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Lower Extremity Trauma MCQs

Practice Set 17 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 321

Topic: Lower Extremity Trauma

A 32-year-old professional athlete is undergoing pre-operative planning for a limb alignment procedure. The surgeon emphasizes the importance of understanding the normal values for joint orientation angles. According to Paley's principles, what are the normal values for the Mechanical Lateral Distal Femoral Angle (mLDFA) and the Medial Proximal Tibial Angle (MPTA), and what do they primarily define?

. mLDFA: 80° (defines distal femur); MPTA: 90° (defines proximal tibia).
. mLDFA: 87° (defines distal femur); MPTA: 87° (defines proximal tibia).
. mLDFA: 90° (defines proximal femur); MPTA: 87° (defines distal tibia).
. mLDFA: 87° (defines proximal tibia); MPTA: 87° (defines distal femur).
. mLDFA: 90° (defines distal femur); MPTA: 80° (defines proximal tibia).

Correct Answer & Explanation

. mLDFA: 87° (defines distal femur); MPTA: 87° (defines proximal tibia).

Explanation

Correct Answer: BThe text explicitly states the normal values for these critical frontal plane joint orientation angles: 'Mechanical Lateral Distal Femoral Angle (mLDFA) | 87° | 85° - 90° | Defines the alignment of the distal femur' and 'Medial Proximal Tibial Angle (MPTA) | 87° | 85° - 90° | Defines the alignment of the proximal tibia.' These angles are crucial for pinpointing the source of a deformity.Options A, C, D, and E are incorrect as they either misstate the normal values, incorrectly assign the anatomical region defined by the angle, or both. The mLDFA defines the distal femur, and the MPTA defines the proximal tibia.

Question 322

Topic: Lower Extremity Trauma

A 60-year-old male presents with progressive medial compartment osteoarthritis and a clinical varus deformity of his right lower extremity. A full-length standing radiograph, similar to the one shown, confirms a positive Mechanical Axis Deviation (MAD) of +20mm. Further analysis reveals a normal Mechanical Lateral Distal Femoral Angle (mLDFA) of 87°.

Based on this information and Paley's principles, which joint orientation angle is most likely abnormal and contributing to the patient's varus alignment?

. Lateral Distal Tibial Angle (LDTA)
. Medial Proximal Tibial Angle (MPTA)
. Anatomical Lateral Distal Femoral Angle (aLDFA)
. Posterior Proximal Tibial Angle (PPTA)
. Tibial Torsion Angle

Correct Answer & Explanation

. Medial Proximal Tibial Angle (MPTA)

Explanation

Correct Answer: BThe patient has a varus deformity (positive MAD). The text states that the mLDFA defines the alignment of the distal femur, and an abnormal value points to a femoral source. Since the mLDFA is normal (87°), the deformity is not originating from the distal femur. The MPTA (Medial Proximal Tibial Angle) defines the alignment of the proximal tibia and is described as 'the absolute key' for proximal tibial alignment. A varus deformity originating from the proximal tibia would manifest as a decreased MPTA (normal 87°). Therefore, with a normal mLDFA and a varus deformity, the MPTA is the most likely abnormal angle contributing to the varus alignment.Option A (LDTA) is primarily associated with distal tibial alignment and typically contributes to valgus deformities if abnormal (increased LDTA), or a distal varus if decreased, but less commonly the primary cause of a global varus when the proximal tibia is the more common site for varus. The question implies a single primary source given the normal mLDFA.Option C (aLDFA) is an anatomical angle, not a mechanical angle, and while related to femoral alignment, the mLDFA is the mechanical angle used in Paley's frontal plane analysis.Option D (PPTA) is a sagittal plane angle, not a frontal plane angle, and would not directly cause a frontal plane varus deformity.Option E (Tibial Torsion Angle) is a rotational measurement, not a frontal plane angular deformity.

Question 323

Topic: Lower Extremity Trauma

A 30-year-old female presents with chronic lateral knee pain and a noticeable 'knock-knee' appearance. A full-length standing anteroposterior radiograph, similar to the one provided, confirms a negative Mechanical Axis Deviation (MAD) of -15mm. Further analysis reveals a normal Medial Proximal Tibial Angle (MPTA) of 87° and a normal Mechanical Lateral Distal Femoral Angle (mLDFA) of 87°.

Given these findings, which of the following is the most likely anatomical source of the patient's valgus deformity?

. Proximal femur
. Distal femur
. Proximal tibia
. Distal tibia
. Ankle joint

Correct Answer & Explanation

. Distal tibia

Explanation

Correct Answer: DThe patient has a valgus deformity (negative MAD). The text states that mLDFA defines distal femoral alignment and MPTA defines proximal tibial alignment. Both mLDFA (87°) and MPTA (87°) are within the normal range (85°-90°). This rules out the distal femur and proximal tibia as the primary sources of the frontal plane deformity. Since the deformity is in the lower extremity and not originating from the femur or proximal tibia, the most likely remaining anatomical source for a frontal plane deformity, especially a valgus, is the distal tibia. An abnormal Lateral Distal Tibial Angle (LDTA), which is typically 89° (range 87°-92°), would indicate a distal tibial deformity. While the text did not explicitly list LDTA's normal value in the table, it states 'four specific angles are paramount' for tibial deformity correction, and LDTA is a fundamental frontal plane angle for the distal tibia in Paley's system.Option A (Proximal femur) is not directly assessed by mLDFA or MPTA in the frontal plane, but if the deformity was proximal femur, it would typically affect the overall mechanical axis and potentially mLDFA indirectly. However, with normal mLDFA and MPTA, it's less likely the primary source.Option B (Distal femur) is ruled out by the normal mLDFA.Option C (Proximal tibia) is ruled out by the normal MPTA.Option E (Ankle joint) deformities are typically assessed by different angles (e.g., Talar Tilt) and are less common as the sole cause of a significant global valgus MAD without an underlying long bone deformity.

Question 324

Topic: Lower Extremity Trauma

A 40-year-old patient presents with a significant Mechanical Axis Deviation (MAD) of +18mm, indicating a varus deformity. Upon detailed radiographic analysis, the Mechanical Lateral Distal Femoral Angle (mLDFA) is measured at 87°. Based on Paley's principles, what is the most accurate conclusion regarding the primary source of this patient's frontal plane deformity?

. The deformity is solely located in the distal femur.
. The deformity is solely located in the proximal femur.
. The deformity is primarily located in the tibia.
. The deformity is a combined femoral and tibial deformity.
. The MAD measurement is likely erroneous, as a normal mLDFA should result in a normal MAD.

Correct Answer & Explanation

. The deformity is primarily located in the tibia.

Explanation

Correct Answer: CThe text states that the mLDFA 'Defines the alignment of the distal femur. An abnormal value points to a femoral source for the overall limb malalignment.' Since the mLDFA is measured at 87°, which is within the normal range (85°-90°), it indicates that the distal femur is normally aligned in the frontal plane. With an abnormal MAD (indicating a deformity) and a normal mLDFA, the primary source of the frontal plane deformity must therefore be located in the tibia (either proximal or distal).Option A is incorrect because a normal mLDFA rules out the distal femur as the sole or primary source.Option B is incorrect because while a proximal femoral deformity could exist, the mLDFA specifically assesses the distal femur, and the overall conclusion points away from the femur as the primary source of thefrontal planedeformity when mLDFA is normal.Option D is incorrect because while combined deformities are possible, with a normal mLDFA, the femoral contribution to the frontal plane malalignment is ruled out, making the tibia the primary source.Option E is incorrect; a normal mLDFA does not guarantee a normal MAD if there is a deformity elsewhere in the limb, such as the tibia. The MAD is a global measurement, while mLDFA is a segment-specific measurement.

Question 325

Topic: Lower Extremity Trauma

A 28-year-old patient presents with a valgus deformity and a negative Mechanical Axis Deviation (MAD) of -12mm. Radiographic analysis reveals a Medial Proximal Tibial Angle (MPTA) of 87° and a Mechanical Lateral Distal Femoral Angle (mLDFA) of 80°. The distal tibia is also being evaluated.

Based on these findings and Paley's principles, what is the most appropriate conclusion regarding the primary source of this patient's frontal plane deformity?

. The deformity is solely located in the proximal tibia.
. The deformity is solely located in the distal tibia.
. The deformity is primarily located in the distal femur.
. The deformity is a combined proximal tibial and distal femoral deformity.
. The deformity is primarily located in the ankle joint.

Correct Answer & Explanation

. The deformity is primarily located in the distal femur.

Explanation

Correct Answer: CThe patient has a valgus deformity (negative MAD). The MPTA is 87°, which is within the normal range (85°-90°), ruling out the proximal tibia as the primary source of the frontal plane deformity. However, the mLDFA is 80°, which is outside the normal range of 85°-90°. The text states, 'An abnormal value [mLDFA] points to a femoral source for the overall limb malalignment.' An mLDFA of 80° (less than 87°) indicates a valgus deformity originating from the distal femur. Therefore, the primary source of this patient's frontal plane deformity is the distal femur.Option A is incorrect because the MPTA is normal, ruling out the proximal tibia as the primary source.Option B is incorrect because while the distal tibia could contribute, the mLDFA is clearly abnormal and points to the distal femur as the primary source. The image of the distal tibia is provided to prompt consideration of this area, but the given angle measurements are key.Option D is incorrect because while a combined deformity is possible, the MPTA is normal, so it's not a combined proximal tibial and distal femoral deformity. It is primarily a distal femoral deformity.Option E is incorrect; while the ankle joint can have deformities, the abnormal mLDFA clearly identifies the distal femur as the primary source of the overall limb malalignment.

Question 326

Topic: Lower Extremity Trauma
A surgeon is planning an intramedullary femoral lengthening using a PRECICE nail for a patient with femoral shortening. During preoperative templating, the surgeon must account for the natural relationship between the femoral anatomic and mechanical axes. What is the normal Anatomic-Mechanical Angle (AMA) of the femur, and why is it clinically vital to consider this angle during intramedullary nailing procedures?
. 0 degrees; it ensures the nail follows the mechanical axis directly.
. Approximately 7 degrees; failing to account for it will result in a malaligned limb.
. Approximately 15 degrees; it helps determine the entry point for the nail.
. 88 degrees; it dictates the distal locking screw trajectory.
. 90 degrees; it prevents rotational malalignment.

Correct Answer & Explanation

. Approximately 7 degrees; failing to account for it will result in a malaligned limb.

Explanation

The natural, complex shape of the femur causes its anatomic and mechanical axes to diverge, forming the Anatomic-Mechanical Angle (AMA). In a normal femur, this angle is approximately 7 degrees (with a physiological range of 5 to 9 degrees). This relationship is clinically vital, especially during intramedullary procedures, because the anatomic axis (which dictates the nail's physical path) is used as a surrogate for correcting the mechanical axis. Failing to account for the 7-degree AMA will result in a malaligned limb.

Question 327

Topic: Lower Extremity Trauma

A surgeon is planning a corrective osteotomy for a patient with a post-traumatic angular deformity of the tibia. After drawing the proximal and distal mechanical axes, they identify their intersection point. What is the significance of the point where the proximal and distal axis lines of a deformed bone segment intersect, and why is it crucial for surgical planning?

. It defines the anatomic-mechanical angle, guiding intramedullary nail placement.
. It is the Mechanical Axis Deviation (MAD), indicating the overall limb malalignment.
. It represents the Center of Rotation of Angulation (CORA), the precise point around which an osteotomy must be performed to achieve realignment without translation.
. It is the Joint Line Convergence Angle, indicating intra-articular pathology.
. It identifies the exact location for hardware placement, such as a plate.

Correct Answer & Explanation

. It represents the Center of Rotation of Angulation (CORA), the precise point around which an osteotomy must be performed to achieve realignment without translation.

Explanation

Correct Answer: CThe case defines the Center of Rotation of Angulation (CORA) as the precise point in two-dimensional space around which a deformed bone must be rotated to achieve perfect realignment without creating a secondary, unwanted translational deformity. It is found by drawing the axis lines of the normal proximal and distal bone segments (proximal mechanical/anatomic axis and distal mechanical/anatomic axis) and identifying their intersection. An osteotomy performed exactly at the CORA will perfectly realign the two axes, restoring the bone to its natural geometry without translation.Option A is incorrect; the AMA is a specific angle between the anatomic and mechanical axes of the femur. Option B is incorrect; MAD quantifies overall limb malalignment, not the apex of a specific bone deformity. Option D is incorrect; JLCA assesses intra-articular pathology. Option E is too general; while the CORA guides osteotomy placement, which in turn influences hardware placement, its primary significance is as the geometric center of rotation for correction, not just a hardware location.

Question 328

Topic: Lower Extremity Trauma

A resident is reviewing a long-leg radiograph and wants to quickly assess if the knee is properly rotated for a true AP view. According to Paley's principles, which radiographic sign is a reliable indicator that the knee is in a true anteroposterior (AP) view, minimizing rotational error?

. The patella is perfectly centered over the femoral trochlea.
. The fibular head is approximately one-third overlapped by the lateral tibial plateau.
. The joint line convergence angle (JLCA) is less than 2 degrees.
. The mechanical axis passes 8 ± 7 mm medial to the knee center.
. The femoral condyles are perfectly superimposed.

Correct Answer & Explanation

. The fibular head is approximately one-third overlapped by the lateral tibial plateau.

Explanation

Correct Answer: BThe case provides 'Surgical Pearl 2: Verify the Film,' which states: 'Before analyzing any angles, look at the fibular head. In a true AP view of the knee, the fibular head should be approximately one-third overlapped by the lateral tibial plateau. If it is completely hidden or completely exposed, the knee is rotated.' This is a quick and reliable indicator of proper knee rotation in the frontal plane.Option A is a good clinical sign but not explicitly mentioned as the primary radiographic sign for rotation verification in the text. Option C relates to intra-articular pathology and stability, not rotation. Option D describes normal overall limb alignment, not knee rotation. Option E is a sign of proper rotation, but the text specifically highlights the fibular head overlap as a key 'surgical pearl' for verification.

Question 329

Topic: Lower Extremity Trauma

A 35-year-old patient presents for evaluation of a complex lower limb deformity. A full-length standing AP radiograph is obtained. The surgeon measures the Mechanical Lateral Distal Femoral Angle (mLDFA) as 82° and the Medial Proximal Tibial Angle (MPTA) as 84°. Based on these measurements and Paley's normative data, which of the following statements accurately describes the patient's deformity?

. The patient has a varus deformity of the distal femur and a valgus deformity of the proximal tibia.
. The patient has a valgus deformity of the distal femur and a varus deformity of the proximal tibia.
. The patient has normal alignment of the distal femur and a varus deformity of the proximal tibia.
. The patient has a varus deformity of the distal femur and normal alignment of the proximal tibia.
. The patient has a valgus deformity of the distal femur and a valgus deformity of the proximal tibia.

Correct Answer & Explanation

. The patient has a valgus deformity of the distal femur and a varus deformity of the proximal tibia.

Explanation

Correct Answer: BAccording to Paley's principles, the normal range for the mLDFA is 85° to 90° (average 87°). An mLDFA less than 85° indicates a valgus deformity of the distal femur. The patient's mLDFA of 82° falls below this range, indicating a valgus deformity of the distal femur.The normal range for the MPTA is 85° to 90° (average 87°). An MPTA less than 85° indicates a varus deformity of the proximal tibia. The patient's MPTA of 84° falls below this range, indicating a varus deformity of the proximal tibia.Therefore, the patient has a valgus deformity of the distal femur and a varus deformity of the proximal tibia. This combination is often seen in complex deformities, sometimes referred to as a 'windswept' deformity if bilateral, or a 'compensatory' deformity where one segment attempts to compensate for another.

Question 330

Topic: Lower Extremity Trauma

A 70-year-old patient presents with severe knee osteoarthritis and a significant varus deformity. A full-length standing AP radiograph is obtained. The Mechanical Lateral Distal Femoral Angle (mLDFA) is measured at 92°, and the Medial Proximal Tibial Angle (MPTA) is measured at 80°. The Mechanical Axis Deviation (MAD) is significantly medial. Based on these findings, what is the most accurate localization of the deformity?

. The deformity is solely located in the distal femur, causing a valgus alignment.
. The deformity is solely located in the proximal tibia, causing a varus alignment.
. The deformity is a combined varus deformity originating from both the distal femur and the proximal tibia.
. The deformity is a combined valgus deformity originating from both the distal femur and the proximal tibia.
. The deformity is primarily intra-articular, not amenable to extra-articular osteotomy.

Correct Answer & Explanation

. The deformity is a combined varus deformity originating from both the distal femur and the proximal tibia.

Explanation

Correct Answer: CLet's analyze the given measurements against Paley's normative data:mLDFA (Mechanical Lateral Distal Femoral Angle):Normal range is 85° to 90° (average 87°). An angle >90° indicates a varus deformity of the distal femur. The patient's mLDFA of 92° is greater than 90°, indicating a distal femoral varus.MPTA (Medial Proximal Tibial Angle):Normal range is 85° to 90° (average 87°). An angle <85° indicates a varus deformity of the proximal tibia. The patient's MPTA of 80° is less than 85°, indicating a proximal tibial varus.Since both the mLDFA and MPTA are outside their normal ranges in a manner consistent with varus (mLDFA >90° and MPTA <85°), the deformity is a combined varus deformity originating from both the distal femur and the proximal tibia. This multi-level deformity explains the significant medial MAD.Option A is incorrect as the mLDFA indicates varus, not valgus, and the tibia also has a deformity. Option B is incorrect as the femur also has a deformity. Option D is incorrect as both angles indicate varus, not valgus. Option E cannot be determined solely from these angles; while osteoarthritis is present, the angular deformities are extra-articular.

Question 331

Topic: Lower Extremity Trauma

A 45-year-old female presents with a distal femoral valgus deformity. A standing full-length radiograph shows a lateral Mechanical Axis Deviation (MAD). Her Medial Proximal Tibial Angle (MPTA) is 87 degrees, and her mechanical Lateral Distal Femoral Angle (mLDFA) is 81 degrees. Based on Paley's principles, where is the primary source of the deformity?

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

Correct Answer & Explanation

. Distal femur

Explanation

The normal mLDFA is 87 degrees (range 85-90). An mLDFA of 81 degrees indicates a valgus deformity of the distal femur. The MPTA is normal (87 degrees), ruling out a tibial origin.

Question 332

Topic: Lower Extremity Trauma

You are analyzing the sagittal profile of the femur. What is the normal anatomic Posterior Distal Femoral Angle (aPDFA), which dictates the normal sagittal orientation of the distal femur?

. 79 degrees
. 83 degrees
. 87 degrees
. 90 degrees
. 95 degrees

Correct Answer & Explanation

. 83 degrees

Explanation

The normal anatomic Posterior Distal Femoral Angle (aPDFA) is 83 degrees (range 79-87 degrees). This reflects the normal anterior bow and distal articular orientation of the femur in the sagittal plane.

Question 333

Topic: Lower Extremity Trauma

A patient presents with a severe procurvatum deformity of the distal femur. To accurately define the Center of Rotation of Angulation (CORA) in the sagittal plane, the surgeon measures the Posterior Distal Femoral Angle (PDFA). What is the normal anatomical value for the PDFA?

. 75 degrees
. 83 degrees
. 87 degrees
. 90 degrees
. 95 degrees

Correct Answer & Explanation

. 83 degrees

Explanation

The normal Posterior Distal Femoral Angle (PDFA) in the sagittal plane is 83°. Deviations from this value indicate procurvatum or recurvatum deformities of the distal femur.

Question 334

Topic: Lower Extremity Trauma

A 28-year-old patient is undergoing femur lengthening over an intramedullary nail (LON). What is the primary advantage of this technique compared to classic Ilizarov lengthening with a circular frame alone?

. Decreased total time the patient must wear the external fixator.
. Elimination of the risk of deep bone infection.
. Ability to correct severe multiplanar angular deformities simultaneously.
. Faster absolute rate of bone regenerate formation (distraction phase).
. Avoidance of the latency period prior to distraction.

Correct Answer & Explanation

. Decreased total time the patient must wear the external fixator.

Explanation

Lengthening Over a Nail (LON) allows the external fixator to be removed immediately after the distraction phase. The internal nail supports the bone during the consolidation phase, significantly reducing frame time.

Question 335

Topic: Lower Extremity Trauma

In evaluating a patient with a valgus knee, the Mechanical Axis Deviation (MAD) is lateral to the center of the knee. The mLDFA is 81° and the MPTA is 87°. Where is the primary deformity located?

. Distal femur.
. Proximal tibia.
. Knee joint line (intra-articular).
. Femoral diaphysis.
. Ankle joint.

Correct Answer & Explanation

. Distal femur.

Explanation

The MAD is lateral, indicating valgus. A decreased mLDFA (<85°) points to distal femoral valgus, while the normal MPTA confirms the proximal tibia is uninvolved.

Question 336

Topic: Lower Extremity Trauma

A 19-year-old female presents with a cosmetic "knock-knee" deformity. Radiographs reveal a Mechanical Axis Deviation (MAD) of 25 mm lateral to the knee center. Her mLDFA is 81 degrees and her MPTA is 88 degrees. Based on Paley's principles, what is the primary source of her deformity?

. Proximal tibial valgus
. Distal femoral varus
. Distal femoral valgus
. Proximal tibial varus
. Combined femoral and tibial deformities

Correct Answer & Explanation

. Distal femoral valgus

Explanation

The normal mLDFA is 87 degrees. An mLDFA of 81 degrees indicates an abnormal distal femur with a valgus deformity (angle < 87 degrees). The MPTA of 88 degrees is within normal limits.

Question 337

Topic: Lower Extremity Trauma

A 40-year-old patient presents with a valgus knee deformity. Radiographic analysis, similar to the principles shown in the diagram below, reveals a mechanical lateral distal femoral angle (mLDFA) of 95 degrees and a medial proximal tibial angle (MPTA) of 88 degrees. Based on these measurements, where is the primary apex of the deformity located?

. Proximal tibia.
. Distal femur.
. Mid-diaphysis of the femur.
. Mid-diaphysis of the tibia.
. At the ankle joint.

Correct Answer & Explanation

. Distal femur.

Explanation

Correct Answer: BThe normal range for the mechanical lateral distal femoral angle (mLDFA) is typically 85-90 degrees. A value of 95 degrees indicates that the distal femur is in valgus relative to the femoral mechanical axis (i.e., the distal femur is angled more laterally than normal). The normal range for the medial proximal tibial angle (MPTA) is also typically 85-90 degrees. An MPTA of 88 degrees is within the normal range, indicating no significant deformity originating from the proximal tibia. Therefore, the primary apex of the valgus deformity is located in the distal femur.Option A is incorrect because the MPTA is normal. Options C and D are incorrect because the mLDFA and MPTA specifically assess the angles at the knee joint, indicating deformities in the metaphyseal regions of the femur and tibia, respectively, not typically the mid-diaphysis unless there's a specific diaphyseal bend. Option E is incorrect as the ankle joint angles are not assessed by mLDFA or MPTA.

Question 338

Topic: Lower Extremity Trauma

A 35-year-old female presents with chronic lateral compartment knee pain and a valgus deformity. Radiographs show a mechanical axis passing 15 mm lateral to the center of the knee. Her mLDFA is 94 degrees, and her MPTA is 87 degrees. She is active and wishes to avoid arthroplasty. Based on the principles of frontal plane realignment, which osteotomy is most appropriate for this patient?

. Medial opening wedge high tibial osteotomy.
. Lateral closing wedge high tibial osteotomy.
. Medial closing wedge distal femoral osteotomy.
. Lateral opening wedge distal femoral osteotomy.
. Proximal fibular osteotomy.

Correct Answer & Explanation

. Medial closing wedge distal femoral osteotomy.

Explanation

Correct Answer: CThe patient has a valgus knee deformity (mechanical axis 15 mm lateral) and lateral compartment pain. The mLDFA is 94 degrees, which is greater than the normal range (85-90 degrees), indicating a valgus deformity originating from the distal femur. The MPTA is 87 degrees, which is within the normal range, ruling out a significant tibial deformity. Therefore, a distal femoral osteotomy (DFO) is indicated to correct the valgus deformity. To correct valgus, a closing wedge osteotomy on the medial side of the distal femur (or an opening wedge on the lateral side) is performed to decrease the mLDFA and shift the mechanical axis medially, offloading the lateral compartment.Option A, medial opening wedge high tibial osteotomy, is used for varus correction originating from the tibia. Option B, lateral closing wedge high tibial osteotomy, is also used for varus correction originating from the tibia. Option D, lateral opening wedge distal femoral osteotomy, would worsen a valgus deformity by increasing the mLDFA further. Option E, proximal fibular osteotomy, is a newer technique primarily for medial compartment osteoarthritis and varus knee, not for valgus deformity.

Question 339

Topic: Lower Extremity Trauma

A 55-year-old female presents with a symptomatic varus knee deformity. Preoperative full-length weight-bearing radiographs are obtained. Measurements reveal a Mechanical Lateral Distal Femoral Angle (mLDFA) of 95° (normal 88°) and a Medial Proximal Tibial Angle (MPTA) of 87° (normal 87°). The Joint Line Convergence Angle (JLCA) is 1°. Based on these findings, what is the primary anatomical location of the deformity requiring surgical correction?

. A. Proximal tibia, requiring a High Tibial Osteotomy (HTO).
. B. Distal femur, requiring a Distal Femoral Osteotomy (DFO).
. C. Proximal femur, requiring a Proximal Femoral Osteotomy.
. D. Distal tibia, requiring a Supramalleolar Osteotomy (SMOT).
. E. Both proximal tibia and distal femur, requiring a bi-level osteotomy.

Correct Answer & Explanation

. B. Distal femur, requiring a Distal Femoral Osteotomy (DFO).

Explanation

Correct Answer: BThe teaching case states that the mLDFA defines the orientation of the knee joint relative to the femur, and an abnormal mLDFA indicates a femoral deformity, requiring a Distal Femoral Osteotomy (DFO). The patient's mLDFA is 95°, which is significantly higher than the normal average of 88°. This indicates a valgus deformity originating from the distal femur, which can contribute to a varus knee if the femur is in relative valgus. Conversely, the MPTA is 87°, which is within the normal range (87°), indicating no significant deformity originating from the proximal tibia. The JLCA of 1° is also within the normal range (0-2°), suggesting no significant ligamentous laxity or asymmetric cartilage loss.Therefore, the primary anatomical location of the deformity is the distal femur, necessitating a Distal Femoral Osteotomy (DFO) to correct the abnormal mLDFA. Options A, C, D, and E are incorrect as they misidentify the primary location of the deformity based on the given angle measurements.

Question 340

Topic: Lower Extremity Trauma

A 48-year-old male presents with a complex varus deformity of the right lower extremity. Full-length weight-bearing radiographs reveal the following measurements: mLDFA = 92° (normal 88°), MPTA = 80° (normal 87°), and MAD = +20mm. The JLCA is 3°. Based on these findings and Paley's principles, what is the most appropriate initial surgical strategy?

. A. Isolated distal femoral osteotomy to correct the mLDFA.
. B. Isolated high tibial osteotomy to correct the MPTA.
. C. Bi-level osteotomy (distal femur and proximal tibia) to address both deformities.
. D. Supramalleolar osteotomy to correct the JLCA.
. E. Non-operative management with bracing due to the complex nature.

Correct Answer & Explanation

. C. Bi-level osteotomy (distal femur and proximal tibia) to address both deformities.

Explanation

Correct Answer: CThe teaching case emphasizes that 'while the MAD tells usifthere is a problem and how severe it is, the joint orientation angles tell us exactlywherethe problem is located.' In this patient, both the mLDFA and MPTA are abnormal. The mLDFA of 92° (normal 88°) indicates a femoral deformity (valgus angulation of the distal femur contributing to overall varus). The MPTA of 80° (normal 87°) indicates a tibial deformity (varus angulation of the proximal tibia). The MAD of +20mm confirms a significant varus malalignment. The JLCA of 3° (normal 0-2°) suggests some joint line convergence, possibly due to cartilage loss or ligamentous laxity, which needs to be considered but is not the primary bone deformity.Since both the femur and tibia contribute to the overall varus malalignment, an isolated osteotomy at either level would not fully correct the deformity and normalize the MAD. Therefore, a bi-level osteotomy addressing both the distal femur (DFO) and proximal tibia (HTO) is the most appropriate initial surgical strategy to restore physiological alignment. Options A and B are insufficient. Option D is incorrect as supramalleolar osteotomy addresses distal tibial deformities, and JLCA is not the primary target for osteotomy. Option E is inappropriate given the significant and symptomatic deformity.

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