Menu

8. Foot and Ankle MCQs

Practice Set 69 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 1361

Topic: 8. Foot and Ankle



When analyzing a deformity on an anteroposterior (AP) radiograph of the ankle, the Lateral Distal Tibial Angle (LDTA) is commonly measured. What is the normal value for the LDTA, and what does a value of 80° signify?

. Normal is 89°; 80° signifies ankle valgus.
. Normal is 89°; 80° signifies ankle varus.
. Normal is 95°; 80° signifies ankle equinus.
. Normal is 80°; 80° is normal.
. Normal is 100°; 80° signifies syndesmotic rupture.

Correct Answer & Explanation

. Normal is 89°; 80° signifies ankle varus.

Explanation

The normal LDTA is approximately 89° (range 86-92°). An LDTA less than 85° indicates an angular deformity where the distal articular surface tilts proximally on the lateral side, which defines an ankle valgus deformity.

Question 1362

Topic: 8. Foot and Ankle

A 48-year-old male presents with a severe post-traumatic varus deformity of the distal tibia, leading to ankle joint degeneration. Preoperative planning reveals an LDTA of 80°. The CORA is identified just proximal to the ankle joint. The surgeon plans an acute correction using a locking plate. Which of the following statements accurately describes the significance of the LDTA in this case and the goal of correction?

. An LDTA of 80° indicates a proximal tibial varus, requiring a high tibial osteotomy.
. An LDTA of 80° indicates a distal tibial valgus, and correction aims to restore it to 85-90°.
. An LDTA of 80° indicates a distal tibial varus, and correction aims to restore it to 86-92°.
. An LDTA of 80° indicates a distal femoral valgus, requiring a distal femoral osteotomy.
. An LDTA of 80° is within the normal range, suggesting the deformity is intra-articular.

Correct Answer & Explanation

. An LDTA of 80° indicates a distal tibial varus, and correction aims to restore it to 86-92°.

Explanation

Correct Answer: CThe case content defines the Lateral Distal Tibial Angle (LDTA) as assessing the ankle joint orientation in the coronal plane, with a normal range of 86° to 92°. It states that"An abnormal LDTA indicates a distal tibial deformity, often leading to secondary ankle varus or valgus and rapid joint degeneration."An LDTA of 80° is less than the normal range, indicating a distal tibial varus deformity. The goal of correction would be to restore this angle to its normal range of 86-92°.Option A (An LDTA of 80° indicates a proximal tibial varus, requiring a high tibial osteotomy)is incorrect. Proximal tibial varus is assessed by the MPTA, not the LDTA.Option B (An LDTA of 80° indicates a distal tibial valgus, and correction aims to restore it to 85-90°)is incorrect. An angle less than the normal range (86-92°) indicates varus, not valgus. Also, the target range is 86-92°, not 85-90°.Option D (An LDTA of 80° indicates a distal femoral valgus, requiring a distal femoral osteotomy)is incorrect. Distal femoral valgus is assessed by the mLDFA, not the LDTA.Option E (An LDTA of 80° is within the normal range, suggesting the deformity is intra-articular)is incorrect. An LDTA of 80° is outside the normal range (86-92°), indicating a bony deformity, not necessarily an intra-articular one.

Question 1363

Topic: 8. Foot and Ankle

In a healthy adult with normal lower extremity alignment, what is the geometric relationship between the mechanical axis of the lower extremity and the anatomical axis of the femur?

. They are perfectly colinear and parallel.
. The anatomical axis is oriented in 7 degrees of varus relative to the mechanical axis.
. The anatomical axis is oriented in 7 degrees of valgus relative to the mechanical axis.
. The mechanical axis is oriented in 7 degrees of valgus relative to the anatomical axis.
. They intersect exactly at the center of the tibial plafond.

Correct Answer & Explanation

. The anatomical axis is oriented in 7 degrees of valgus relative to the mechanical axis.

Explanation

The normal mechanical axis of the lower extremity runs from the center of the femoral head to the center of the ankle mortise. The normal anatomical axis of the femur diverges by approximately 7 degrees of valgus relative to this mechanical axis.

Question 1364

Topic: 8. Foot and Ankle

A 12-year-old patient presents with a 'toeing-in' gait. On physical examination, with the patient prone and knees flexed to 90 degrees, the thigh-foot angle (TFA) is measured. The examiner notes that the axis of the foot is internally rotated by 5 degrees relative to the axis of the thigh. Based on the normal values provided in the case, what is the approximate total pathologic internal tibial torsion deformity in this patient?

. 5 degrees of internal tibial torsion.
. 10 degrees of external tibial torsion.
. 15 degrees of internal tibial torsion.
. 20 degrees of internal tibial torsion.
. 25 degrees of internal tibial torsion.

Correct Answer & Explanation

. 20 degrees of internal tibial torsion.

Explanation

Correct Answer: DThe case states that the normal Thigh-Foot Angle (TFA) is 10-15 degrees of external rotation. For calculation purposes, we can use an average normal value of 15 degrees external rotation. The patient's TFA is measured at 5 degrees ofinternalrotation. To find the total pathologic difference, we calculate the difference from the normal external rotation to the observed internal rotation.Normal TFA = 15 degrees external rotationObserved TFA = 5 degrees internal rotationTotal pathologic difference = (Normal External Rotation) + (Observed Internal Rotation)Total pathologic difference = 15° (external) + 5° (internal) = 20 degrees of internal tibial torsion.This calculation is directly analogous to the example provided in the case: 'If a patient's TFA measures 10 degrees ofinternalrotation, they have a total internal tibial torsion deformity of approximately 25 degrees relative to the normal population value (15° external to 10° internal represents a 25° total pathologic difference).'Options A, B, C, and E are incorrectas they do not correctly calculate the total pathologic difference from the normal external rotation to the observed internal rotation.

Question 1365

Topic: 8. Foot and Ankle

In the normal human tibia, what is the anatomical relationship between the mechanical axis and the anatomic axis in the coronal plane?

. They diverge by approximately 5 to 7 degrees.
. They intersect at the level of the tibial tubercle.
. They are parallel and virtually collinear.
. The mechanical axis lies 2 cm lateral to the anatomic axis.
. They intersect only at the ankle joint center.

Correct Answer & Explanation

. They are parallel and virtually collinear.

Explanation

Unlike the femur, where the anatomic and mechanical axes diverge by about 5 to 7 degrees, the anatomic and mechanical axes of the normal tibia are parallel and virtually collinear in the coronal plane.

Question 1366

Topic: 8. Foot and Ankle

A 50-year-old male with a severe varus deformity of the proximal tibia undergoes a large opening-wedge high tibial osteotomy. Postoperatively, he develops a foot drop and decreased sensation over the dorsum of his foot. Stretching of which of the following structures is the most likely cause?

. Tibial nerve
. Deep peroneal nerve only
. Common peroneal nerve
. Saphenous nerve
. Sural nerve

Correct Answer & Explanation

. Common peroneal nerve

Explanation

Large corrections of severe varus deformities, particularly with opening-wedge osteotomies, stretch the lateral structures. This places the common peroneal nerve at high risk of traction neuropathy, leading to foot drop and sensory loss over the foot dorsum.

Question 1367

Topic: 8. Foot and Ankle

Paley defines Mechanical Axis Deviation (MAD) as a primary metric for determining lower limb malalignment. How is MAD accurately measured on a standing long-leg anteroposterior radiograph?

. The angle formed between the femoral and tibial mechanical axes
. The perpendicular distance from the center of the knee joint to the mechanical axis line
. The degree of translation at the level of the joint line
. The distance between the anatomic axis of the femur and the mechanical axis of the tibia
. The angular difference between the mLDFA and the mMPTA

Correct Answer & Explanation

. The perpendicular distance from the center of the knee joint to the mechanical axis line

Explanation

Mechanical Axis Deviation (MAD) is a linear measurement. It is defined as the perpendicular distance (in millimeters) from the mechanical axis line (connecting the center of the femoral head to the center of the ankle) to the center of the knee joint.

Question 1368

Topic: 8. Foot and Ankle

A 50-year-old patient presents with a severe, multiplanar tibial malunion, as depicted in the clinical image below. The deformity includes significant angulation, translation, and a rotational component. The surgeon is preparing for a complex deformity correction. According to the teaching case, what is the absolute minimum requirement for initial radiographic assessment in this scenario?

. CT scan with 3D reconstruction of the tibia.
. MRI of the knee and ankle joints to assess cartilage damage.
. High-quality, standing, weight-bearing, full-length anteroposterior (AP) and lateral radiographs of the entire lower extremity.
. Stress radiographs of the ankle to assess ligamentous stability.
. Bilateral full-length standing radiographs for comparison.

Correct Answer & Explanation

. High-quality, standing, weight-bearing, full-length anteroposterior (AP) and lateral radiographs of the entire lower extremity.

Explanation

Correct Answer: CThe teaching case explicitly states under 'Preoperative Planning Masterclass: A Step-by-Step Guide': 'High-quality, standing, weight-bearing, full-length anteroposterior (AP) and lateral radiographs of the entire lower extremity are the absolute minimum requirement. These images must be well-calibrated (usually with a 50mm scaling ball) and show the hip, knee, and ankle on a single continuous film to prevent parallax error.'Options A and B (CT/MRI) are advanced imaging modalities that may be used for further detail but are not the 'absolute minimum requirement' for initial geometric planning. Option D (stress radiographs) assesses stability, not the primary deformity geometry. Option E (bilateral radiographs) is often helpful for comparison but the case specifies the 'absolute minimum requirement' for the affected limb's assessment.

Question 1369

Topic: 8. Foot and Ankle

A 25-year-old patient presents with a tibial shaft malunion, as seen in the clinical image below, resulting in a significant foot progression angle during gait. The orthopedic surgeon is assessing the rotational component of the deformity. According to the teaching case, what is the most practical and accurate clinical method for assessing tibial torsion?

. Observing the foot progression angle during normal gait.
. Measuring the rotational profile using a goniometer with the patient standing.
. Assessing the thigh-foot axis with the patient prone and knees flexed to 90 degrees.
. Performing a CT scan with specialized rotational measurements.
. Comparing the internal and external rotation of the hip joints.

Correct Answer & Explanation

. Assessing the thigh-foot axis with the patient prone and knees flexed to 90 degrees.

Explanation

Correct Answer: CThe teaching case states: 'Tibial torsion is more accurately assessed by observing the orientation of the long axis of the sole of the foot relative to the knee forward position. This can best be achieved using the thigh-foot axis with the patient prone and the knees flexed to 90 degrees.' It also cautions that 'the foot progression angle may appear normal, even in the presence of a severe torsional deformity, because of compensatory mechanisms at the hip or knee.'Option A is incorrect because, as stated in the case, the foot progression angle can be misleading due to compensatory mechanisms. Option B is a general assessment but less specific and accurate for tibial torsion than the thigh-foot axis. Option D (CT scan) is a radiographic method, and while accurate, the question asks for the 'most practical and accurateclinicalmethod.' Option E assesses hip rotation, not specifically tibial torsion.

Question 1370

Topic: 8. Foot and Ankle

Preoperative assessment for a complex lower extremity deformity requires standardized, high-quality radiographs. Which of the following is a mandatory characteristic of these radiographs for accurate planning, as emphasized in the case?

. Non-weight-bearing views to avoid joint compression artifacts.
. Short-segment views focusing only on the deformity apex.
. Rotationally uncontrolled views to capture maximum deformity.
. Full-length, weight-bearing, and rotationally controlled views.
. Only AP views are necessary, as lateral views can be misleading.

Correct Answer & Explanation

. Full-length, weight-bearing, and rotationally controlled views.

Explanation

Correct Answer: DThe text explicitly lists the 'Non-Negotiables: Clinical and Radiographic Assessment': 'Standardized, high-quality, orthogonal AP and lateral radiographs are mandatory. They must be: Full-length: To visualize the entire mechanical axis from the center of the hip to the center of the ankle. Weight-bearing: To assess the limb's alignment under physiological load, which unmasks ligamentous laxity (JLCA alterations). Rotationally controlled: With the patella facing strictly forward (AP view) to eliminate rotational artifact, which can falsely project as coronal or sagittal angulation.'Option A is incorrectas weight-bearing views are crucial to assess alignment under physiological load.Option B is incorrectas full-length views are necessary to visualize the entire mechanical axis.Option C is incorrectas rotationally controlled views are essential to eliminate rotational artifact.Option E is incorrectas both AP and lateral orthogonal views are mandatory for assessing 3D deformities.

Question 1371

Topic: 8. Foot and Ankle

A 35-year-old male is currently undergoing lengthening of the left tibia using a circular external fixator. The distraction rate is set at 1.0 mm per day, divided into four increments. Three weeks into distraction, he develops an inability to actively dorsiflex his toes and reports decreased sensation in the first web space. What is the most appropriate initial management?

. Increase the distraction rate to relieve tension on the nerve.
. Administer oral corticosteroids and continue the current distraction rate.
. Stop distraction immediately and slightly compress the frame.
. Schedule immediate surgical decompression of the tarsal tunnel.
. Perform a prophylactic fasciotomy.

Correct Answer & Explanation

. Stop distraction immediately and slightly compress the frame.

Explanation

The patient is experiencing signs of a common peroneal nerve palsy, a known complication of proximal tibial lengthening. The immediate treatment is to stop distraction and shorten (compress) the frame slightly to relieve tension on the nerve.

Question 1372

Topic: 8. Foot and Ankle

A 12-year-old girl is undergoing significant lengthening of her tibia. To prevent one of the most common and debilitating joint contracture complications associated with this procedure, the surgeon must either fix the foot in the frame or institute an aggressive physical therapy protocol. Which specific deformity is the surgeon primarily trying to prevent?

. Knee flexion contracture
. Knee extension contracture
. Ankle equinus contracture
. Ankle calcaneus contracture
. Metatarsophalangeal hyperextension

Correct Answer & Explanation

. Ankle equinus contracture

Explanation

Ankle equinus contracture is the most common joint contracture during tibial lengthening due to the relative resistance and tension of the gastrocnemius-soleus complex. Prophylactic measures include splinting the foot in neutral or incorporating the foot into the external fixator.

Question 1373

Topic: 8. Foot and Ankle

During a 6-cm tibial lengthening using an Ilizarov frame, a surgeon routinely secures the distal tibiofibular syndesmosis with a transverse wire. What is the primary purpose of this specific technical step?

. To prevent nonunion of the tibial corticotomy.
. To prevent proximal migration of the lateral malleolus and subsequent ankle valgus.
. To stimulate early fibular consolidation.
. To prevent deep vein thrombosis in the calf.
. To inhibit common peroneal nerve stretch.

Correct Answer & Explanation

. To prevent proximal migration of the lateral malleolus and subsequent ankle valgus.

Explanation

During tibial lengthening, the distal fibula can migrate proximally due to the pull of intact soft tissues, leading to a shortened lateral malleolus and a secondary valgus deformity of the ankle. Fixing the distal tibiofibular syndesmosis prevents this complication.

Question 1374

Topic: 8. Foot and Ankle

During preoperative planning for a distal tibial deformity, the mechanical axis line is found to fall outside the knee joint completely, and the CORA is located 3 cm proximal to the ankle joint. To avoid creating an unexpected translational deformity, how should the external fixator hinges be aligned?

. Perpendicular to the anatomical axis of the distal tibia
. Co-linear with the exact location of the CORA
. Proximal to the CORA by 2 cm to allow for soft tissue clearance
. Directly over the anticipated osteotomy site, regardless of the CORA
. Parallel to the joint line of the ankle

Correct Answer & Explanation

. Co-linear with the exact location of the CORA

Explanation

To prevent secondary translational deformities (Paley's Rule 1 and 2), the axis of the hinges of the external fixator must be placed directly collinear with the CORA in the specific plane of the deformity.

Question 1375

Topic: 8. Foot and Ankle

When planning a deformity correction using the magnitude of deformity (angle), the intersection of the proximal and distal axes forms the CORA. Which plane requires the measurement of the Mechanical Lateral Distal Tibial Angle (mLDTA) for standard limb alignment assessment?

. Sagittal plane
. Coronal plane
. Axial plane
. Oblique plane
. Transverse plane

Correct Answer & Explanation

. Coronal plane

Explanation

The mLDTA (normal ~89°) is measured on an AP (coronal plane) radiograph and represents the angle between the tibial mechanical axis and the ankle joint line in the coronal plane.

Question 1376

Topic: 8. Foot and Ankle

During correction of a complex foot deformity using a Taylor Spatial Frame, what defines the "origin" of the virtual hinge in the frame's software?

. The physical center of the proximal ring
. The geometric center of the specific bone segment being moved
. The CORA of the deformity
. The midpoint between the master and dependent rings
. The most distal strut attachment point

Correct Answer & Explanation

. The CORA of the deformity

Explanation

In six-axis hexapod frames like the TSF, the software requires the definition of a virtual hinge, which should correspond to the CORA (Center of Rotation of Angulation) to ensure anatomical correction.

Question 1377

Topic: 8. Foot and Ankle

A 70-year-old female presents with a chronic varus knee deformity. Preoperative planning includes obtaining full-length weight-bearing radiographs. The mechanical axis is drawn from the center of the femoral head to the center of the ankle joint. This line passes 20 mm medial to the center of the knee joint. What does this measurement represent, and what is its significance?

. The Joint Line Convergence Angle (JLCA), indicating intra-articular cartilage loss.
. The Medial Proximal Tibial Angle (MPTA), indicating a proximal tibial varus.
. The Mechanical Axis Deviation (MAD), quantifying the magnitude of the varus deformity and joint loading.
. The Center of Rotation of Angulation (CORA), indicating the apex of the deformity.
. The Posterior Proximal Tibial Angle (PPTA), indicating altered tibial slope.

Correct Answer & Explanation

. The Mechanical Axis Deviation (MAD), quantifying the magnitude of the varus deformity and joint loading.

Explanation

Correct Answer: CThe text defines the mechanical axis as a line from the center of the femoral head to the center of the ankle joint. The perpendicular distance from the center of the knee joint to this mechanical axis line is the Mechanical Axis Deviation (MAD). A normal MAD is typically 8-10 mm medial to the center of the knee. A MAD of 20 mm medial signifies a significant varus deformity, quantifying the magnitude of the problem and indicating increased medial compartment loading. Calculating the MAD is described as 'the first, most critical step in any deformity analysis' as it 'quantifies the magnitude of the problem' and 'directly informs the magnitude of the surgical correction required to neutralize joint-loading forces.' The image shows a full-length radiograph, which is necessary for MAD measurement.Option A is incorrectbecause JLCA measures ligamentous laxity or cartilage loss within the knee joint, not the overall mechanical axis deviation.Option B is incorrectbecause MPTA is an angle that evaluates proximal tibial coronal alignment, not the linear distance of the mechanical axis from the knee center.Option D is incorrectbecause CORA is the intersection of proximal and distal axes of a deformed bone, indicating the epicenter of angulation, not the overall mechanical axis deviation.Option E is incorrectbecause PPTA evaluates proximal tibial sagittal alignment (tibial slope), not coronal plane mechanical axis deviation.

Question 1378

Topic: 8. Foot and Ankle

A 50-year-old patient presents with a long-standing diaphyseal tibial malunion characterized by varus angulation in the coronal plane and anterior translation (procurvatum) in the sagittal plane. Which of the following is a direct biomechanical consequence of the anterior translation component of this deformity?

. Increased compressive forces on the medial compartment of the knee.
. Chronic tensile strain on the lateral collateral ligament (LCL).
. Altered patellofemoral tracking and increased anterior cruciate ligament (ACL) strain.
. Compensatory subtalar eversion and asymmetrical ankle wear.
. Decreased posterior tibial slope, leading to reduced anterior tibial translation.

Correct Answer & Explanation

. Altered patellofemoral tracking and increased anterior cruciate ligament (ACL) strain.

Explanation

Correct Answer: CThe case describes a diaphyseal tibial malunion with varus angulation (coronal plane) and anterior translation (procurvatum) in the sagittal plane. The text specifically addresses the consequences of this combined deformity: 'An anterior translation of the distal tibia (procurvatum) effectively increases the posterior tibial slope, altering the tension on the anterior cruciate ligament (ACL) and changing patellofemoral tracking, often leading to anterior knee pain and patellar maltracking.' The image illustrates the concept of multiplanar deformities with angulation and translation components in different planes.Option A and B are incorrectbecause these are direct consequences of the varus angulation component (coronal plane deformity), not the anterior translation (sagittal plane deformity).Option D is incorrectbecause compensatory subtalar eversion and asymmetrical ankle wear are typically consequences of the varus angulation extending to the ankle, not primarily the anterior translation.Option E is incorrectbecause anterior translation (procurvatum) effectively increases the posterior tibial slope, which leads to increased, not reduced, anterior tibial translation.

Question 1379

Topic: 8. Foot and Ankle

During tibial lengthening using distraction osteogenesis via an Ilizarov frame, which of the following is the most common joint contracture encountered?

. Knee flexion contracture
. Knee extension contracture
. Ankle dorsiflexion contracture
. Ankle plantarflexion (equinus) contracture
. Hip flexion contracture

Correct Answer & Explanation

. Ankle plantarflexion (equinus) contracture

Explanation

Ankle equinus is the most common contracture during tibial lengthening. It occurs due to the relative resistance and tension of the strong gastrocnemius-soleus complex compared to the anterior compartment musculature.

Question 1380

Topic: 8. Foot and Ankle

In a structurally normal femur, the anatomic axis diverges from the mechanical axis by approximately how many degrees?

. 0 degrees (they are collinear)
. 3 degrees
. 7 degrees
. 12 degrees
. 15 degrees

Correct Answer & Explanation

. 7 degrees

Explanation

The normal femoral mechanical axis is a line from the center of the femoral head to the center of the ankle joint. The anatomic axis (intramedullary canal) typically diverges from this mechanical axis by about 7 degrees of valgus.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page