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 81
Topic: Lower Extremity Trauma
An MRI is performed for a suspected Non-Ossifying Fibroma in the distal femur of a 10-year-old. The lesion shows a characteristic sclerotic rim on plain radiographs. How would this sclerotic rim typically appear on both T1-weighted and T2-weighted MRI sequences?
Correct Answer & Explanation
. Dark on both T1 and T2.
Explanation
Correct Answer: CThe sclerotic rim surrounding a Non-Ossifying Fibroma is composed of dense cortical bone. Dense cortical bone, due to its very low water content and high mineral density, typically appears dark (low signal intensity) on all MRI sequences, including both T1-weighted and T2-weighted images. This is a consistent finding for cortical bone and helps delineate the lesion from surrounding marrow and soft tissues.
Question 82
Topic: Lower Extremity Trauma
A 49-year-old female with a Lisfranc injury is being managed. The case mentions that for an undisplaced stable injury or sprain, non-operative management is an option. What does this non-operative management typically entail?
Correct Answer & Explanation
. Non-weightbearing cast for 6 weeks with regular clinical and radiological review.
Explanation
Correct Answer: BExplanation:The case clearly outlines the non-operative management for undisplaced stable injuries: "There is a role for non-operative management of an undisplaced stable injury or sprain which includes a non-weightbearing cast for 6 weeks and regular clinical and radiological review."Option A (Immediate weight-bearing in a walking boot):This is inappropriate for any Lisfranc injury, even stable ones, as it risks displacement and further damage.Option B (Non-weightbearing cast for 6 weeks with regular clinical and radiological review):This directly matches the description in the case for stable, undisplaced injuries. The non-weightbearing period allows for ligamentous healing.Option C (Physical therapy focusing on early range of motion and strengthening):Early range of motion and strengthening would be contraindicated during the initial non-weightbearing phase for a Lisfranc injury, as it could disrupt healing.Option D (Pain management with NSAIDs and activity modification only):This is insufficient for a Lisfranc injury, even a stable sprain, which requires immobilization and protection from weight-bearing.Option E (Custom orthotics and gradual return to activity):Orthotics may be used later in rehabilitation, but they are not the primary initial non-operative management for a Lisfranc injury.
Question 83
Topic: Lower Extremity Trauma
A 40-year-old male sustains an open Schatzker III tibial plateau fracture. During initial debridement, he is noted to have significant devitalized muscle and a large skin defect that cannot be closed primarily. What is the most appropriate definitive soft tissue management for this injury?
Correct Answer & Explanation
. Free tissue transfer (microvascular flap).
Explanation
An open Schatzker III tibial plateau fracture with significant devitalized muscle and a large skin defect that cannot be closed primarily requires robust soft tissue coverage, especially when bone, hardware, or vital structures are exposed. In cases of large defects or significant muscle loss, free tissue transfer (microvascular flap) is often the most appropriate definitive soft tissue management. Free flaps provide a large volume of vascularized tissue, excellent padding, and can cover complex defects, offering the best chance for wound healing and infection prevention.
Question 84
Topic: Lower Extremity Trauma
A 45-year-old male with isolated medial compartment knee osteoarthritis and a varus mechanical axis is undergoing a medial opening-wedge high tibial osteotomy (HTO). To achieve optimal unloading, where should the weight-bearing line be transposed in the coronal plane?
Correct Answer & Explanation
. Through the Fujisawa point (62% of the tibial plateau width from the medial edge)
Explanation
The goal of an HTO for medial compartment OA is to shift the mechanical axis into slight valgus. The optimal target is the Fujisawa point, located approximately 62% of the total tibial plateau width measured from the medial cortex.
Question 85
Topic: Lower Extremity Trauma
A resident is designing a custom intramedullary nail for a research study. To maximize the torsional and bending rigidity of the solid cylindrical nail, which of the following design modifications is most effective?
Correct Answer & Explanation
. Increasing the outer diameter by 1 mm
Explanation
The bending and torsional rigidity of a solid cylindrical implant are most significantly influenced by its radius. Biomechanically, bending rigidity is proportional to the radius to the fourth power, making an increase in outer diameter the most effective modification.
Question 86
Topic: Lower Extremity Trauma
A 45-year-old active laborer presents with medial knee pain. Radiographs reveal isolated medial compartment osteoarthritis and a mechanical axis that passes through the medial compartment. When planning a valgus-producing high tibial osteotomy (HTO), where should the target mechanical axis ideally pass?
Correct Answer & Explanation
. Through the lateral compartment at 62% of the tibial width from medial to lateral
Explanation
In a valgus-producing HTO for medial compartment OA, the target mechanical axis is typically shifted to the lateral compartment, approximately 62% of the tibial plateau width from medial to lateral (Fujisawa point). This effectively unloads the diseased medial compartment.
Question 87
Topic: Lower Extremity Trauma
During revision TKA, the surgeon encounters an isolated tight extension gap with a well-balanced flexion gap. Assuming the components are currently optimally sized, which of the following is the most appropriate surgical action?
Correct Answer & Explanation
. Release the posterior capsule from the femur
Explanation
A tight extension gap with a balanced flexion gap is addressed by releasing the posterior capsule or resecting more distal femur. Since resecting more bone elevates the joint line, posterior capsular release is often the preferred initial step.
Question 88
Topic: Lower Extremity Trauma
A 30-year-old female presents with a progressive genu valgum deformity. Preoperative planning reveals a Mechanical Lateral Distal Femoral Angle (mLDFA) of 95 degrees. All other joint orientation angles (MPTA, JLCA, LDTA) are within normal limits. Based on these findings, where is the primary anatomical location of the deformity?
Correct Answer & Explanation
. Distal femur
Explanation
Correct Answer: DThe Mechanical Lateral Distal Femoral Angle (mLDFA) is the lateral angle formed between the mechanical axis of the femur and the distal femoral joint line. Its normal value range is 85° to 90° (average 87°). A mLDFA of 95 degrees indicates that the distal femur is in valgus (an angle greater than 90 degrees for mLDFA signifies valgus, while an angle less than 85 degrees signifies varus). Since all other joint orientation angles are normal, the primary deformity is isolated to the distal femur.Options A, B, and C are incorrect because the MPTA, LDTA, and mLPFA (respectively) would be abnormal if the deformity were located in those segments. Option E is incorrect because a normal JLCA (Joint Line Convergence Angle) suggests no significant intra-articular pathology or ligamentous laxity contributing to the angular deformity.
Question 89
Topic: Lower Extremity Trauma
A resident is preparing to evaluate a patient for a lower extremity deformity correction using Paley's methodology. The first crucial step is to measure the Mechanical Axis Deviation (MAD). Which of the following accurately describes the correct technique for measuring MAD?
Correct Answer & Explanation
. Drawing a line from the center of the femoral head to the center of the talar dome on a standing, full-length, weight-bearing anteroposterior radiograph.
Explanation
Correct Answer: BAs explicitly stated in the teaching case, 'How to Measure the MAD: The patient must be positioned for a standing, full-length, weight-bearing anteroposterior (AP) radiograph (often called a teleoroentgenogram). A straight line is drawn from the exact center of the femoral head to the exact center of the talar dome in the ankle. This line represents the mechanical axis (or weight-bearing line) of the lower limb.'Option A is incorrect because MAD requires a standing, weight-bearing film and connects the femoral head to the talar dome, not the ASIS to the medial malleolus. Option C describes an angular measurement on a lateral view, not the MAD. Option D is incorrect as it uses different anatomical landmarks and a supine film. Option E describes a measurement from an MRI, which is not the standard method for determining global mechanical axis deviation on a radiograph.
Question 90
Topic: Lower Extremity Trauma
A 38-year-old male presents with chronic right knee pain and a progressive varus deformity. On weight-bearing full-length radiographs, the mechanical axis line of the lower extremity passes 20 mm medial to the center of the knee joint. Based on Paley's principles, what is the most accurate interpretation of this finding?
Correct Answer & Explanation
. The patient has a clinically significant varus deformity, leading to medial compartment overload.
Explanation
Correct Answer: CThe Mechanical Axis Deviation (MAD) is defined as the perpendicular distance from the mechanical axis line (femoral head to ankle plafond) to the center of the knee joint. A normal MAD passes slightly medial to the knee's center, typically by 8 mm (± 7 mm). In this patient, the mechanical axis passes 20 mm medial to the knee center. This value significantly exceeds the normal range, indicating a clinically significant varus or 'bow-legged' deformity. This medial deviation of the mechanical axis results in excessive load bearing on the medial compartment of the knee, predisposing to medial meniscus degeneration and unicompartmental osteoarthritis.Option A is incorrectbecause 20 mm medial deviation is well outside the normal physiologic range of 8 mm (± 7 mm).Options B and D are incorrectbecause while an abnormal MAD indicates a deformity, it does not, by itself, pinpoint the exact anatomic source (distal femur vs. proximal tibia). Further joint orientation angle assessment (e.g., mLDFA, MPTA) is required to localize the deformity.Option E is incorrectbecause a medial deviation of the mechanical axis indicates a varus deformity, not a valgus deformity. A valgus deformity would present with the mechanical axis passing lateral to the knee center.
Question 91
Topic: Lower Extremity Trauma
A 55-year-old female presents with left knee pain and a valgus deformity. Preoperative weight-bearing radiographs reveal a Mechanical Lateral Distal Femoral Angle (mLDFA) of 95° and a Medial Proximal Tibial Angle (MPTA) of 88°. All other joint orientation angles are within normal limits. Based on Paley's principles, where is the primary apex of the deformity located?
Correct Answer & Explanation
. Distal femur
Explanation
Correct Answer: DThe text states that the mLDFA (Mechanical Lateral Distal Femoral Angle) has a normal range of 85°-90°. An angle >90° indicates distal femoral valgus. In this patient, the mLDFA is 95°, which is significantly greater than 90°, indicating a valgus deformity originating in the distal femur. The MPTA (Medial Proximal Tibial Angle) has a normal range of 85°-90°. This patient's MPTA of 88° falls within the normal range, ruling out a primary deformity in the proximal tibia. Since all other angles are normal, the primary apex of the deformity is localized to the distal femur.Option A is incorrectbecause the MPTA is within the normal range.Option B is incorrectas the mLDTA (Mechanical Lateral Distal Tibial Angle) is not mentioned as abnormal.Option C is incorrectas the LPFA (Lateral Proximal Femoral Angle) is not mentioned as abnormal.Option E is incorrectas the JLCA (Joint Line Convergence Angle) is not mentioned as elevated, which would suggest intra-articular pathology.
Question 92
Topic: Lower Extremity Trauma
A surgeon is applying a circular external fixator for a tibial deformity correction. The following diagram illustrates the desired placement of the reference rings:
Based on the principles of tibial frame application, what is the critical requirement for the placement of the proximal and distal reference rings?
Correct Answer & Explanation
. They must be applied perfectly parallel to their respective joint lines to restore normal joint orientation angles.
Explanation
Correct Answer: BThe text, in the 'Tibial Frame Application' section, explicitly states: 'As this diagram illustrates, the reference rings must be applied perfectly parallel to their respective joint lines: ... This ring must be applied perfectly parallel to the knee joint line. ... This ring must be applied perfectly parallel to the ankle joint line.' It further explains, 'By securing these two rings parallel to the joints, the surgeon guarantees that when the connecting rods are made parallel (straightening the frame during the correction phase), the joint orientation angles (MPTA and mLDTA) will be automatically restored to their normal values.'Option A is incorrectbecause while the CORA is critical for hinge placement, the reference rings themselves are positioned relative to the joint lines, not necessarily at the CORA.Option C is incorrectbecause while maximizing the lever arm is important for stability, it must be balanced with respecting joint line parallelism and avoiding neurovascular structures.Option D is incorrectbecause both proximal and distal reference rings must be parallel to their respective joint lines, not perpendicular to the shaft.Option E is incorrectbecause ring placement is highly specific and follows strict anatomic and biomechanical rules, it is not arbitrary.
Question 93
Topic: Lower Extremity Trauma
A 45-year-old female presents with bilateral knee pain. A full-length standing AP radiograph is evaluated to assess alignment. The mechanical axis line is drawn from the center of the femoral head to the center of the ankle plafond. In a normally aligned lower extremity, where should this mechanical axis line intersect the knee joint?
Correct Answer & Explanation
. Approximately 8 mm to 10 mm medial to the center of the knee joint
Explanation
In normal coronal plane alignment, the lower extremity mechanical axis line does not pass exactly through the center of the knee. It typically passes slightly medial to the center, averaging 8 mm to 10 mm medial.
Question 94
Topic: Lower Extremity Trauma
A 55-year-old patient presents with a complex lower extremity deformity. Preoperative radiographs are obtained as shown below. Based on the provided case description and these images, which of the following statements best characterizes the primary deformities observed and their implications for surgical planning?
Correct Answer & Explanation
. The AP view (a) reveals severe genu valgum with a lateral mechanical axis deviation, while the lateral view (b) shows femoral procurvatum and tibial recurvatum, indicating multiple CORAs in both frontal and sagittal planes.
Explanation
Correct Answer: CThe case explicitly states the patient presents with 'femoral diaphyseal varus, distal metaphyseal valgus, and multilevel procurvatum, compounded by tibial valgus and proximal tibial recurvatum.' Image (a), the standing AP view, visually confirms severe genu valgum, which corresponds to a lateral mechanical axis deviation. Image (b), the lateral view, clearly shows femoral procurvatum (anterior bowing) and tibial recurvatum (posterior bowing). This combination of deformities across multiple bones and planes (frontal and sagittal) necessitates identifying multiple Centers of Rotation of Angulation (CORAs) and planning separate osteotomies for each apex, as emphasized by Paley's principles for complex, multi-apical deformities. This makes option C the most accurate and comprehensive description.Option A is incorrect because the AP view clearly shows genu valgum, not varum, and a lateral mechanical axis deviation, not medial. Option B incorrectly identifies the sagittal plane deformities; the case and image (b) show femoral procurvatum and tibial recurvatum, not the reverse. Option D is incorrect as the deformity is clearly multi-level and multi-planar, not isolated distal femoral valgus, and the lateral view shows significant sagittal plane deformities. Option E misinterprets the early postoperative image (c) and underestimates the complexity of the femoral deformity, which the case describes as profoundly complex and requiring meticulous, multi-level planning.
Question 95
Topic: Lower Extremity Trauma
Following a multi-level femoral osteotomy for severe valgus and procurvatum deformities, an intramedullary nail (IMN) is inserted. Postoperative radiographs, as shown in image (d) below, demonstrate the use of distal blocking screws. Given the preoperative distal femoral valgus that was corrected to varus, what is the correct placement and purpose of these blocking screws?
Correct Answer & Explanation
. Blocking screws are placed on the lateral side of the nail path to maintain the varus correction by pushing the distal segment medially.
Explanation
Correct Answer: BThe case explicitly states the rule for blocking screw placement: 'Always place blocking screws on the concave side of the deformity you are correcting.' For frontal plane corrections, to maintain a varus correction (which means pushing the distal segment medially to correct a preoperative valgus deformity), the blocking screw must be placed on thelateralside of the nail path. This creates an artificial inner cortex, forcing the nail medially and maintaining the desired varus alignment. Image (d) clearly shows the distal blocking screws placed laterally, consistent with maintaining a varus correction of a preoperative distal femoral valgus.Option A is incorrect because placing screws medially would maintain a valgus correction, which is the opposite of correcting a preoperative valgus to varus. Option C and D relate to sagittal plane corrections (procurvatum/recurvatum), where screws are placed anteriorly or posteriorly, respectively, and are not the primary function of the distal screws shown in the AP view for frontal plane correction. Option E is incorrect; while blocking screws contribute to overall stability, their primary role is to prevent angular loss of correction (the 'bell-clapper effect') by forcing the nail into a specific trajectory, not solely to prevent rotation.
Question 96
Topic: Lower Extremity Trauma
A 40-year-old male undergoes a FAN procedure for a severe femoral deformity. Postoperatively, a standing full-length radiograph reveals a Mechanical Lateral Distal Femoral Angle (mLDFA) of 80° and a Medial Proximal Tibial Angle (MPTA) of 95°. Based on the provided table of Joint Orientation Angles, what is the most accurate interpretation of these findings?
Correct Answer & Explanation
. The distal femur is in excessive varus, and the proximal tibia is in excessive valgus.
Explanation
Correct Answer: BThe case provides a table of Joint Orientation Angles with normal ranges and target goals:mLDFA (Mechanical Lateral Distal Femoral Angle):Normal range 85° - 90°, Target 88°. An mLDFA of 80° (less than 85°) indicates that the distal femur is angled more medially than normal, signifying a varus deformity of the distal femur.MPTA (Medial Proximal Tibial Angle):Normal range 85° - 90°, Target 87° - 90°. An MPTA of 95° (greater than 90°) indicates that the proximal tibia is angled more laterally than normal, signifying a valgus deformity of the proximal tibia.Therefore, the distal femur is in excessive varus, and the proximal tibia is in excessive valgus.Option A is incorrectbecause the mLDFA of 80° indicates varus, not valgus, of the distal femur.Option C is incorrectbecause the mLDFA of 80° indicates varus, not valgus, of the distal femur.Option D is incorrectbecause the MPTA of 95° indicates valgus, not varus, of the proximal tibia.Option E is incorrectbecause the mLDFA of 80° is outside the normal range (85°-90°) and indicates varus.
Question 97
Topic: Lower Extremity Trauma
A surgeon is planning a corrective osteotomy for a patient with a single-level angular deformity of the tibia. Preoperative planning identifies the CORA. To avoid a region of poor bone quality at the CORA, the surgeon decides to perform the osteotomy 3 cm distal to the CORA. The corrective hinge of the external fixator is accurately placed at the CORA. According to Paley's Osteotomy Rules, what is the expected outcome of this correction, and what challenge might it pose for subsequent intramedullary nailing?
Correct Answer & Explanation
. The mechanical axes will become collinear, but translation will occur at the osteotomy site, potentially complicating IM nailing.
Explanation
Correct Answer: CThis scenario directly describes Paley's Osteotomy Rule Two: 'When the corrective hinge is placed accurately at the CORA, but the actual osteotomy is performed at a different level (e.g., to avoid poor soft tissue, or for biological healing reasons), the axes will become collinear, but translation will inevitably occur at the osteotomy site.' The case further explains that 'this offset can make passing a rigid IM nail across the osteotomy site extremely difficult, or even impossible, if the translational offset is significant.'Option A is incorrectbecause translation will occur if the osteotomy is not at the CORA, even if the hinge is. Pure angulation without translation only occurs when both osteotomy and hinge are at the CORA (Rule One).Option B is incorrectbecause Rule Two states the axes will become collinear, not parallel but non-collinear. A secondary iatrogenic deformity with parallel but non-collinear axes occurs under Rule Three.Option D is incorrectbecause the rule describes translation, not overcorrection, and the difficulty for IM nailing is a direct consequence.Option E is incorrectbecause the rule describes the geometric outcome and challenge for IMN, not a failure of osteotomy healing due to CORA separation.
Question 98
Topic: Lower Extremity Trauma
A 28-year-old patient undergoes a FAN procedure for a complex multiapical tibial deformity. During the procedure, the external fixator is used to acutely correct the deformity. Intraoperative fluoroscopy confirms perfect alignment, with the mechanical axis passing directly through the center of the knee and ankle joints, and all joint orientation angles within normal limits. An intramedullary nail is then inserted. What is the *most significant* patient-centric advantage of this FAN approach compared to a traditional long-term external fixator for definitive correction?
Correct Answer & Explanation
. Reduced patient morbidity and improved overall recovery experience due to immediate removal of the external frame.
Explanation
Correct Answer: CThe case highlights 'Reduced Patient Morbidity' as a key advantage: 'Patients are completely freed from the physical restrictions, pain, and psychological burden of a long-term external frame, dramatically improving their overall recovery experience.' This is a direct patient-centric benefit of removing the external fixator immediately after the IM nail is placed.Option A is incorrectbecause while FAN offers 'Unmatched Precision,' the question asks for apatient-centricadvantage compared to a traditional external fixator. Traditional external fixators are also capable of precise angular correction, albeit over a longer period and with higher patient morbidity.Option B is incorrectbecause while the risk oflong-termpin-site infections is eliminated, pin-site infections can still occur during the temporary period the fixator is in place. The primary benefit is theremovalof the frame, not the complete elimination of infection risk during the temporary application.Option D is incorrectbecause while FAN can manage translation, this is a technical advantage, not themost significant patient-centricadvantage over a traditional fixator, which can also correct translation.Option E is incorrectbecause FAN often involves the cost of both an external fixator and an IM nail, potentially making it more expensive than a traditional external fixator alone, though the overall cost-benefit of faster recovery and reduced complications might be favorable.
Question 99
Topic: Lower Extremity Trauma
A patient has undergone a Fixator-Assisted Nailing (FAN) procedure for a complex lower extremity deformity. The images below represent typical post-operative radiographs following such a procedure. What do these images primarily confirm regarding the success of the FAN technique?
Correct Answer & Explanation
. The complete absence of any residual angular or translational deformity, with the correction locked in by an intramedullary nail.
Explanation
Correct Answer: BThe images provided (ch_142_fig_fbe55b.webp and ch_142_fig_fa46a4.webp) show an intramedullary nail in place, with the bone segments appearing well-aligned. The case describes FAN as a technique where 'The correction is meticulously confirmed with intraoperative fluoroscopy to ensure the MAD and all joint orientation angles are absolutely perfect. While the fixator rigidly holds the bone segments in this idealized position, an IM nail is passed across the osteotomy site, permanently locking in the correction internally. The external fixator is immediately removed at the end of the surgical case.' Therefore, these post-operative images confirm the successful acute correction and internal fixation of the deformity.Option A is incorrectbecause the external fixator is removed at the end of the FAN procedure; these images show internal fixation only.Option C is incorrectbecause the goal of FAN is definitive correction in one stage, not to require further immediate intervention.Option D is incorrectbecause the images show a well-aligned bone with an IM nail, which is the desired outcome, not an iatrogenic deformity.Option E is incorrectbecause FAN is a hybrid technique that uses atemporaryexternal fixator, not a traditional Ilizarov frame for long-term stabilization.
Question 100
Topic: Lower Extremity Trauma
A 55-year-old male presents with chronic right knee pain and a progressive valgus deformity. A weight-bearing long-leg anteroposterior radiograph is obtained, as depicted in the foundational diagram below, illustrating key alignment parameters. The mechanical axis is measured to pass 15 mm lateral to the center of the knee joint. The mLDFA is measured at 78°, and the MPTA is 88°.
Based on these findings and the principles of deformity correction, which of the following statements is TRUE?
Correct Answer & Explanation
. The mLDFA of 78° indicates a varus deformity of the distal femur, requiring a valgus-producing osteotomy.
Explanation
Correct Answer: CThe mechanical axis deviation (MAD) is the perpendicular distance from the center of the knee to the mechanical axis line. A negative MAD indicates the mechanical axis falls lateral to the center of the knee, which represents a valgus deformity. A MAD of -15 mm (15 mm lateral) is outside the neutral zone (0 ± 8 mm) and confirms a significant valgus deformity. The normal mLDFA is 85° to 90° (average 87°). An mLDFA of 78° is less than 85°, indicating a valgus deformity of the distal femur. The normal MPTA is 85° to 90° (average 87°). An MPTA of 88° is within the normal range, suggesting the proximal tibia is not the primary source of the frontal plane deformity.Option A is incorrect:A negative MAD indicates valgus, not physiologic varus, and -15 mm is outside the neutral zone.Option B is incorrect:The MPTA is normal, ruling out a primary deformity in the proximal tibia. A varus malalignment would be indicated by a positive MAD, not a negative one.Option D is incorrect:An mLDFA of 78° indicates a valgus deformity of the distal femur (less than 85°), not a varus deformity. Correction would require a varus-producing osteotomy (e.g., lateral closing wedge or medial opening wedge) to increase the mLDFA towards normal.Option E is incorrect:An MPTA of 88° is within the normal range (85°-90°), indicating no significant valgus deformity of the proximal tibia. Therefore, a medial opening wedge osteotomy of the tibia is not indicated based on this angle.
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