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8. Foot and Ankle MCQs

Practice Set 337 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 6721

Topic: Midfoot & Hindfoot

A 64-year-old male with diabetes and loss of protective sensation develops Charcot arthropathy. Which of the following anatomic locations is most commonly affected by neuropathic arthropathy in the diabetic foot?

. Ankle joint
. Subtalar joint
. Tarsometatarsal (Lisfranc) joint
. Metatarsophalangeal joints
. Talonavicular joint

Correct Answer & Explanation

. Tarsometatarsal (Lisfranc) joint

Explanation

Correct Answer: CThe tarsometatarsal (Lisfranc) joint complex is the most common site of Charcot arthropathy in the diabetic foot, accounting for approximately 60% of cases. This is classified as Brodsky Type 1. Collapse at this level leads to the classic 'rocker-bottom' foot deformity, where the midfoot collapses plantarward, creating a new, abnormal pressure point that is highly susceptible to ulceration. Brodsky Type 2 involves the hindfoot (subtalar/Chopart joints), and Type 3 involves the ankle joint.

Question 6722

Topic: 8. Foot and Ankle

A 68-year-old male with diabetes presents with a Wagner Grade 1 neuropathic ulcer under the first metatarsal head. He has palpable pedal pulses and an ABI of 1.1. He has no signs of systemic infection. What is the gold standard treatment for healing this ulcer?

. Split-thickness skin grafting
. Total contact casting
. First metatarsophalangeal joint arthrodesis
. Hyperbaric oxygen therapy
. Daily wet-to-dry dressings

Correct Answer & Explanation

. Total contact casting

Explanation

Correct Answer: BFor a non-infected, non-ischemic plantar neuropathic ulcer (Wagner Grade 1 or 2), the gold standard for offloading and promoting healing is the total contact cast (TCC). The TCC works by redistributing plantar pressures over the entire surface area of the foot and lower leg, significantly reducing focal pressure at the ulcer site. It also forces patient compliance with offloading. Surgery is reserved for ulcers that fail conservative management or are associated with deep infection/osteomyelitis.

Question 6723

Topic: 8. Foot and Ankle

A 50-year-old male with long-standing diabetes presents with a warm, swollen, and erythematous right foot. Radiographs demonstrate early fragmentation of the naviculocuneiform joint. During rounds, the attending physician discusses the pathogenesis of this condition, specifically highlighting the neurovascular theory. Which of the following mechanisms best describes this theory?

. Ischemic necrosis of bone due to microvascular disease
. Autonomic neuropathy leading to arteriovenous shunting and active bone resorption
. Venous stasis leading to periosteal reaction and bone hypertrophy
. Motor neuropathy causing abnormal mechanical stress on joints
. Glycosylation of collagen leading to brittle bones

Correct Answer & Explanation

. Autonomic neuropathy leading to arteriovenous shunting and active bone resorption

Explanation

Correct Answer: BThere are two primary theories for the pathogenesis of Charcot arthropathy. The neurotraumatic theory postulates that loss of protective sensation allows repetitive microtrauma to destroy the joint. The neurovascular theory postulates that autonomic neuropathy leads to a loss of sympathetic tone, causing arteriovenous shunting and increased blood flow (hyperemia) to the foot. This hyperemia stimulates osteoclastic activity, leading to active bone resorption, osteopenia, and subsequent mechanical failure (fracture/fragmentation) of the weakened bone.

Question 6724

Topic: 8. Foot and Ankle

A third-year medical student is instructed to perform a diabetic foot screening on a 66-year-old female using a 5.07 Semmes-Weinstein monofilament. Which of the following describes the most appropriate technique for administering this test?

. Drag the monofilament across the plantar skin to assess for dynamic touch
. Apply the monofilament perpendicular to the skin until it buckles, hold for 1-2 seconds, and release
. Apply the monofilament with rapid, repetitive taps over the metatarsal heads
. Apply the monofilament specifically to areas of thick plantar callus to assess deep pressure
. Apply the monofilament parallel to the skin surface to assess light touch

Correct Answer & Explanation

. Apply the monofilament perpendicular to the skin until it buckles, hold for 1-2 seconds, and release

Explanation

Correct Answer: BThe correct technique for using the Semmes-Weinstein monofilament is to apply it perpendicular to the skin surface until it buckles, hold it for approximately 1 to 2 seconds, and then release. The buckling ensures that exactly 10 grams of force is applied. It should not be dragged or tapped. Furthermore, it should be applied to normal skin and specifically avoid areas of thick callus, scars, or necrotic tissue, as these areas have naturally altered sensation and will yield false-positive results for neuropathy.

Question 6725

Topic: Midfoot & Hindfoot

According to the Brodsky classification of Charcot arthropathy, which anatomical area is involved in the most common pattern (Type 1)?

. Chopart joint
. Tarsometatarsal (Lisfranc) and naviculocuneiform joints
. Subtalar joint
. Ankle joint
. Posterior calcaneal tuberosity

Correct Answer & Explanation

. Tarsometatarsal (Lisfranc) and naviculocuneiform joints

Explanation

Brodsky Type 1 involves the tarsometatarsal (Lisfranc) and naviculocuneiform joints, comprising roughly 60% of cases. It is the most common pattern and frequently leads to midfoot collapse and a classic "rocker-bottom" deformity.

Question 6726

Topic: 8. Foot and Ankle

A 55-year-old diabetic patient is placed in a Total Contact Cast (TCC) for a plantar neuropathic ulcer. What is the primary biomechanical mechanism by which the TCC facilitates ulcer healing?

. Immobilizing the ankle to eliminate the calf muscle pump
. Transferring 80% of weight-bearing forces directly to the patellar tendon
. Increasing arterial perfusion via localized thermal retention
. Redistributing plantar pressures over a larger surface area, including the longitudinal arch
. Promoting controlled shear stress to stimulate granulation tissue formation

Correct Answer & Explanation

. Redistributing plantar pressures over a larger surface area, including the longitudinal arch

Explanation

A TCC works by redistributing weight-bearing forces evenly over the entire surface area of the foot, especially the non-weight-bearing longitudinal arch. This significantly reduces focal peak plantar pressure at the ulcer site, allowing the tissue to heal.

Question 6727

Topic: 8. Foot and Ankle

A 65-year-old diabetic male requires an amputation for a non-reconstructable Charcot foot with intractable ulceration. Which of the following transcutaneous oxygen tension (TcPO2) values indicates the accepted minimum threshold for a high probability of wound healing?

. > 10 mmHg
. > 20 mmHg
. > 30 mmHg
. > 40 mmHg
. > 50 mmHg

Correct Answer & Explanation

. > 30 mmHg

Explanation

A TcPO2 of > 30 mmHg is the widely accepted minimum threshold for predictable wound healing in lower extremity amputations. Values < 20 mmHg are associated with consistent wound failure and require a higher level of amputation or revascularization.

Question 6728

Topic: 8. Foot and Ankle
A 50-year-old diabetic patient presents with a stable, Eichenholtz Stage III Charcot midfoot and a fixed rocker-bottom deformity. He has a recurrent plantar ulcer over a bony prominence despite strict use of a CROW boot. There is no evidence of osteomyelitis. What is the most appropriate next step in management?
. Intravenous antibiotics for 6 weeks
. Midfoot exostectomy
. Transtibial amputation
. Extensive midfoot arthrodesis
. Repeated Total Contact Casting indefinitely

Correct Answer & Explanation

. Midfoot exostectomy

Explanation

In a stable, burned-out (Stage III) Charcot foot with a localized bony prominence causing a recalcitrant ulcer, an exostectomy is the procedure of choice. Arthrodesis is generally reserved for unstable deformities or when conservative bracing fails to maintain alignment.

Question 6729

Topic: 8. Foot and Ankle

Prophylactic Achilles tendon lengthening (TAL) is often performed in conjunction with diabetic forefoot ulcer management. What is the primary biomechanical rationale for this adjunctive procedure?

. It restores normal ankle dorsiflexion power
. It decreases plantar forefoot and midfoot pressures during the terminal stance phase of gait
. It prevents the development of hindfoot valgus
. It increases blood flow to the posterior tibial artery by reducing compartmental pressure
. It actively corrects an associated cavovarus deformity

Correct Answer & Explanation

. It decreases plantar forefoot and midfoot pressures during the terminal stance phase of gait

Explanation

Equinus contracture is common in diabetics due to non-enzymatic glycosylation of the Achilles tendon. TAL decreases peak plantar forefoot and midfoot pressures during the terminal stance phase, significantly reducing the risk of recurrent ulceration.

Question 6730

Topic: 8. Foot and Ankle

A diabetic patient with severe bilateral Charcot arthropathy undergoes a unilateral Syme amputation. Compared to a baseline normal human gait, what is the expected increase in energy expenditure for ambulation?

. 10-15%
. 25-30%
. 40-50%
. 60-75%
. Greater than 100%

Correct Answer & Explanation

. 10-15%

Explanation

A Syme (ankle disarticulation) amputation increases energy expenditure by roughly 15% due to the preservation of a long lever arm and potential for end-bearing. In contrast, a vascular transtibial amputation increases it by 40%, and a vascular transfemoral by up to 100%.

Question 6731

Topic: 8. Foot and Ankle

A diabetic patient presents with a unilaterally warm, swollen, and erythematous foot. Radiographs are normal. The erythema completely resolves after 10 minutes of limb elevation. What is the most likely diagnosis and initial management?

. Cellulitis treated with IV antibiotics
. Deep vein thrombosis treated with systemic anticoagulation
. Eichenholtz Stage 0 Charcot treated with Total Contact Casting
. Eichenholtz Stage I Charcot treated with early open reduction and internal fixation
. Gout treated with oral indomethacin

Correct Answer & Explanation

. Eichenholtz Stage 0 Charcot treated with Total Contact Casting

Explanation

Erythema that resolves with elevation (dependent rubor) differentiates Charcot from infection. A warm, swollen foot with normal radiographs indicates Eichenholtz Stage 0 (acute inflammatory) Charcot, which requires immediate offloading via TCC to prevent progressive deformity.

Question 6732

Topic: 8. Foot and Ankle

Brodsky Type 3 Charcot neuroarthropathy involves the ankle joint. Which of the following statements regarding this specific pattern is most accurate?

. It is the most common anatomic type of Charcot arthropathy
. It is typically managed successfully with custom shoe inserts alone
. It is highly unstable and often requires early tibio-talo-calcaneal (TTC) arthrodesis
. It rarely leads to significant bone loss or severe deformity
. It is exclusively caused by neurovascular changes without any neurotraumatic component

Correct Answer & Explanation

. It is highly unstable and often requires early tibio-talo-calcaneal (TTC) arthrodesis

Explanation

Brodsky Type 3 involves the ankle and/or subtalar joint. It is notorious for being highly unstable, rapidly progressive, and difficult to control with bracing alone, frequently necessitating early tibiotalocalcaneal (TTC) arthrodesis to prevent amputation.

Question 6733

Topic: 8. Foot and Ankle
A diabetic patient with a chronic foot ulcer undergoes vascular testing. The Ankle-Brachial Index (ABI) is measured at 1.4. What is the most accurate clinical interpretation of this value?
. Normal arterial flow with excellent wound healing potential
. Mild peripheral arterial disease requiring antiplatelet therapy
. Severe limb-threatening ischemia requiring immediate bypass
. Non-compressible calcified vessels resulting in a falsely elevated reading
. Severe venous insufficiency masquerading as arterial disease

Correct Answer & Explanation

. Non-compressible calcified vessels resulting in a falsely elevated reading

Explanation

An ABI > 1.3 indicates non-compressible, calcified tibial vessels (Mรถnckeberg's arteriosclerosis), a common finding in long-standing diabetes. This renders the ABI unreliable, necessitating alternative measures like the Toe-Brachial Index (TBI) or TcPO2.

Question 6734

Topic: 8. Foot and Ankle

Diabetic neuropathy often leads to the development of claw toe deformities, increasing the risk of dorsal and plantar ulcerations. What is the primary neuromuscular pathogenesis of this specific deformity?

. Spasticity of the extensor digitorum longus
. Atrophy and paralysis of the intrinsic foot musculature (lumbricals and interossei)
. Isolated contracture of the central slip of the plantar fascia
. Weakness of the flexor digitorum longus
. Hyperactivity of the tibialis posterior

Correct Answer & Explanation

. Atrophy and paralysis of the intrinsic foot musculature (lumbricals and interossei)

Explanation

Motor neuropathy in diabetes leads to atrophy of the intrinsic foot muscles. The intact extrinsic extensors then overpower the weak intrinsics, leading to metatarsophalangeal joint extension and interphalangeal joint flexion (claw toes).

Question 6735

Topic: Midfoot & Hindfoot
Which of the following radiographic features represents the hallmark of Eichenholtz Stage I Charcot neuroarthropathy?
. Coalescence of major fracture fragments and absorption of fine debris
. Subchondral sclerosis with prominent osteophyte formation
. Bone marrow edema on MRI without any cortical breaks on X-ray
. Active bone fragmentation, joint subluxation, and periarticular debris
. Complete, stable bony ankylosis of the midfoot joints

Correct Answer & Explanation

. Active bone fragmentation, joint subluxation, and periarticular debris

Explanation

Eichenholtz Stage I (Development/Fragmentation) is characterized by active bone fragmentation, joint subluxation or dislocation, periarticular debris, and joint space widening. Stage II features coalescence, and Stage III features reconstruction/consolidation.

Question 6736

Topic: Midfoot & Hindfoot

A 52-year-old diabetic female has profound, unbraceable midfoot instability from acute Charcot arthropathy (Eichenholtz Stage I) with severe edema. What is the modern consensus regarding surgical arthrodesis at this specific stage?

. It is the gold standard for all patients to prevent eventual bone loss
. It is absolutely contraindicated under any circumstances due to infection risk
. It is historically avoided, but can be considered if severe unbraceable instability threatens the soft tissue envelope
. It requires a mandatory two-stage approach with an initial external fixator for 6 months
. It is best managed with soft tissue releases (TAL) alone, avoiding all bone work

Correct Answer & Explanation

. It is historically avoided, but can be considered if severe unbraceable instability threatens the soft tissue envelope

Explanation

Historically, surgery was absolutely contraindicated in Eichenholtz Stage I due to poor bone quality and high failure rates. Modern consensus, however, allows for surgical stabilization in Stage I if the deformity is severe, unbraceable, and threatens to cause an impending ulceration.

Question 6737

Topic: 8. Foot and Ankle

Preoperative nutritional assessment is critical before undertaking reconstructive surgery for a diabetic Charcot foot. Which of the following laboratory values strongly suggests an increased risk of postoperative wound complications and infection?

. Total lymphocyte count of 2500/mm^3
. Serum albumin < 3.0 g/dL
. HbA1c of 6.5%
. Hemoglobin of 13.5 g/dL
. Serum prealbumin of 25 mg/dL

Correct Answer & Explanation

. Serum albumin < 3.0 g/dL

Explanation

A serum albumin level < 3.0 g/dL (or prealbumin < 15 mg/dL) indicates significant malnutrition. This is a recognized major risk factor for poor wound healing, dehiscence, and postoperative infection in orthopedic foot and ankle surgery.

Question 6738

Topic: 8. Foot and Ankle

A 60-year-old diabetic patient presents with a Charcot arthropathy of the foot. Radiographs demonstrate collapse and fragmentation at the tarsometatarsal and naviculocuneiform joints. According to the Brodsky classification, which type of Charcot arthropathy does this represent?

. Type 1
. Type 2
. Type 3A
. Type 3B
. Type 4

Correct Answer & Explanation

. Type 1

Explanation

Brodsky Type 1 involves the midfoot (tarsometatarsal and naviculocuneiform joints) and is the most common anatomical pattern in Charcot arthropathy. Type 2 involves the hindfoot, and Type 3 involves the ankle or calcaneus.

Question 6739

Topic: 8. Foot and Ankle

A 55-year-old diabetic male with an uninfected plantar ulcer presents with a swollen, warm foot. MRI shows diffuse marrow edema in the midfoot. Which imaging modality is most specific for differentiating acute Charcot arthropathy from superimposed osteomyelitis?

. Three-phase technetium-99m bone scan
. Gallium-67 scan
. Indium-111 WBC scan combined with Tc-99m sulfur colloid marrow scan
. Non-contrast MRI
. CT scan of the foot

Correct Answer & Explanation

. Indium-111 WBC scan combined with Tc-99m sulfur colloid marrow scan

Explanation

The combination of an Indium-111 WBC scan with a Tc-99m sulfur colloid marrow scan is highly specific for distinguishing osteomyelitis from Charcot neuroarthropathy. It accurately differentiates true infection from the inflammatory marrow changes seen in acute Charcot.

Question 6740

Topic: 8. Foot and Ankle

Total contact casting (TCC) is considered the gold standard for offloading in diabetic foot ulcers and acute Charcot arthropathy. Which of the following is an absolute contraindication to the application of a TCC?

. Superficial Wagner Grade 1 ulcer
. Palpable pedal pulses
. Active deep foot infection with abscess
. History of prior toe amputation
. Eichenholtz stage 1 Charcot with edema

Correct Answer & Explanation

. Active deep foot infection with abscess

Explanation

Absolute contraindications to TCC include active deep infection (abscess, osteomyelitis, gangrene), severe peripheral arterial disease, and deep unmapped fistulas. TCC in the presence of an active abscess can lead to rapidly progressive, limb-threatening infection.

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