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8. Foot and Ankle MCQs

Practice Set 67 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 1321

Topic: 8. Foot and Ankle

A 55-year-old patient with a history of a distal tibia fracture presents with chronic ankle pain and a noticeable limb length discrepancy. Full-length standing radiographs show a Mechanical Axis Deviation (MAD) of +20mm (medial to the center of the knee) and an LDTA of 84°. The ADTA is measured at 77°.

Based on these findings and Paley's principles, which of the following best describes the primary deformities present and their implications for surgical planning?

. The patient has a distal tibial recurvatum and a valgus ankle deformity, requiring a closing wedge osteotomy.
. The patient has a distal tibial procurvatum and a varus ankle deformity, requiring an opening wedge osteotomy.
. The patient has a distal tibial varus and a recurvatum deformity, contributing to medial ankle overload and anterior impingement.
. The patient has a distal tibial valgus and a procurvatum deformity, contributing to lateral ankle overload and posterior impingement.
. The MAD indicates a femoral deformity, which should be corrected first, irrespective of the tibial angles.

Correct Answer & Explanation

. The patient has a distal tibial varus and a recurvatum deformity, contributing to medial ankle overload and anterior impingement.

Explanation

Correct Answer: CLet's break down the findings based on Paley's principles:Mechanical Axis Deviation (MAD) of +20mm (medial to the center of the knee):A positive MAD medial to the knee indicates an overall varus alignment of the lower extremity.LDTA of 84°:The normal LDTA range is 86° to 92°. An LDTA of 84° is decreased, indicating a distal tibial varus deformity in the coronal plane. This varus angulation would contribute to increased pressure on the medial ankle joint, leading to medial ankle overload.ADTA of 77°:The normal ADTA range is 78° to 82°. An ADTA of 77° is decreased, indicating a distal tibial recurvatum deformity in the sagittal plane. Distal tibial recurvatum can lead to anterior ankle impingement.Therefore, the patient has a combination of distal tibial varus and recurvatum deformities, which explain the medial ankle overload and potential anterior impingement symptoms.Option A is incorrect because an LDTA of 84° indicates varus, not valgus, and recurvatum is correct but the valgus part is wrong. Option B is incorrect because an ADTA of 77° indicates recurvatum, not procurvatum. Option D is incorrect as the LDTA indicates varus, not valgus, and ADTA indicates recurvatum, not procurvatum. Option E is incorrect; while MAD is important, it doesn't exclusively indicate a femoral deformity, and tibial deformities (as evidenced by abnormal LDTA and ADTA) are clearly present and require attention.

Question 1322

Topic: 8. Foot and Ankle

A 38-year-old patient presents with a long-standing valgus deformity of the distal tibia. Clinical examination reveals a plantigrade foot despite the ankle deformity. Which of the following best describes the biomechanical compensation occurring at the subtalar joint to achieve this plantigrade position, as illustrated in the diagram?

. The subtalar joint pronates to maintain a plantigrade foot.
. The subtalar joint everts, leading to a valgus hindfoot.
. The subtalar joint supinates, moving into a varus position.
. The subtalar joint remains neutral, with compensation occurring at the midfoot.
. The subtalar joint dorsiflexes, shifting weight to the heel.

Correct Answer & Explanation

. The subtalar joint supinates, moving into a varus position.

Explanation

Correct Answer: CThe teaching case explicitly states, 'To counteract this and maintain a functional stance, the subtalar joint instinctively supinates, moving into a varus position to keep the foot plantigrade.' This is a critical compensatory mechanism for a valgus ankle deformity. The diagram further illustrates this, showing a valgus ankle (center) and the subsequent subtalar varus compensation (right) to achieve a plantigrade foot.Option A is incorrectbecause pronation of the subtalar joint would exacerbate the valgus alignment of the foot, making it impossible to achieve a plantigrade position in the presence of a valgus ankle deformity. The foot would be forced into excessive pronation, with the lateral border lifting off the ground.Option B is incorrectbecause eversion of the subtalar joint is synonymous with pronation, which would worsen the valgus alignment and prevent a plantigrade foot.Option D is incorrectbecause the subtalar joint is the primary adapter for hindfoot alignment. While midfoot compensation can occur, the initial and most significant compensation for a valgus ankle to maintain a plantigrade foot occurs at the subtalar joint.Option E is incorrectbecause dorsiflexion is a sagittal plane motion of the ankle joint, not a primary compensatory mechanism of the subtalar joint for coronal plane valgus deformity to achieve a plantigrade foot.

Question 1323

Topic: 8. Foot and Ankle

A 55-year-old female presents with chronic lateral ankle pain and progressive deformity. Standing AP radiographs of the ankle reveal a Lateral Distal Tibial Angle (LDTA) of 78°. Based on Paley's principles, what does this measurement signify, and what is the magnitude of the primary deformity?

. A varus deformity of 11°.
. A valgus deformity of 11°.
. A varus deformity of 14°.
. A valgus deformity of 14°.
. A neutral alignment with a normal LDTA.

Correct Answer & Explanation

. A valgus deformity of 14°.

Explanation

Correct Answer: DThe teaching case defines the normal Lateral Distal Tibial Angle (LDTA) as 89° ± 3° (86-92°). It explicitly states, 'An LDTA < 86° indicates avalgusdeformity of the distal tibia.' In this patient, the LDTA is 78°. The magnitude of the deformity is calculated by subtracting the measured LDTA from the normal value of 89°. Therefore, 89° - 78° = 11°. The case also provides an example: 'An LDTA of 75° signifies a massive 14° valgus deformity.' This implies that the deviation from 89 degrees is the magnitude of the deformity. So, 89 - 78 = 11 degrees. However, the options are 11 and 14. Let's re-read the example: 'An LDTA of 75° signifies a massive 14° valgus deformity originating in the supramalleolar tibia.' This means 89 - 75 = 14. So, for 78 degrees, it would be 89 - 78 = 11 degrees. Let's re-evaluate the options. If the normal range is 86-92, and 89 is the ideal, then 78 is 11 degrees less than the ideal. The question asks for the magnitude of the primary deformity. So, 11 degrees valgus is the correct magnitude. Let me re-check the options and my calculation. Ah, I see the error in my thought process. The options are 11 or 14. The calculation is 89 - 78 = 11. So, it's an 11° valgus deformity. The example of 75° leading to 14° valgus (89-75=14) confirms this calculation method. Therefore, 11° valgus is the correct answer.Option A is incorrectbecause an LDTA of 78° is less than the normal range, indicating a valgus, not varus, deformity.Option B is incorrectbecause while it correctly identifies a valgus deformity, the magnitude is 11°, not 14°.Option C is incorrectbecause it incorrectly identifies a varus deformity and the magnitude is incorrect for the given LDTA.Option E is incorrectbecause an LDTA of 78° is significantly outside the normal range of 86-92°, indicating a clear deformity.

Question 1324

Topic: 8. Foot and Ankle

A 42-year-old male presents with a severe left ankle valgus deformity. Preoperative planning includes the radiographic series shown. The unstressed long axial view (b) reveals a varus hindfoot, and the stressed eversion view (c) shows only partial correction of this varus. Based on these findings, what is the most appropriate interpretation regarding the subtalar compensation?

. The subtalar compensation is entirely flexible and will spontaneously correct after supramalleolar osteotomy (SMO).
. The subtalar compensation is entirely fixed and requires subtalar arthrodesis.
. The subtalar compensation has a fixed component due to chronic soft tissue and bony changes.
. The varus hindfoot is an independent deformity unrelated to the ankle valgus.
. The stressed eversion view is inconclusive and requires further dynamic imaging.

Correct Answer & Explanation

. The subtalar compensation has a fixed component due to chronic soft tissue and bony changes.

Explanation

Correct Answer: CThe teaching case emphasizes the critical distinction between flexible and fixed subtalar compensation. It states, 'The ability of the calcaneus to correct back to a neutral or valgus position [on the stressed eversion view] determines the surgical strategy. Failure to correct, or only partial correction, confirms a fixed soft-tissue contracture that must be addressed surgically.' In this scenario, the unstressed view shows varus (compensation), and the stressed view shows only partial correction. This directly indicates that the compensation is not entirely flexible and has developed a fixed component due to chronic changes in soft tissues (medial contracture) and potentially joint remodeling.Option A is incorrectbecause partial correction on the stressed eversion view contradicts the idea of entirely flexible compensation. If it were entirely flexible, it would fully correct to neutral or valgus.Option B is incorrectbecause while a fixed component exists, it doesn't automatically necessitate subtalar arthrodesis. The case outlines other joint-preserving options for partially fixed contractures, such as subtalar release and gradual distraction, or calcaneal osteotomies, depending on the specific nature of the fixation.Option D is incorrectbecause the case explicitly links the subtalar varus to the ankle valgus as a compensatory mechanism: 'A varus angle in the setting of an ankle valgus deformity signifies active subtalar compensation.'Option E is incorrectbecause the stressed eversion view is described as 'the master key to differentiating between flexible and fixed compensation,' making it a conclusive diagnostic tool in this context.

Question 1325

Topic: 8. Foot and Ankle

A 60-year-old patient with a chronic valgus ankle deformity undergoes a supramalleolar osteotomy (SMO) to correct the distal tibial alignment. Preoperative assessment failed to adequately identify a fixed subtalar varus compensation. Postoperatively, the patient experiences severe lateral column pain, difficulty achieving a plantigrade foot, and early signs of peroneal tendinopathy. What is the most likely cause of these postoperative complications?

. Overcorrection of the tibial valgus, leading to a varus ankle.
. Inadequate correction of the tibial valgus, resulting in persistent ankle valgus.
. Failure to address the fixed subtalar varus, leading to a rigidly non-plantigrade foot.
. Development of a new iatrogenic translation deformity due to incorrect CORA placement.
. Non-union of the supramalleolar osteotomy.

Correct Answer & Explanation

. Failure to address the fixed subtalar varus, leading to a rigidly non-plantigrade foot.

Explanation

Correct Answer: CThe teaching case explicitly warns against this critical error: 'If a surgeon performs an isolated Supramalleolar Osteotomy (SMO) to correct the tibial valgus without addressing a now-fixed subtalar varus, the result is catastrophic. The newly straightened ankle mortise will be forced onto a foot that is rigidly locked in varus. The patient will be completely unable to get their foot flat, walking entirely on the lateral border. This leads to severe lateral column overload, intractable pain, peroneal tendinopathy, and inevitable stress fractures of the fifth metatarsal.' The patient's symptoms directly match this description.Option A is incorrectbecause overcorrection to a varus ankle would typically cause medial column pain, not lateral column pain and a rigidly varus foot.Option B is incorrectbecause inadequate correction of the tibial valgus would mean the ankle remains in valgus, which would not typically lead to a rigidly varus foot and lateral column overload in the manner described.Option D is incorrectbecause while incorrect CORA placement can lead to iatrogenic translation, the specific constellation of symptoms (rigidly non-plantigrade foot, lateral column pain, peroneal tendinopathy) is most directly linked to the unaddressed fixed subtalar varus.Option E is incorrectbecause non-union would primarily cause pain at the osteotomy site and instability, not the specific hindfoot malalignment and lateral column symptoms described.

Question 1326

Topic: 8. Foot and Ankle

A 28-year-old patient presents with a complex valgus ankle deformity and suspected fixed subtalar compensation. To accurately diagnose and plan surgical correction, which of the following radiographic views is considered the 'absolute gold standard' for visualizing global hindfoot alignment and assessing the relationship between the longitudinal axis of the tibia and the calcaneus?

. Standing Anteroposterior (AP) Radiograph of the Ankle.
. Standing Lateral Radiograph of the Ankle and Foot.
. Unstressed Standing Long Axial View (Cobey-Saltzman View).
. Stressed Eversion View of the Hindfoot.
. Non-weight-bearing CT scan of the ankle.

Correct Answer & Explanation

. Unstressed Standing Long Axial View (Cobey-Saltzman View).

Explanation

Correct Answer: CThe teaching case explicitly states: 'TheUnstressed Standing Long Axial View (Cobey-Saltzman View): This is the absolute gold standard for visualizing global hindfoot alignment. It provides a direct, unobstructed view of the relationship between the longitudinal axis of the tibia and the calcaneus.' This view is crucial for identifying subtalar compensation.Option A is incorrectbecause the Standing AP Ankle view is foundational for measuring LDTA and assessing the primary supramalleolar deformity, but it does not provide the 'absolute gold standard' for global hindfoot alignment relative to the tibia.Option B is incorrectbecause the Standing Lateral Radiograph assesses sagittal plane alignment (ADTA, calcaneal pitch) but is not the primary view for coronal hindfoot alignment.Option D is incorrectbecause while the Stressed Eversion View is critical for differentiating flexible from fixed compensation, it is a dynamic stress view, not the 'absolute gold standard' for visualizing the static global hindfoot alignment itself. It builds upon the information from the unstressed long axial view.Option E is incorrectbecause the case emphasizes the importance ofweight-bearingradiographs for capturing true alignment and compensation, and a non-weight-bearing CT scan would mask the true extent of deformity and compensation.

Question 1327

Topic: 8. Foot and Ankle
A 35-year-old patient with a valgus ankle deformity (LDTA = 60°) also presents with 15° of fixed subtalar varus, as confirmed by stressed eversion views. The subtalar joint shows early arthritic changes. The surgeon plans a supramalleolar osteotomy (SMO) to correct the tibial deformity. Considering the fixed and arthritic subtalar joint, which of the following adjunct procedures, as illustrated in the diagram, would be the most appropriate to address the hindfoot?
. Isolated subtalar release and gradual distraction (ii).
. Medial displacement calcaneal osteotomy (MDCO) (c).
. Lateral closing wedge calcaneal osteotomy (vi).
. Subtalar arthrodesis (iii).
. No additional hindfoot procedure is needed if the SMO is perfectly performed.

Correct Answer & Explanation

. Subtalar arthrodesis (iii).

Explanation

The teaching case outlines the surgical algorithm for complex valgus ankle deformity, specifically addressing fixed subtalar varus. It states: 'Subtalar Arthrodesis: For severe, rigidly fixed, and arthritic subtalar joints that cannot be salvaged, a subtalar fusion is the definitive procedure.' The patient's presentation of 'fixed subtalar varus' and 'early arthritic changes' directly points to subtalar arthrodesis as the most appropriate and definitive solution, as depicted in option (iii) of the diagram.

Question 1328

Topic: 8. Foot and Ankle

In the context of supramalleolar valgus deformity, the Center of Rotation of Angulation (CORA) is a crucial geometric point for surgical planning. Where is the CORA typically located in the vast majority of supramalleolar deformities?

. Mid-diaphysis of the tibia.
. Proximal metaphysis of the tibia, far from the ankle joint.
. Very close to the ankle joint, often residing deep within the distal metaphysis or directly inside the joint line itself.
. Within the talus, distal to the ankle joint.
. At the level of the subtalar joint.

Correct Answer & Explanation

. Very close to the ankle joint, often residing deep within the distal metaphysis or directly inside the joint line itself.

Explanation

Correct Answer: CThe teaching case explicitly states: 'In the vast majority of supramalleolar deformities, the CORA is located very close to the ankle joint. It often resides deep within the distal metaphysis or, in severe cases, directly inside the joint line itself.' This anatomical reality is what makes the application of Paley's Osteotomy Rule 2 so critical, as a direct osteotomy at an intra-articular CORA is not feasible.Option A is incorrectbecause the mid-diaphysis is too far proximally for a supramalleolar deformity, which is by definition located just above the malleoli.Option B is incorrectfor the same reason as A; the CORA for a supramalleolar deformity is distal, not proximal and far from the ankle joint.Option D is incorrectbecause the CORA is defined for the deformed bone itself (the tibia in this case), not for an adjacent bone like the talus.Option E is incorrectbecause the CORA is related to the primary angular deformity of the tibia, not the subtalar joint, although the subtalar joint compensates for the tibial deformity.

Question 1329

Topic: 8. Foot and Ankle

A 48-year-old patient presents with a severe, multiplanar valgus ankle deformity, poor skin quality around the ankle, and a partially fixed subtalar varus contracture. The surgeon plans a supramalleolar osteotomy (SMO). Given these specific patient characteristics, which surgical technique for the SMO is most appropriate?

. Medial opening wedge osteotomy with internal plate fixation.
. Lateral closing wedge osteotomy with internal plate fixation.
. Percutaneous osteotomy with gradual correction using a circular external fixator.
. Ankle arthrodesis with internal fixation.
. Distal tibial osteotomy with intramedullary nail fixation.

Correct Answer & Explanation

. Percutaneous osteotomy with gradual correction using a circular external fixator.

Explanation

Correct Answer: CThe teaching case provides clear indications for different SMO techniques: 'Complex cases featuring significant multiplanar deformity, poor skin quality, or fixed soft tissue contractures are best managed with a percutaneous osteotomy and gradual correction using a circular external fixator (such as the Ilizarov apparatus or Taylor Spatial Frame). This method minimizes soft tissue stripping, preserves the periosteal blood supply, and allows for precise, postoperative fine-tuning of the correction while protecting delicate neurovascular structures.' The patient's presentation directly matches these indications.Option A and B are incorrectbecause internal fixation (medial opening wedge or lateral closing wedge with plating) is generally reserved for 'simpler, flexible deformities with excellent soft tissue envelopes.' This patient has a complex, multiplanar deformity, poor skin quality, and fixed contractures, making internal fixation less suitable due to higher risks of wound complications and inability to gradually correct fixed soft tissue issues.Option D is incorrectbecause ankle arthrodesis is a salvage procedure for severe ankle arthritis, not a deformity correction technique for a valgus ankle with a potentially salvageable joint. The question implies correction of the deformity, not fusion.Option E is incorrectbecause intramedullary nailing is typically used for diaphyseal fractures or deformities, not for precise angular and translational correction of a metaphyseal supramalleolar deformity, especially one requiring gradual correction and soft tissue management.

Question 1330

Topic: 8. Foot and Ankle

A 50-year-old patient with a severe left ankle valgus deformity undergoes comprehensive preoperative evaluation. The unstressed long axial view (b) shows a varus hindfoot, and the stressed eversion view (c) demonstrates only partial correction. Clinically, the patient exhibits severe lateral translation of the foot and a prominent medial malleolus (d, e). Following a supramalleolar osteotomy (SMO) and successful gradual distraction of the subtalar joint using an external fixator, what specific radiographic and clinical findings would confirm a successful realignment of the heel relative to the tibia?

. A postoperative AP radiograph showing an LDTA of 75° and a persistent varus hindfoot on the long axial view.
. A postoperative lateral radiograph showing increased calcaneal pitch and a prominent medial malleolus.
. A postoperative long axial view confirming complete realignment of the heel relative to the tibia, with resolution of lateral translation, and a plantigrade foot clinically.
. A postoperative stressed eversion view showing no change from the preoperative stressed view.
. A postoperative AP radiograph showing a JLCA of 5° and continued lateral column pain.

Correct Answer & Explanation

. A postoperative long axial view confirming complete realignment of the heel relative to the tibia, with resolution of lateral translation, and a plantigrade foot clinically.

Explanation

Correct Answer: CThe 'Clinical Masterclass Case Study' section directly addresses the desired outcome: 'The post-correction AP radiograph (h) shows the ankle joint is perfectly realigned and no longer inclined. The long axial view (i) confirms complete realignment of the heel relative to the tibia—the translation is resolved. Finally, the clinical photograph (j) shows a beautifully realigned, plantigrade foot.' Therefore, a postoperative long axial view showing corrected hindfoot alignment and clinical evidence of a plantigrade foot and resolved lateral translation are the key indicators of success.Option A is incorrectbecause an LDTA of 75° indicates persistent valgus deformity, and a persistent varus hindfoot means the subtalar compensation was not adequately addressed, indicating failure, not success.Option B is incorrectbecause increased calcaneal pitch is a sagittal plane measurement and does not directly confirm coronal plane hindfoot realignment. A prominent medial malleolus postoperatively would suggest persistent lateral translation or inadequate correction.Option D is incorrectbecause if the stressed eversion view showed no change, it would mean the fixed subtalar varus was not corrected, leading to a poor outcome.Option E is incorrectbecause a JLCA of 5° indicates persistent joint incongruity or subluxation, and continued lateral column pain is a hallmark of unaddressed fixed subtalar varus, signifying failure.

Question 1331

Topic: 8. Foot and Ankle

A 35-year-old male presents with chronic ankle pain and progressive deformity. Standing radiographs reveal a distal tibial valgus deformity with a Lateral Distal Tibial Angle (LDTA) of 60 degrees. The Center of Rotation of Angulation (CORA) is identified at the level of the ankle joint line. The surgeon plans a supramalleolar osteotomy (SMO) in the distal tibial metaphysis, approximately 3 cm proximal to the joint line, with the axis of correction (hinge) placed mathematically at the CORA. Which of Paley's Osteotomy Rules is being applied, and what is the expected biomechanical outcome?

. Option A: Rule One; pure angular correction with no secondary translation.
. Option B: Rule One; angular correction combined with unplanned translation.
. Option C: Rule Two; angular correction combined with planned, simultaneous translation.
. Option D: Rule Two; pure angular correction with no secondary translation.
. Option E: Rule Three; angular correction accompanied by an unplanned, secondary translation deformity.

Correct Answer & Explanation

. Option C: Rule Two; angular correction combined with planned, simultaneous translation.

Explanation

Correct Answer: CThe case describes a scenario where the osteotomy (bone cut) is performed in the distal tibial metaphysis (3 cm proximal to the joint line), but the axis of correction (hinge) is placed at the CORA (at the ankle joint line). This is the classic application of Paley's Rule Two. Rule Two states that if the hinge is placed at the CORA but the osteotomy is performed at a different level (above or below the CORA), the result is angular correction combined with a planned, simultaneous translation of the bone fragments. This is the most common and critical scenario for a supramalleolar osteotomy (SMO) to realign the mechanical axis over the center of the talus without cutting through articular cartilage.Option A is incorrectbecause Rule One applies when both the osteotomy and the hinge are placed exactly at the CORA, resulting in pure angular correction without translation. This is not the case here as the osteotomy is proximal to the CORA.Option B is incorrectbecause it misstates the outcome of Rule One and incorrectly applies it to this scenario.Option D is incorrectbecause while Rule Two is correctly identified, the outcome described (pure angular correction with no secondary translation) is characteristic of Rule One, not Rule Two.Option E is incorrectbecause Rule Three applies when both the osteotomy and the hinge are placed away from the CORA, leading to an unplanned, secondary translation deformity and a zigzag alignment. This represents poor surgical planning and is not the intended outcome in this scenario.

Question 1332

Topic: 8. Foot and Ankle

A 48-year-old patient presents with a long-standing distal tibial deformity. A standing full-length orthoroentgenogram is obtained. The image below illustrates the typical compensatory mechanism seen in such deformities. Based on the principles of deformity correction, what does the right panel of the image most accurately depict regarding the relationship between the distal tibia and the hindfoot?

. Option A: A normal limb alignment with a congruent mechanical axis through the ankle and subtalar joints.
. Option B: A 30° varus deformity of the distal tibia with a compensatory 30° subtalar eversion.
. Option C: A 30° valgus deformity of the distal tibia (LDTA = 60°) with a compensatory 30° subtalar inversion to maintain a plantigrade foot.
. Option D: A fixed 30° subtalar varus contracture unmasked by a perfectly aligned distal tibia.
. Option E: An iatrogenic zigzag deformity resulting from an osteotomy performed away from the CORA.

Correct Answer & Explanation

. Option C: A 30° valgus deformity of the distal tibia (LDTA = 60°) with a compensatory 30° subtalar inversion to maintain a plantigrade foot.

Explanation

Correct Answer: CThe right panel of the provided image clearly illustrates a 'zigzag' alignment. The distal tibia is angled in valgus (indicated by the medial shift of the mechanical axis and the angle of the tibia relative to the foot). The text explicitly states, 'On the right, a 30° valgus deformity (LDTA = 60°) is shown. The subtalar joint has inverted 30° to bring the plantar surface of the foot parallel to the ground, demonstrating full and flexible compensation.' This perfectly matches the description in Option C.Option A is incorrectas it describes the normal limb alignment, which is depicted in the left panel, not the right.Option B is incorrectbecause the image shows a valgus tibial deformity, not varus, and the compensation for valgus is inversion, not eversion.Option D is incorrectbecause the image depicts acompensatorysubtalar inversion, implying flexibility (as stated in the text 'demonstrating full and flexible compensation'), not a fixed contracture that has been unmasked. Unmasking occurs after tibial correction, not before.Option E is incorrectbecause the image illustrates a natural compensatory mechanism (the zigzag phenomenon) for an existing deformity, not an iatrogenic deformity caused by poor surgical planning (which would be an application of Paley's Rule Three).

Question 1333

Topic: 8. Foot and Ankle

A 55-year-old patient presents with a 30° valgus deformity of the distal tibia (LDTA = 60°). Clinical examination reveals a compensatory varus hindfoot. To determine the flexibility of the subtalar joint, a maximum eversion stress radiograph is performed. The image below shows the initial state (a) and the stress test (b.i). If the stress view (b.i) demonstrates that the foot can only evert by 15° despite maximum force, what is the most appropriate surgical plan?

. Option A: Perform a full 30° varus-producing supramalleolar osteotomy (SMO) to correct the tibia to an LDTA of 90°.
. Option B: Perform a 15° varus-producing SMO, intentionally leaving a 15° residual tibial valgus (LDTA = 75°).
. Option C: Perform a 30° varus-producing SMO combined with a subtalar fusion to address the fixed contracture.
. Option D: Perform a 30° varus-producing SMO and rely on aggressive postoperative physical therapy to stretch the fixed contracture.
. Option E: Perform a 45° varus-producing SMO to overcorrect the tibia and compensate for the fixed contracture.

Correct Answer & Explanation

. Option B: Perform a 15° varus-producing SMO, intentionally leaving a 15° residual tibial valgus (LDTA = 75°).

Explanation

Correct Answer: BThe case describes a 30° valgus tibial deformity. The stress eversion radiograph showing only 15° of eversion indicates a fixed 15° subtalar varus contracture (30° initial compensation - 15° flexible motion = 15° fixed contracture). According to the 'Calculated Compromise - Partially Fixed Contracture' section, the surgical plan in this scenario is to perform a planned, partial correction of the distal tibial deformity. The magnitude of the tibial correction must be strictly limited to the amount of available, flexible motion in the subtalar joint. Therefore, a 15° varus-producing SMO is performed, intentionally under-correcting the tibia to leave 15° of residual tibial valgus (LDTA = 75°). This residual tibial valgus will then be perfectly balanced by the fixed 15° subtalar varus contracture, resulting in a stable, plantigrade foot.Option A is incorrectbecause a full 30° correction would unmask the 15° fixed subtalar varus contracture, leaving the patient with a non-plantigrade foot locked in 15° varus.Option C is incorrectbecause while subtalar fusion is an option for severe, painful fixed contractures, the primary strategy described for a partially fixed contracture is a planned partial tibial correction to achieve a plantigrade foot without necessarily fusing the subtalar joint, especially if the goal is to preserve motion.Option D is incorrectbecause aggressive physical therapy is unlikely to overcome a fixed bony or capsular contracture of this magnitude and would not be the primary surgical strategy for achieving a plantigrade foot.Option E is incorrectbecause overcorrection would lead to a new deformity, potentially creating a valgus hindfoot or further destabilizing the ankle, and is not a recognized strategy for managing fixed subtalar contractures.

Question 1334

Topic: 8. Foot and Ankle

A 62-year-old patient presents with end-stage ankle osteoarthritis secondary to a long-standing distal tibial varus deformity. The mechanical axis deviation (MAD) passes significantly medial to the center of the ankle joint. According to Paley's principles, what is the primary reason for correcting the MAD in this patient's distal tibia?

. Option A: To improve the cosmetic appearance of the limb and make it look straighter.
. Option B: To prevent the progression of knee osteoarthritis by realigning the overall limb axis.
. Option C: To redistribute load-bearing forces evenly across the ankle plafond and prevent further asymmetric cartilage wear.
. Option D: To increase the range of motion of the ankle joint by decompressing the articular surfaces.
. Option E: To facilitate easier placement of an ankle arthroplasty in the future.

Correct Answer & Explanation

. Option C: To redistribute load-bearing forces evenly across the ankle plafond and prevent further asymmetric cartilage wear.

Explanation

Correct Answer: CThe case explicitly states, 'Correcting the deformity is not simply an aesthetic endeavor to make the bone look straight; it is a joint-salvage operation. The primary goal is restoring a neutral mechanical axis to redistribute forces evenly across the plafond.' When the MAD shifts the weight-bearing axis asymmetrically across the ankle plafond, it creates focal points of immense, localized pressure, leading to asymmetric cartilage wear, subchondral sclerosis, and progression of osteoarthritis. Therefore, redistributing load-bearing forces evenly is the primary goal.Option A is incorrectbecause while cosmetic improvement may occur, it is explicitly stated not to be the primary goal; joint salvage is.Option B is incorrectbecause while overall limb alignment can affect the knee, the question specifically refers to the MAD in thedistal tibiaand its effect on theankle joint. A distal tibial deformity primarily affects the ankle, not the knee, unless there are concomitant proximal deformities.Option D is incorrectbecause correcting MAD primarily addresses load distribution and joint preservation, not necessarily increasing the range of motion, especially in an already arthritic joint.Option E is incorrectbecause while a well-aligned limb might make future arthroplasty technically easier, the primary goal of a deformity correction is joint salvage and preventing the need for arthroplasty, or at least delaying it, by preserving the native joint.

Question 1335

Topic: 8. Foot and Ankle

A 28-year-old patient presents with a distal tibial valgus deformity and a compensatory varus hindfoot. The surgeon is performing a clinical examination to assess the flexibility of the subtalar joint. Which of the following steps is most critical to ensure accurate assessment of subtalar motion, isolating it from midfoot motion?

. Option A: Have the patient stand and observe their foot posture during gait.
. Option B: Perform a single-leg heel raise test to assess calf strength.
. Option C: Grasp the forefoot and lock the transverse tarsal joint (Chopart's joint) by inverting the calcaneus while assessing forefoot abduction/adduction relative to the hindfoot.
. Option D: Measure the ankle dorsiflexion and plantarflexion with a goniometer.
. Option E: Palpate the peroneal tendons for tenderness and stability.

Correct Answer & Explanation

. Option C: Grasp the forefoot and lock the transverse tarsal joint (Chopart's joint) by inverting the calcaneus while assessing forefoot abduction/adduction relative to the hindfoot.

Explanation

Correct Answer: CThe case explicitly details the hands-on assessment for diagnosing fixed vs. flexible contractures: 'Grasp the forefoot and lock the transverse tarsal joint (Chopart's joint) by inverting the calcaneus and assessing forefoot abduction/adduction relative to the hindfoot. This ensures you are isolating subtalar motion, not midfoot motion.' This step is crucial for accurately measuring the true range of motion of the subtalar joint without confounding contributions from the midfoot.Option A is incorrectbecause observing gait provides a dynamic assessment of overall function and compensation but does not quantify isolated subtalar flexibility.Option B is incorrectbecause a single-leg heel raise test assesses calf strength and hindfoot stability, but not the passive range of motion or flexibility of the subtalar joint.Option D is incorrectbecause measuring ankle dorsiflexion and plantarflexion assesses tibiotalar joint motion, not subtalar joint motion.Option E is incorrectbecause palpating peroneal tendons assesses for tendinopathy or instability, which is part of a general foot and ankle exam, but not specific to quantifying subtalar flexibility.

Question 1336

Topic: Midfoot & Hindfoot

A 50-year-old patient with a history of trauma presents with a complex distal tibial deformity. Preoperative planning involves identifying the Center of Rotation of Angulation (CORA). Why is identifying the CORA considered the single most important step in preoperative templating and planning for angular deformity correction?

. Option A: It determines the optimal length of the external fixator pins.
. Option B: It dictates the ideal location for the axis of correction (the 'hinge' of the osteotomy).
. Option C: It helps in assessing the patient's bone quality for hardware selection.
. Option D: It predicts the exact amount of bone graft needed for the osteotomy gap.
. Option E: It identifies the presence of a fixed subtalar contracture.

Correct Answer & Explanation

. Option B: It dictates the ideal location for the axis of correction (the 'hinge' of the osteotomy).

Explanation

Correct Answer: BThe case states: 'Identifying the CORA is the single most important step in preoperative templating and planning. The location of the CORA dictates the ideal location for the axis of correction (the 'hinge' of your osteotomy).' This is fundamental to applying Paley's osteotomy rules correctly and achieving the desired correction without creating secondary deformities.Option A is incorrectbecause while external fixator pin placement is related to the osteotomy, the CORA's primary role is not to determine pin length but the hinge location.Option C is incorrectbecause bone quality assessment is a separate consideration, typically done through imaging and clinical evaluation, not directly determined by the CORA.Option D is incorrectbecause the CORA helps plan the angular correction and translation, which in turn might influence the osteotomy gap, but it doesn't directly predict the amount of bone graft needed. The gap size is a consequence of the correction, not the primary purpose of CORA identification.Option E is incorrectbecause identifying a fixed subtalar contracture is done through clinical examination and stress radiographs, not by identifying the CORA of the tibial deformity.

Question 1337

Topic: 8. Foot and Ankle

A 38-year-old patient presents with a distal tibial valgus deformity. After thorough clinical and radiographic assessment, it is determined that the subtalar joint has *fully flexible* compensation. The surgeon plans a full correction of the distal tibial deformity via a supramalleolar osteotomy (SMO). What is the expected outcome of this surgical approach?

. Option A: The patient will likely develop a fixed subtalar varus contracture postoperatively.
. Option B: The tibia will be perfectly aligned, but the foot will remain in a compensatory varus position, leading to a non-plantigrade foot.
. Option C: A perfectly aligned tibia and a neutral, plantigrade foot that automatically adjusts to the new tibial position.
. Option D: The ankle joint will become unstable due to overcorrection of the deformity.
. Option E: The patient will require a secondary subtalar fusion to achieve a plantigrade foot.

Correct Answer & Explanation

. Option C: A perfectly aligned tibia and a neutral, plantigrade foot that automatically adjusts to the new tibial position.

Explanation

Correct Answer: CThis scenario corresponds to 'Scenario 1: The Green Light - Fully Flexible Compensation.' The text states: 'If the amount of eversion you can manually achieve is equal to or greater than the magnitude of the tibial deformity, the compensation is fully flexible.' In this case, the surgical plan is 'Full correction of the distal tibial deformity via a supramalleolar osteotomy (SMO).' The expected outcome is 'A perfectly aligned tibia and a neutral, plantigrade foot that automatically adjusts to the new tibial position.' This is because the flexible subtalar joint can naturally accommodate the corrected tibial alignment.Option A is incorrectbecause a fully flexible joint will not develop a fixed contracture as a direct result of correcting the proximal deformity; rather, a fixed contracture is a pre-existing condition that would be unmasked if not accounted for.Option B is incorrectbecause this outcome describes the 'nightmare scenario' where afixedsubtalar contracture is unmasked by full tibial correction. This is not the case with fully flexible compensation.Option D is incorrectbecause a properly planned and executed SMO for a fully flexible compensation aims to restore normal alignment and stability, not create instability.Option E is incorrectbecause a secondary subtalar fusion is typically considered for fixed, painful contractures that cannot be managed by partial tibial correction or if the subtalar joint itself is arthritic. It is not necessary when the compensation is fully flexible.

Question 1338

Topic: 8. Foot and Ankle
A 68-year-old patient presents with a long-standing distal tibial deformity. The image below illustrates a surgical strategy for managing a specific type of subtalar compensation. Based on this diagram and the case description, what do Panels (iii) and (iv) demonstrate as the intended outcome of this surgical approach?
. Full correction of a 30° tibial valgus deformity to an LDTA of 90° with a neutral hindfoot.
. An unmasked 15° fixed subtalar varus contracture after full tibial correction, resulting in a non-plantigrade foot.
. A planned, partial 15° supramalleolar osteotomy (SMO) leaving a 15° residual tibial valgus (LDTA = 75°), perfectly balancing a 15° fixed subtalar varus contracture to achieve a plantigrade foot.
. An overcorrection of the distal tibia to 45° of varus to compensate for a severe valgus hindfoot.
. The creation of a new zigzag deformity due to an osteotomy performed away from the CORA and hinge.

Correct Answer & Explanation

. A planned, partial 15° supramalleolar osteotomy (SMO) leaving a 15° residual tibial valgus (LDTA = 75°), perfectly balancing a 15° fixed subtalar varus contracture to achieve a plantigrade foot.

Explanation

This image and scenario directly correspond to 'Scenario 2: The Calculated Compromise - Partially Fixed Contracture.' Panels (iii) & (iv) show the result of a planned, partial 15° supramalleolar osteotomy. The tibia is deliberately left with a 15° valgus deformity (LDTA = 75°), which perfectly balances the 15° fixed subtalar varus, yielding a functional, plantigrade foot.

Question 1339

Topic: 8. Foot and Ankle

A 70-year-old patient, as shown in the clinical image, presents with a long-standing distal tibial deformity and significant ankle pain. The patient reports difficulty walking on uneven surfaces and a feeling of instability. Preoperative assessment reveals a fixed subtalar varus contracture of 10 degrees, in addition to a 20-degree valgus deformity of the distal tibia (LDTA = 70°). If the surgeon proceeds with a full 20-degree varus-producing supramalleolar osteotomy (SMO) to correct the tibia to an LDTA of 90°, what is the most likely immediate postoperative consequence for the patient?

. Option A: The patient will achieve a perfectly plantigrade foot with a neutral hindfoot.
. Option B: The patient's ankle range of motion will significantly improve, especially in dorsiflexion.
. Option C: The patient will experience a significant reduction in ankle pain due to restored mechanical axis.
. Option D: The patient will awaken with a non-plantigrade foot, locked in a 10-degree varus position, unable to bear weight flat on the floor.
. Option E: The patient will require immediate subtalar fusion to correct the newly created deformity.

Correct Answer & Explanation

. Option D: The patient will awaken with a non-plantigrade foot, locked in a 10-degree varus position, unable to bear weight flat on the floor.

Explanation

Correct Answer: DThis question describes the 'nightmare scenario' highlighted in the case. The patient has a 20° valgus tibial deformity and afixed10° subtalar varus contracture. If the surgeon performs a full 20° correction of the tibia, the 10° fixed subtalar varus contracture will be unmasked. The tibia will be straight (LDTA = 90°), but the foot will remain locked in 10° of varus relative to the now-straight tibia, making it non-plantigrade and unable to bear weight flat on the floor. The case explicitly states: 'The surgeon congratulates themselves on a beautiful X-ray. However, the patient awakens from surgery with a perfectly aligned tibia, but their foot is now locked in a severe, rigid 30° varus position, completely unable to bear weight flat on the floor. The surgical correction of the tibia has unmasked the fixed subtalar contracture, rendering the patient worse off than before surgery.'Option A is incorrectbecause a fixed contracture will prevent a perfectly plantigrade foot if the tibia is fully corrected.Option B is incorrectbecause while correcting the mechanical axis can improve joint mechanics, the immediate consequence of an unmasked fixed contracture would be severe functional impairment, not improved range of motion.Option C is incorrectbecause while restoring the mechanical axis is a goal, the immediate consequence of an unmasked fixed contracture would be new, severe pain and functional disability due to the non-plantigrade foot, outweighing any benefit from tibial alignment alone.Option E is incorrectbecause while subtalar fusion might eventually be considered, it is not animmediaterequirement or themost likely immediate consequenceof the initial surgery. The immediate consequence is the unmasked deformity.

Question 1340

Topic: 8. Foot and Ankle

When evaluating a patient with an acquired ankle deformity, determining the mechanical Lateral Distal Tibial Angle (mLDTA) is crucial. What is the generally accepted normal value for the mLDTA?

. 80 degrees
. 85 degrees
. 89 degrees
. 93 degrees
. 98 degrees

Correct Answer & Explanation

. 89 degrees

Explanation

The normal mechanical Lateral Distal Tibial Angle (mLDTA) averages approximately 89 degrees (range 86 to 92 degrees).

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