, opening laterally. What does an abnormally high JLCA typically indicate in this setting?

. A pure diaphyseal bowing deformity of the tibia
. A primary valgus deformity of the distal femur
. Intra-articular deformity, such as cartilage loss or lateral ligamentous laxity
. A compensatory deformity of the ankle joint
. Normal physiological alignment for an adult

Correct Answer & Explanation

. Intra-articular deformity, such as cartilage loss or lateral ligamentous laxity

Explanation

The normal JLCA is 0 to 2 degrees. A JLCA greater than 2 degrees indicates an intra-articular contribution to the deformity, commonly due to asymmetric cartilage loss (e.g., medial compartment narrowing) or lateral ligamentous laxity.

Question 298

Topic: Lower Extremity Trauma

During radiographic assessment of the sagittal plane of the tibia, you measure the Posterior Proximal Tibial Angle (PPTA). What is the normal value for the PPTA, reflecting the natural posterior slope of the tibial plateau?

. 90 degrees
. 87 degrees
. 81 degrees
. 75 degrees
. 95 degrees

Correct Answer & Explanation

. 81 degrees

Explanation

The normal Posterior Proximal Tibial Angle (PPTA) is approximately 81 degrees (range 77-84 degrees). This represents the normal 9-degree posterior slope of the proximal tibial articular surface.

Question 299

Topic: Lower Extremity Trauma

During preoperative planning for a distal femoral deformity, the surgeon measures the mechanical lateral distal femoral angle (mLDFA). What is the accepted normal range for the mLDFA in a healthy adult?

. 75 to 80 degrees
. 81 to 84 degrees
. 85 to 90 degrees
. 91 to 95 degrees
. 96 to 100 degrees

Correct Answer & Explanation

. 85 to 90 degrees

Explanation

The normal mechanical lateral distal femoral angle (mLDFA) ranges from 85 to 90 degrees, with an average of 88 degrees. Deviations from this range indicate a structural deformity in the frontal plane of the distal femur.

Question 300

Topic: Lower Extremity Trauma

A surgeon utilizes a 'Lengthening Over a Nail' (LON) technique for a 24-year-old male with a 6 cm femoral shortening. What is the primary biological or clinical advantage of this hybrid technique over classic Ilizarov lengthening?

. It eliminates the risk of deep intramedullary infection.
. It dramatically shortens the latency phase required before distraction.
. It allows for earlier removal of the external fixator by using the nail to support the consolidation phase.
. It inherently prevents any equinus or knee flexion contractures.
. It increases the rate of distraction to 3 mm per day safely.

Correct Answer & Explanation

. It allows for earlier removal of the external fixator by using the nail to support the consolidation phase.

Explanation

The primary advantage of Lengthening Over a Nail (LON) is that the intramedullary nail stabilizes the bone during the consolidation phase. This allows the external fixator to be removed much earlier, significantly improving patient comfort.

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