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 2801
Topic: 2. Trauma
A 28-year-old soccer player undergoes an isolated lateral compartment fasciotomy for CECS. Postoperatively, he reports decreased sensation over the dorsum of his foot, but sensation in the first dorsal webspace remains intact. Which structure was most likely injured during the procedure?
Correct Answer & Explanation
. Superficial peroneal nerve
Explanation
The superficial peroneal nerve provides sensation to the dorsum of the foot and is at high risk during lateral compartment fasciotomy as it exits the fascia approximately 10-12 cm proximal to the lateral malleolus.
Question 2802
Topic: 2. Trauma
A 25-year-old male presents with recurrent anterior compartment CECS one year after undergoing a single-incision anterior/lateral fasciotomy. What is the most common anatomic reason for recurrent anterior compartment syndrome following operative release?
Correct Answer & Explanation
. Inadequate release of the distal fascia near the extensor retinaculum
Explanation
The most common cause of recurrence in anterior compartment CECS is incomplete fasciotomy, specifically failing to adequately release the distal fascial envelope near the proximal extensor retinaculum.
Question 2803
Topic: Lower Extremity Trauma
A 55-year-old male presents with significant knee recurvatum. Preoperative planning reveals a Mechanical Posterior Proximal Tibial Angle (mPPTA) of 88° and a normal Mechanical Posterior Distal Femoral Angle (mPDFA) of 82°. The surgeon, aiming for a 'straight leg,' performs a distal femoral flexion osteotomy to correct the clinical hyperextension.
Correct Answer & Explanation
. Iatrogenic posterior knee subluxation
Explanation
Correct Answer: BThe case content emphasizes the critical axiom: 'You must correct the deformity in the bone where it actually exists.' The patient has a reversed posterior tibial slope (mPPTA > 84°), indicating that the tibia is the true source of the recurvatum. The mPDFA is normal, meaning the femur is not deformed. By performing a flexion osteotomy of the distal femur (the wrong bone), the femoral condyles are now pointing abnormally downward onto a tibial plateau that is still sloped backward. The text explicitly states: 'With every single step, weight-bearing forces will cause the femur to literally slide off the back of the tibia, creating a devastatingiatrogenic posterior knee subluxation.'Option A is incorrect; anterior subluxation would occur if femoral recurvatum were corrected in the tibia. Option C (patella baja) is typically associated with proximal tibial osteotomies performed incorrectly relative to the tibial tuberosity, not distal femoral osteotomies. Options D and E are general surgical complications but not the specific biomechanical catastrophe predicted by violating Paley's fundamental rule in this scenario.
Question 2804
Topic: 2. Trauma
A 40-year-old patient with a history of distal femoral fracture malunion presents with 15 degrees of knee recurvatum. Radiographic analysis reveals a Mechanical Posterior Distal Femoral Angle (mPDFA) of 98° (normal 80-85°) and a normal Mechanical Posterior Proximal Tibial Angle (mPPTA) of 81° (normal 77-84°). The Center of Rotation of Angulation (CORA) is identified in the distal femoral metaphysis.
Correct Answer & Explanation
. At the CORA within the distal femoral metaphysis, with simple angular correction
Explanation
Correct Answer: CThe case content defines the CORA as 'the apex of the deformity—the precise mathematical point where the proximal and distal anatomical (or mechanical) axes of a deformed bone intersect.' It further states that 'Identifying the CORA is not a mere academic exercise; it is the single most important step in preoperative planning. The CORA dictates the ideal location for your surgical osteotomy.' According to Paley's Osteotomy Rule 1: 'If the osteotomy is performed exactlyat the CORA, simple angular correction will perfectly realign the proximal and distal bone axes without creating any unwanted translation.' In this patient, the deformity is clearly femoral (mPDFA = 98°), and the CORA is located in the distal femoral metaphysis. Therefore, performing the osteotomy at this CORA allows for a precise angular correction without inducing secondary translation.Option A is incorrect; a joint-line CORA indicates a soft tissue deformity, not a bony one, and would necessitate translation. Options B, D, and E are incorrect because the deformity is in the distal femur, and performing the osteotomy in the tibia or away from the CORA in the femur would either violate the principle of correcting the deformity where it lives or necessitate additional translation (Rule 2), which is not the ideal scenario when the CORA is accessible.
Question 2805
Topic: Lower Extremity Trauma
A patient with a severe knee deformity undergoes full-length weight-bearing lateral radiography. A plumb line dropped from the center of the femoral head passes significantly posterior to the center of the knee joint.
Correct Answer & Explanation
. Knee hyperextension (recurvatum)
Explanation
Correct Answer: BThe case content describes the normal sagittal mechanical axis: 'In a normal, healthy standing posture... a plumb line dropped from the center of the femoral head should pass...Anterior to the center of the knee joint... This specific anterior positioning creates a natural extension moment at the knee.' It then states: 'Conversely, excessive posterior deviation, where the mechanical axis falls behind the center of the knee, signifies a hyperextension deformity (recurvatum).' Therefore, a plumb line passing significantly posterior to the knee joint indicates recurvatum.Option A is incorrect; excessive anterior deviation of the distal femur or proximal tibia indicates a flexion deformity (procurvatum). Option C is incorrect as the axis should pass anterior to the knee. Options D and E describe coronal plane deformities, which are not assessed by the sagittal mechanical axis.
Question 2806
Topic: Lower Extremity Trauma
A 28-year-old patient presents with 18 degrees of clinical knee hyperextension. Full-length lateral radiographs reveal a Mechanical Posterior Distal Femoral Angle (mPDFA) of 82° (normal 80-85°) and a Mechanical Posterior Proximal Tibial Angle (mPPTA) of 89° (normal 77-84°).
Correct Answer & Explanation
. Tibial recurvatum
Explanation
Correct Answer: BThe case content provides a clear diagnostic algorithm: 'If the mPDFA is > 85°, the source of the deformity isfemoral. If the mPPTA is > 84°, the source of the deformity istibial.' In this patient, the mPDFA of 82° is within the normal range, ruling out femoral osseous deformity. However, the mPPTA of 89° is significantly greater than the normal upper limit of 84°, indicating a flattened or reversed posterior slope of the tibial plateau. This directly points to tibial recurvatum as the primary source of the deformity.Option A is incorrect because the mPDFA is normal. Option C is incorrect because the mPPTA is abnormal, indicating an osseous deformity. Option D is incorrect because only the tibia shows an osseous deformity. Option E is a potential etiology but the question asks for the primary source of the deformity based on the given radiographic measurements, which clearly point to a structural tibial issue.
Question 2807
Topic: Lower Extremity Trauma
A 48-year-old male presents with a sagittal plane knee deformity. To accurately quantify the bony architecture, a true lateral radiograph is obtained. Which of the following statements correctly defines the Posterior Distal Femoral Angle (PDFA) and its normal range, according to Paley's principles?
Correct Answer & Explanation
. The angle formed between the anatomic axis of the femur and the joint line of the distal femoral condyles, normally 83° ± 4°.
Explanation
Correct Answer: CThe case defines the Posterior Distal Femoral Angle (PDFA) as 'the angle formed between the anatomic axis of the femur and the joint line of the distal femoral condyles.' It also states the normal value range for PDFA is '83° ± 4°'.Option A describes the PPTA and its normal range is incorrect for PDFA. Option B correctly defines PDFA but provides the normal range for PPTA. Option D incorrectly refers to the mechanical axis instead of the anatomic axis. Option E describes the PPTA and its normal range, not the PDFA.
Question 2808
Topic: Lower Extremity Trauma
According to Paley's principles, the Center of Rotation of Angulation (CORA) is a critical concept for precise deformity correction. For a patient presenting with an isolated femoral procurvatum deformity, where would the CORA typically be located?
Correct Answer & Explanation
. In the distal femur, proximal to the joint line.
Explanation
Correct Answer: BThe case states, 'A decreased PDFA signifies that the distal femoral joint surface is pathologically tilted anteriorly (into extension) relative to the femoral shaft. This creates afemoral procurvatumdeformity. The CORA for this specific deformity is located in the distal femur.' While the exact point within the distal femur can vary, it is generally proximal to the joint line, where the angulation occurs.Option A is incorrect as it describes the location for a tibial deformity. Option C is incorrect; a CORA at the joint line would imply a joint-level deformity, not a specific bony angulation within the femur. Option D is incorrect; mid-diaphyseal CORAs are typically associated with diaphyseal bowing, not juxta-articular procurvatum. Option E is unrelated to the CORA of a femoral procurvatum.
Question 2809
Topic: 2. Trauma
A 28-year-old patient presents with a long-standing history of a crouched gait, difficulty with prolonged standing, and recurrent anterior knee pain. Clinical examination reveals a significant fixed flexion deformity of the knee. The patient denies any acute trauma. Based on the case, which of the following is the MOST accurate initial diagnostic approach for this patient's FFD?
Correct Answer & Explanation
. Recognize FFD as a clinical sign and meticulously quantify bony and soft tissue components using a true lateral radiograph and Paley's angles.
Explanation
Correct Answer: CThe case explicitly states, 'The critical first step in preoperative planning is a paradigm shift:an FFD is a clinical sign, not a final diagnosis.It is a symptom that can arise from three distinct anatomic sources, often presenting in complex combinations: bony deformity of the distal femur, bony deformity of the proximal tibia, and soft tissue contracture.' It further emphasizes the need to 'meticulously quantify the bony architecture using standardized joint orientation angles on a high-quality, true lateral radiograph.'Options A, D, and E are incorrect because they assume a single etiology for FFD and jump to specific treatments or less comprehensive diagnostic steps without first differentiating the underlying components. Option B is incorrect because while patellofemoral issues are a consequence, a CT scan is not the initial or primary tool for differentiating the bony and soft tissue components of FFD in the sagittal plane; a true lateral radiograph is paramount for Paley's angle measurements.
Question 2810
Topic: 2. Trauma
A patient sustained a distal femur fracture managed non-operatively 10 years ago. A standing full-length lateral radiograph reveals a Mechanical Posterior Distal Femoral Angle (mPDFA) of 70°. What is the precise nature of this sagittal plane deformity?
Correct Answer & Explanation
. Distal femoral procurvatum (apex anterior)
Explanation
Normal mPDFA is approximately 83°. An mPDFA of 70° indicates that the posterior angle is decreased, meaning the distal articular surface is tilted posteriorly. This corresponds to an apex anterior bowing of the distal femur, which is clinically defined as distal femoral procurvatum.
Question 2811
Topic: 2. Trauma
During a distal femoral osteotomy to correct a sagittal plane deformity, the mechanical hinge axis is inadvertently aligned obliquely rather than perfectly perpendicular to the sagittal plane. What is the primary biomechanical consequence?
Correct Answer & Explanation
. Induction of an iatrogenic varus or valgus coronal plane deformity
Explanation
If the axis of correction (hinge) is not strictly perpendicular to the plane of the deformity, angular correction will couple out of the primary plane, unintentionally inducing a secondary angulation (varus or valgus) in the coronal plane.
Question 2812
Topic: Lower Extremity Trauma
When calculating the mPDFA for preoperative planning of a sagittal deformity, the mechanical axis of the femur in the sagittal plane must be drawn. Which two anatomic landmarks properly define this axis?
Correct Answer & Explanation
. Center of the femoral head and the center of the distal femoral joint line in the sagittal profile
Explanation
The sagittal mechanical axis of the femur is defined by a line connecting the center of rotation of the femoral head to the center of the distal femoral joint space on a true lateral radiograph.
Question 2813
Topic: 2. Trauma
A patient presents with a severe fixed flexion contracture of the knee (35 degrees) secondary to a malunited distal femur fracture. If acute correction via an extension closing wedge osteotomy is planned, what is the most critical limiting factor for the amount of acute correction obtainable?
Correct Answer & Explanation
. Traction injury to the sciatic/peroneal nerves
Explanation
Acute correction of severe knee flexion contractures places immediate, high stretch on the posterior neurovascular structures. The sciatic nerve, and particularly its common peroneal branch, is highly sensitive to traction injury, often limiting acute correction.
Question 2814
Topic: Lower Extremity Trauma
When analyzing the Joint Line Convergence Angle (JLCA) in the sagittal plane of a normal knee, how do the distal femoral and proximal tibial joint lines relate to one another?
Correct Answer & Explanation
. They are roughly parallel (angle close to 0 degrees)
Explanation
In the normal knee, the sagittal joint lines of the distal femur and proximal tibia are roughly parallel (JLCA near 0 degrees). Significant deviation indicates either cartilage loss, ligamentous laxity, or intra-articular deformity.
Question 2815
Topic: Lower Extremity Trauma
In applying Paley's Rule 1 to correct a sagittal deformity of the distal femur, which of the following statements strictly characterizes the surgical technique?
Correct Answer & Explanation
. The osteotomy and the hinge are both located exactly at the CORA
Explanation
Paley's Rule 1 dictates that both the osteotomy cut and the mechanical axis of rotation (hinge) are located at the Center of Rotation of Angulation (CORA), resulting in pure angular correction without translation.
Question 2816
Topic: Lower Extremity Trauma
A 45-year-old patient presents with a clinically apparent knee procurvatum (flexion deformity). Full-length sagittal radiographs reveal a normal mPPTA of 82° and an abnormal femoral parameter. Which of the following mPDFA values confirms an apex anterior (procurvatum) deformity of the distal femur?
Correct Answer & Explanation
. 72°
Explanation
An mPDFA significantly less than 80° indicates an apex anterior bow (procurvatum) of the distal femur, leading to a fixed flexion deformity. An mPDFA greater than 85° indicates recurvatum.
Question 2817
Topic: 2. Trauma
A patient with a chronic distal femoral fracture malunion develops a fixed bony recurvatum deformity (mPDFA = 96°). To maintain a plantigrade foot and an upright posture over time, what compensatory bony or positional change is most likely to develop in the ipsilateral tibia?
Correct Answer & Explanation
. Increased mPPTA (Procurvatum)
Explanation
To compensate for a femoral extension deformity (recurvatum), the tibia will often develop a compensatory flexion deformity (procurvatum) to keep the leg relatively straight for weight-bearing. Procurvatum of the tibia increases the mPPTA.
Question 2818
Topic: Lower Extremity Trauma
A patient presents with a severe knee recurvatum deformity. Radiographs reveal a mechanical posterior distal femoral angle (mPDFA) of 96 degrees and a mechanical posterior proximal tibial angle (mPPTA) of 81 degrees. According to Paley's principles, where is the primary site of the bony deformity?
Correct Answer & Explanation
. Distal femur with an apex posterior deformity
Explanation
The normal mPDFA is 83 degrees. An increased mPDFA (96 degrees) indicates the distal articular surface is extended relative to the shaft, representing a distal femoral apex posterior deformity (recurvatum).
Question 2819
Topic: Lower Extremity Trauma
When analyzing the sagittal plane alignment of the lower extremity using Paley's principles, where should the normal mechanical axis (plumb line from the center of the femoral head) pass relative to the knee joint?
Correct Answer & Explanation
. Anterior to the center of the knee joint
Explanation
In the sagittal plane, the normal mechanical axis (plumb line) drops from the center of the femoral head and passes slightly anterior to the center of the knee joint, terminating at the center of the ankle.
Question 2820
Topic: 2. Trauma
A 35-year-old female presents with clinical knee recurvatum. Her standing full-length lateral radiograph shows a normal mPDFA (82 degrees) and normal mPPTA (81 degrees). However, there is a prominent Sagittal Joint Line Convergence Angle (sJLCA). What is the primary etiology of her deformity?
Correct Answer & Explanation
. Soft tissue/capsular hyperlaxity
Explanation
A normal mPDFA and mPPTA indicate the bones themselves do not have a sagittal deformity. An increased sJLCA indicates the joint space is opening asymmetrically, pointing to soft tissue laxity or capsular hyperextension as the cause.
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