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8. Foot and Ankle MCQs

Practice Set 72 of 353

This practice set contains high-yield board review questions covering key concepts in 8. Foot and Ankle. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 1421

Topic: 8. Foot and Ankle

During a severe valgus correction of the proximal tibia using a medial closing wedge osteotomy, what is the most significant neurological risk, and what prophylactic measure is often considered?

. Saphenous nerve injury; prophylactic medial release.
. Deep peroneal nerve injury; prophylactic anterior compartment fasciotomy.
. Common peroneal nerve injury; prophylactic peroneal nerve decompression.
. Tibial nerve injury; prophylactic tarsal tunnel release.
. Sural nerve injury; prophylactic lateral release.

Correct Answer & Explanation

. Common peroneal nerve injury; prophylactic peroneal nerve decompression.

Explanation

Severe valgus corrections (especially those stretching the lateral structures) place the common peroneal nerve at high risk for stretch neuropraxia. Prophylactic peroneal nerve decompression is often recommended.

Question 1422

Topic: 8. Foot and Ankle

A 45-year-old male presents with a varus right knee. Full-length radiographs reveal a medial Mechanical Axis Deviation (MAD) of 25 mm. The mechanical Lateral Distal Femoral Angle (mLDFA) is 87° and the Medial Proximal Tibial Angle (MPTA) is 87°. The Joint Line Convergence Angle (JLCA) is 7° (apex lateral). What is the primary source of his varus malalignment?

. Distal femoral varus deformity.
. Proximal tibial varus deformity.
. Combined femoral and tibial diaphyseal bowing.
. Intra-articular deformity or collateral ligament laxity.
. Compensatory ankle malalignment.

Correct Answer & Explanation

. Intra-articular deformity or collateral ligament laxity.

Explanation

The normal mLDFA and MPTA indicate the bony segments are not the cause of the varus. An abnormal JLCA (>2°) in the presence of a medial MAD indicates intra-articular deformity or collateral ligament laxity.

Question 1423

Topic: 8. Foot and Ankle

A 16-year-old undergoes tibial lengthening using distraction osteogenesis with an Ilizarov frame. On postoperative day 20, he develops a foot drop and decreased sensation in the first dorsal web space. What is the most appropriate initial management?

. Stop the distraction process and place the ankle in a neutral or slightly plantarflexed position.
. Increase the distraction rate to relieve tension on the posterior compartment.
. Immediately perform a common peroneal nerve decompression at the fibular head.
. Remove the external fixator and convert to an intramedullary nail.
. Prescribe high-dose oral corticosteroids and continue lengthening at a slower rate.

Correct Answer & Explanation

. Stop the distraction process and place the ankle in a neutral or slightly plantarflexed position.

Explanation

Peroneal nerve palsy can occur during proximal tibial lengthening due to stretch. The immediate treatment is halting distraction and resting the nerve, often accompanied by plantarflexing the ankle to reduce tension.

Question 1424

Topic: 8. Foot and Ankle

A 35-year-old male is evaluated for post-traumatic ankle malalignment. To assess the distal tibial joint orientation in the coronal plane, the Lateral Distal Tibial Angle (LDTA) is measured. What is the standard normal value for the LDTA?

. 80 degrees
. 85 degrees
. 89 degrees
. 93 degrees
. 97 degrees

Correct Answer & Explanation

. 89 degrees

Explanation

The Lateral Distal Tibial Angle (LDTA) defines the coronal orientation of the ankle joint. A normal LDTA is 89°, with a typical range of 86° to 92°.

Question 1425

Topic: 8. Foot and Ankle

A 42-year-old male presents with post-traumatic ankle arthritis and a valgus deformity of the distal tibia. To determine the exact deformity, the surgeon measures the Lateral Distal Tibial Angle (LDTA). What is the normal expected value for the mechanical LDTA (mLDTA)?

. 80 degrees
. 84 degrees
. 89 degrees
. 93 degrees
. 96 degrees

Correct Answer & Explanation

. 89 degrees

Explanation

The normal mechanical Lateral Distal Tibial Angle (mLDTA) is 89 degrees (range 86 to 92 degrees). It is formed by the intersection of the tibial mechanical axis and the ankle joint orientation line.

Question 1426

Topic: 8. Foot and Ankle

When assessing Mechanical Axis Deviation (MAD) on a full-length standing radiograph to plan a deformity correction, the surgeon notes a MAD of 30 mm medial to the knee center. What is the most critical technical prerequisite of the radiograph to ensure accurate preoperative deformity planning?

. The beam must be centered strictly over the hip joint
. The patellae must be positioned pointing straight forward
. The patient must be completely non-weight-bearing
. The radiograph must be taken in a supine position
. Both ankles must be held in 15 degrees of internal rotation

Correct Answer & Explanation

. The patellae must be positioned pointing straight forward

Explanation

To accurately assess coronal plane deformities and joint orientation angles, the full-length standing radiograph must be taken with the patellae pointing straight forward (neutral rotation). Limb rotation significantly distorts the projected coronal alignment.

Question 1427

Topic: 8. Foot and Ankle
A surgeon is planning an opening wedge high tibial osteotomy for a patient with a proximal tibial varus deformity. The preoperative planning identifies a single CORA in the proximal tibial metaphysis. The surgeon aims for a perfect anatomical correction with no translation. Referring to the provided image, which diagram set (i, ii, iii, or iv) best illustrates the desired outcome if Paley's Rule One is strictly followed?
. A. Diagram set (b), Roman numeral (i)
. B. Diagram set (b), Roman numeral (ii)
. C. Diagram set (b), Roman numeral (iii)
. D. Diagram set (b), Roman numeral (iv)
. E. Diagram set (c), Roman numeral (i)

Correct Answer & Explanation

. A. Diagram set (b), Roman numeral (i)

Explanation

Paley's Rule One states: 'When the osteotomy is performed at the level of the CORA, and the Angulation Correction Axis (ACA) also passes exactly through the CORA, the result is pure angular correction with zero translation.' Diagram set (b) illustrates an opening wedge osteotomy. Within this set, Roman numeral (i) depicts the osteotomy line passing through the ACA-CORA, resulting in 37° angular correction, no MAD, perfect anatomic axis alignment, and normal ankle and knee joint orientation.

Question 1428

Topic: 8. Foot and Ankle

The ultimate goal of any frontal plane osteotomy around the knee is to restore the biomechanical language of the limb to its physiologic state. Which of the following statements accurately reflects the primary, non-negotiable objective of a frontal plane osteotomy around the knee, as emphasized by Paley's principles?

. A. To achieve a perfectly straight anatomical axis, regardless of the mechanical axis position.
. B. To eliminate all joint line convergence angles (JLCA) to prevent cartilage wear.
. C. To shift the mechanical axis back to its neutral, physiologic position, thereby reducing the Mechanical Axis Deviation (MAD) to zero.
. D. To ensure the Angulation Correction Axis (ACA) is always placed precisely at the Center of Rotation of Angulation (CORA).
. E. To achieve limb lengthening in all cases to address potential limb length discrepancies.

Correct Answer & Explanation

. C. To shift the mechanical axis back to its neutral, physiologic position, thereby reducing the Mechanical Axis Deviation (MAD) to zero.

Explanation

Correct Answer: CThe teaching case explicitly states: 'The fundamental, non-negotiable goal of a frontal plane osteotomy around the knee is to shift the mechanical axis back to its neutral, physiologic position, thereby reducing the MAD to zero.' This ensures that ground reaction forces are transmitted harmoniously through the center of the hip, knee, and ankle joints, preventing premature joint degeneration.Option A is incorrect because the mechanical axis, not just the anatomical axis, is the ultimate measure of weight transmission. A perfectly straight anatomical axis does not guarantee a neutral mechanical axis. Option B is incorrect; while JLCA is important, its elimination is not the primary goal of an osteotomy, and a normal JLCA is 0-2 degrees, not necessarily zero. Option D is incorrect; while placing the ACA at the CORA is ideal (Rule One), it's not always feasible or necessary, as Rule Two allows for correction with translation when the osteotomy is away from the CORA but the ACA is at the CORA. Option E is incorrect; limb lengthening is a secondary effect of opening wedge osteotomies and is only desirable if a limb length discrepancy exists; it is not a universal goal for all frontal plane osteotomies (closing wedge osteotomies shorten).

Question 1429

Topic: 8. Foot and Ankle

The mechanical axis deviation (MAD) is a critical parameter in lower limb deformity planning. In a normal lower extremity, where does the mechanical axis line typically pass in relation to the center of the knee joint?

. 10 to 15 mm lateral
. 1 to 3 mm lateral
. 1 to 8 mm medial
. 15 to 20 mm medial
. Directly through the center of the lateral compartment

Correct Answer & Explanation

. 1 to 8 mm medial

Explanation

In a mechanically neutral lower limb, the mechanical axis (a line from the center of the femoral head to the center of the ankle talus) passes slightly medial (1 to 8 mm) to the center of the knee joint.

Question 1430

Topic: 8. Foot and Ankle
A patient undergoes a high tibial osteotomy (HTO) and subsequently develops a foot drop. During which of the following steps is the common peroneal nerve at the highest risk of direct iatrogenic injury during a lateral closing-wedge HTO?
. Placement of the medial retractor
. Osteotomy of the proximal fibula
. Osteotomy of the medial tibial cortex
. Fixation of the plate on the anteromedial tibia
. Release of the superficial medial collateral ligament

Correct Answer & Explanation

. Osteotomy of the proximal fibula

Explanation

Lateral closing-wedge HTO typically requires a concomitant proximal fibular osteotomy to allow for tibial compression. The common peroneal nerve winds tightly around the fibular neck and is highly susceptible to injury during this step.

Question 1431

Topic: 8. Foot and Ankle

A patient undergoes a lateral closing-wedge high tibial osteotomy accompanied by a proximal fibular osteotomy. Postoperatively, the patient is unable to actively dorsiflex the ankle. Injury to which of the following structures most likely occurred?

. Tibial nerve
. Deep peroneal nerve
. Superficial peroneal nerve
. Common peroneal nerve
. Saphenous nerve

Correct Answer & Explanation

. Common peroneal nerve

Explanation

The common peroneal nerve is highly vulnerable during lateral closing-wedge HTO and proximal fibular osteotomies. Injury results in foot drop due to loss of ankle dorsiflexion and toe extension.

Question 1432

Topic: 8. Foot and Ankle

When performing a massive correction of tibia vara using an Ilizarov frame, a fibular osteotomy is generally required. Which level of the fibula is the safest and most commonly recommended to avoid peroneal nerve injury and distal tibiofibular instability?

. Proximal metaphysis
. Fibular neck
. Middle third of the diaphysis
. Distal syndesmosis
. Lateral malleolus

Correct Answer & Explanation

. Middle third of the diaphysis

Explanation

Osteotomy of the middle third of the fibula is safest. A proximal osteotomy heavily risks the common peroneal nerve, while a very distal osteotomy can compromise the syndesmosis and ankle stability.

Question 1433

Topic: 8. Foot and Ankle

A patient presents with a mechanical axis deviation (MAD) falling significantly medial to the knee center. Radiographic evaluation reveals a mechanical lateral distal femoral angle (mLDFA) of 87 degrees and a medial proximal tibial angle (MPTA) of 81 degrees. Where is the primary source of the varus deformity?

. Femur
. Tibia
. Knee joint (ligamentous laxity)
. Both femur and tibia
. Ankle joint

Correct Answer & Explanation

. Tibia

Explanation

Normal mLDFA is 87 degrees (85-90) and normal MPTA is 87 degrees (85-90). An MPTA of 81 degrees indicates proximal tibial varus, meaning the deformity is primarily tibial.

Question 1434

Topic: Ankle Trauma & Sports

During a significant correction of a proximal tibial angular deformity, a fibular osteotomy is planned to prevent tethering. Where is the most appropriate anatomical level for the fibular osteotomy to minimize the risk of peroneal nerve injury while effectively releasing the tether?

. Fibular neck
. Proximal metaphyseal-diaphyseal junction
. Middle and distal third junction
. Distal tibiofibular syndesmosis
. Lateral malleolus

Correct Answer & Explanation

. Middle and distal third junction

Explanation

Fibular osteotomies are typically performed at the junction of the middle and distal thirds of the fibula to minimize risk to the common peroneal nerve proximally and preserve the distal syndesmotic stability.

Question 1435

Topic: 8. Foot and Ankle

A 45-year-old male presents with a complex lower limb deformity requiring full-length standing radiographs for pre-operative planning. The orthopedic surgeon aims to minimize magnification and parallax errors and accurately assess the entire limb. Which of the following statements regarding the radiographic technique, as depicted in the image, is MOST accurate?

. The X-ray tube should be positioned 5 feet (152.5 cm) from the film cassette to optimize image quality.
. For comprehensive lower limb alignment, the X-ray beam should always be centered at the ankle to capture distal deformities.
. To evaluate forefoot and midfoot relationships, the X-ray beam should be centered at the level of the toes.
. The standard protocol dictates centering the X-ray beam at the hip for all full-length lower limb radiographs.
. Magnification errors are primarily minimized by using a smaller focal spot size, not by tube-to-cassette distance.

Correct Answer & Explanation

. The standard protocol dictates centering the X-ray beam at the hip for all full-length lower limb radiographs.

Explanation

Correct Answer: CThe case emphasizes the critical importance of standardized, high-quality, full-length, weight-bearing radiographs. The standard protocol for minimizing magnification and parallax errors dictates a 10-foot (305 cm) distance between the X-ray tube and the film cassette. The vertical positioning of the X-ray beam is equally critical depending on the specific area of interest. As stated in the text, 'When assessing specific distal deformities, the beam level must be adjusted: Level of the Toes: When evaluating forefoot and midfoot relationships.' Therefore, centering the beam at the level of the toes is correct for forefoot and midfoot assessment.Option A is incorrectbecause the standard protocol dictates a 10-foot (305 cm) distance, not 5 feet, to minimize magnification and parallax errors.Option B is incorrectbecause for comprehensive lower limb alignment, the beam is typically centered at the knee. While centering at the ankle is appropriate for specific distal deformities, it is not the general rule for comprehensive lower limb alignment.Option D is incorrectas the text specifies centering at the knee for comprehensive lower limb alignment, or at the ankle/toes for specific distal deformities, not routinely at the hip.Option E is incorrectbecause while focal spot size affects image sharpness, the primary method for minimizing magnification errors in full-length radiographs, as highlighted in the text, is the 10-foot (305 cm) tube-to-cassette distance.

Question 1436

Topic: 8. Foot and Ankle

A 30-year-old patient presents with a severe equinus contracture of the right ankle, making it impossible to place the foot flat on the ground for standard weight-bearing radiographs. The surgeon needs to assess the standing relationship between the foot and the tibia. Which of the following radiographic techniques, utilizing the principles illustrated in the images, is most appropriate for this scenario?

. Obtain a non-weight-bearing lateral ankle radiograph with the foot in maximal dorsiflexion.
. Perform a standard weight-bearing lateral foot radiograph, accepting the partial weight-bearing status.
. Utilize a radiolucent block to position the foot in a simulated standing, plantigrade position, and obtain a cross-table lateral view of the foot to include the tibia.
. Obtain a true lateral view of the ankle by overlapping the malleoli, regardless of the foot's position.
. Perform a CT scan of the ankle and foot, as radiographs are unreliable in severe equinus.

Correct Answer & Explanation

. Utilize a radiolucent block to position the foot in a simulated standing, plantigrade position, and obtain a cross-table lateral view of the foot to include the tibia.

Explanation

Correct Answer: CThe case explicitly addresses this scenario: 'Standard weight-bearing is impossible for patients with severe equinus or varus contractures... In these scenarios, simulated weight-bearing techniques must be employed using radiolucent blocks.' The text further details, 'If there is an equinus (a) or varus (b) deformity, the foot should be positioned on a board in a simulated standing position and a cross-table LAT view radiograph of the foot should be obtained. The foot must be placed on a radiolucent board in as close to a plantigrade position as possible.' This specialized radiograph is called a LAT foot to include tibia in simulated weight bearing, and it reveals the standing relationship between the foot and the tibia, as shown in the provided images.Option A is incorrectbecause a non-weight-bearing radiograph would not provide the crucial standing relationship between the foot and the tibia, which is essential for deformity planning.Option B is incorrectbecause the patient cannot achieve a plantigrade position, making a 'standard weight-bearing' lateral foot radiograph impossible or highly inaccurate for assessing true alignment.Option D is incorrectbecause while overlapping the malleoli is characteristic of a true lateral ankle view, the text specifies that for simulated weight-bearing, the foot should be positioned on a board in a simulated standing position, and the lateral malleolus is posterior to the medial malleolus in a properly positioned LAT foot to include tibia in simulated weight bearing, not necessarily overlapped.Option E is incorrectbecause while CT scans provide detailed 3D information, the case emphasizes the necessity and utility of specialized radiographic techniques for pre-operative planning in these situations, making radiographs a reliable and standard first-line assessment when performed correctly.

Question 1437

Topic: 8. Foot and Ankle

A 50-year-old patient undergoes a high tibial osteotomy for a varus knee deformity. Postoperatively, the full-length standing radiographs show that the mechanical axis has been successfully restored, passing through the center of the knee. However, the patient continues to experience pain, and follow-up imaging reveals early lateral compartment cartilage wear. Based on the principles discussed, what is the most likely reason for this suboptimal outcome?

. The osteotomy was performed too far from the CORA, leading to a translational deformity.
. The sagittal plane deformity was not adequately addressed during the correction.
. The X-ray beam was not centered at the knee during the pre-operative planning radiographs.
. The final plan restored the MAD but left the knee joint line significantly tilted.
. The patient had an undiagnosed femoral anteversion, which was not corrected.

Correct Answer & Explanation

. The final plan restored the MAD but left the knee joint line significantly tilted.

Explanation

Correct Answer: DThe text highlights the importance of joint line obliquity: 'Correcting the MAD is not enough if it leaves the knee or ankle joint line tilted. A joint line that is not parallel to the ground during weight-bearing will experience sheer forces, leading to rapid degeneration. Always ensure your final plan restores both the MAD and a horizontal joint line.' In this scenario, despite a corrected MAD, persistent pain and lateral compartment wear suggest that the joint line was left oblique, leading to abnormal shear forces and accelerated degeneration in the lateral compartment.Option A is incorrectbecause if the MAD was successfully restored, the translational deformity (if any) from an osteotomy away from the CORA would not be the primary cause of continued pain and new compartment wear, as the overall alignment would be correct.Option B is incorrectbecause while sagittal plane deformities are important, the specific presentation of early lateral compartment wear after successful MAD correction points more directly to coronal joint line obliquity rather than a sagittal issue.Option C is incorrectbecause if the MAD was successfully restored, it implies that the pre-operative planning, despite any potential initial radiographic flaws, ultimately led to a correct mechanical axis, so this is less likely the direct cause of the new problem.Option E is incorrectbecause femoral anteversion primarily affects rotational alignment and gait, not typically leading to early lateral compartment wear after successful coronal MAD correction, unless it significantly altered the joint line mechanics in an unaddressed way, which is less direct than joint line obliquity.

Question 1438

Topic: 8. Foot and Ankle

A 45-year-old male presents for evaluation of a lower limb deformity. As per Paley's principles, the initial step involves obtaining a standardized 51-inch standing bipedal radiograph. Which of the following patient positioning parameters is most critical to ensure accurate coronal plane measurements and neutralize rotational malalignment?

. Patient's feet pointing straight forward, regardless of patella position.
. Weight distributed primarily on the symptomatic limb.
. Patellae pointing directly anteriorly towards the x-ray tube.
. Knees slightly flexed to reduce joint space overlap.
. X-ray tube positioned at a 6-foot distance from the patient.

Correct Answer & Explanation

. Patellae pointing directly anteriorly towards the x-ray tube.

Explanation

Correct Answer: CThe text explicitly states: 'The absolute key to neutralizing rotational malalignment is the 'patella forward' position. The patellae must point directly anteriorly toward the x-ray tube, regardless of where the feet point. This ensures that any varus or valgus measurements are true representations of the coronal plane deformity, rather than artifacts created by hip rotation or tibial torsion.'Option A (Feet forward):This is incorrect. The text emphasizes that the patellae, not the feet, must point forward to neutralize rotation. Foot position is secondary.Option B (Weight on symptomatic limb):This is incorrect. The text specifies 'weight distributed evenly on both feet' for standardized imaging.Option C (Patellae forward):This is the correct answer, directly from the text.Option D (Knees slightly flexed):This is incorrect. Standardized radiographs are taken in full extension to assess true weight-bearing alignment.Option E (X-ray tube at 6-foot distance):This is incorrect. The text specifies a 'strict distance of 10 feet (3 meters)' to minimize geometric distortions.

Question 1439

Topic: 8. Foot and Ankle

A 55-year-old female presents with chronic right knee pain. A standardized 51-inch standing bipedal radiograph is obtained. . The overall limb mechanical axis is drawn from the center of the femoral head to the center of the ankle. This line is found to pass 25 mm medial to the geometric center of the knee joint. According to Paley's principles, what does this finding indicate?

. Normal physiological alignment.
. Valgus malalignment of the limb.
. Varus malalignment of the limb.
. An isolated distal femoral varus deformity.
. An isolated proximal tibial valgus deformity.

Correct Answer & Explanation

. Varus malalignment of the limb.

Explanation

Correct Answer: CThe text defines Mechanical Axis Deviation (MAD): 'Normal Alignment: The mechanical axis passes slightly medial to the center of the knee, typically 8 to 10 mm medial... Varus Malalignment (Bow-legged): The mechanical axis passes further medial to the knee center, often falling completely outside the medial joint compartment. The MAD is quantified as the absolute distance in millimeters from the knee center to the mechanical axis line (e.g., '25 mm medial MAD').' A MAD of 25 mm medial is significantly beyond the normal range (8-10 mm medial) and indicates a varus malalignment.Option A (Normal physiological alignment):Incorrect. Normal MAD is 8-10 mm medial. 25 mm medial is abnormal.Option B (Valgus malalignment):Incorrect. Valgus malalignment occurs when the mechanical axis passes lateral to the knee center.Option C (Varus malalignment):Correct. A mechanical axis passing significantly medial to the knee center indicates varus.Option D (Isolated distal femoral varus):Incorrect. While this could contribute, MAD only indicates overall limb alignment, not the specific bone or level of deformity. Further 'Malorientation Tests' are needed for that.Option E (Isolated proximal tibial valgus):Incorrect. Similar to D, MAD does not pinpoint the exact location of the deformity.

Question 1440

Topic: 8. Foot and Ankle

A resident is tasked with obtaining a 51-inch standing bipedal radiograph for a patient undergoing lower limb deformity analysis. The resident positions the patient correctly but inadvertently sets the X-ray tube distance at a standard 3-foot (approximately 1 meter) distance from the patient, rather than the recommended 10 feet (3 meters). What is the most likely consequence of this deviation from the strict imaging protocol?

. Reduced radiation exposure to the patient.
. Improved image resolution and clarity.
. Artificial magnification of anatomy and distortion of mechanical axis lines.
. Elimination of parallax errors in angular measurements.
. Inability to capture the entire lower extremity on a single cassette.

Correct Answer & Explanation

. Artificial magnification of anatomy and distortion of mechanical axis lines.

Explanation

Correct Answer: CThe text explicitly states: 'To minimize the geometric distortions of magnification and parallax, the x-ray tube must be positioned at a strict distance of 10 feet (3 meters) from the patient. This near-parallel beam geometry is crucial for the accuracy of angular and linear measurements. Radiographs taken at standard 3-foot or 6-foot distances will artificially magnify the anatomy and distort the mechanical axis lines.'Option A (Reduced radiation exposure):Incorrect. Closer distance typically means higher dose to achieve adequate image density, or the need for lower mAs, but the primary consequence mentioned is distortion.Option B (Improved image resolution):Incorrect. While closer might seem to improve resolution, the primary issue at a short distance is magnification and distortion, which negatively impact measurement accuracy.Option C (Artificial magnification and distortion):Correct. This is the direct consequence highlighted in the text.Option D (Elimination of parallax errors):Incorrect. Shorter distancesincreaseparallax errors, not eliminate them.Option E (Inability to capture entire extremity):Incorrect. The 51-inch cassette size is for capturing the entire limb, regardless of tube distance, though magnification would make it appear larger.

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