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ABOS Orthopaedic Surgery Part II study materials
ABOS Orthopaedic Surgery Part II study resources

ABOS Orthopaedic Surgery Part II practice questions

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Question 1Adult Reconstruction

A 68-year-old patient undergoes primary total hip arthroplasty through a posterior approach. Which postoperative precaution is most appropriate to reduce the risk of dislocation?

  1. Avoid hip flexion beyond 90 degrees and adduction past midline Correct answer.
  2. Sleep only in the prone position for two weeks
  3. Maintain strict non-weight-bearing for six weeks
  4. Avoid active hip extension and external rotation

Explanation

Posterior-approach precautions restrict hip flexion beyond 90 degrees, adduction past midline, and internal rotation to protect posterior soft tissues until they heal. Extension and external rotation are the positions typically safe after a posterior approach. Weight-bearing status and sleeping position are unrelated to prosthetic stability.

Question 2Adult Reconstruction

Which finding on a knee radiograph is most characteristic of advanced osteoarthritis rather than rheumatoid arthritis?

  1. Marginal erosions with symmetric joint space narrowing
  2. Uniform joint space loss with periarticular osteopenia
  3. Diffuse cartilage loss with a large synovial effusion
  4. Asymmetric medial compartment narrowing with subchondral sclerosis and osteophytes Correct answer.

Explanation

Osteoarthritis produces focal, asymmetric load-bearing compartment narrowing with subchondral sclerosis, cysts, and marginal osteophytes. Rheumatoid arthritis causes symmetric narrowing with periarticular osteopenia and marginal erosions.

Question 3Adult Reconstruction

During a primary total knee arthroplasty, which step most directly determines the mechanical axis of the reconstructed limb?

  1. The choice of tourniquet inflation pressure
  2. The distal femoral resection angle and tibial resection perpendicular to the mechanical axis Correct answer.
  3. The amount of posterior femoral condylar osteophyte removal
  4. The thickness of the polyethylene insert

Explanation

Limb alignment is set by the coronal orientation of the femoral and tibial resections relative to the mechanical axis. Polyethylene thickness affects soft tissue tension and joint line height, not overall coronal axis.

Question 4Adult Reconstruction

A patient is scheduled for total hip arthroplasty and has a history of a prior ipsilateral pelvic fracture treated with hardware. Which preoperative step is most important for surgical planning?

  1. Obtaining a CT scan to assess bone stock and hardware position Correct answer.
  2. Routine screening for metal allergy
  3. Preoperative autologous blood donation
  4. Discontinuing all anticoagulants for ten days

Explanation

Prior pelvic hardware and altered anatomy can complicate acetabular preparation and cup fixation, so CT defines bone stock and hardware location. Metal allergy screening and blood conservation are adjuncts, not the key planning step in this scenario.

Question 5Adult Reconstruction

Which organism is most commonly responsible for early acute prosthetic joint infection after total knee arthroplasty?

  1. Staphylococcus aureus Correct answer.
  2. Bacteroides fragilis
  3. Mycobacterium tuberculosis
  4. Candida albicans

Explanation

Gram-positive cocci, especially Staphylococcus aureus and coagulase-negative staphylococci, account for most early prosthetic joint infections. Mycobacteria, anaerobes, and fungi are uncommon causes.

Question 6Adult Reconstruction

Which component of the DePuy ASR-type metal-on-metal hip articulation has been most implicated in adverse local tissue reactions?

  1. The trunnion corrosion at the head-neck junction Correct answer.
  2. The polymethylmethacrylate cement mantle
  3. The polyethylene liner
  4. The acetabular screws

Explanation

Adverse local tissue reactions in metal-on-metal hips arise from metal wear debris and corrosion, prominently at the modular head-neck taper. Polyethylene, screws, and cement are not the source of metal ion release.

Question 7Adult Reconstruction

A patient with end-stage ankle arthritis and a prior ipsilateral knee arthrodesis is being considered for treatment. Which factor most strongly favors ankle arthrodesis over total ankle arthroplasty?

  1. Young age with high functional demand
  2. Severe ipsilateral hindfoot deformity with poor bone stock Correct answer.
  3. Isolated medial ankle joint space narrowing
  4. Well-preserved ankle range of motion

Explanation

Severe deformity, poor bone stock, and high-demand or young patients are relative indications for arthrodesis because arthroplasty durability and alignment correction are limited. Preserved motion and isolated narrowing are not themselves contraindications to replacement.

Question 8Adult Reconstruction

A 72-year-old patient has a periprosthetic femoral fracture around a well-fixed total hip stem with a stable implant and adequate bone stock. According to the Vancouver classification, which type is this?

  1. Type A
  2. Type B1 Correct answer.
  3. Type B2
  4. Type C

Explanation

Vancouver B1 fractures occur around a well-fixed stem with adequate bone stock; B2 involves a loose stem with adequate bone, and B3 a loose stem with poor bone. Type A is trochanteric and type C is distal to the stem.

Question 9Adult Reconstruction

A patient develops a draining wound two weeks after total knee arthroplasty. Which management strategy is most appropriate for an acute postoperative infection with a well-fixed implant?

  1. Observation with serial dressing changes alone
  2. Debridement with polyethylene exchange and retention of the components Correct answer.
  3. Long-term oral antibiotics without surgery
  4. Immediate two-stage exchange arthroplasty

Explanation

Acute postoperative infection with a stable implant and healthy soft tissues is best treated with debridement, irrigation, modular component exchange, and antibiotics. Two-stage exchange is reserved for chronic or refractory infection.

Question 10Adult Reconstruction

Which factor most increases the risk of aseptic loosening of a cemented total knee tibial component?

  1. Tourniquet deflation before cement curing
  2. Use of a posterior-stabilized insert
  3. Adequate cement penetration into sclerotic bone
  4. Varus malalignment of the tibial component Correct answer.

Explanation

Coronal malalignment increases asymmetric loads and shear at the bone-cement interface, promoting loosening. Good cement penetration improves fixation, and insert design does not itself cause loosening.

Question 11Adult Reconstruction

During a revision total hip arthroplasty, a patient has a Paprosky type IIIB acetabular defect. Which reconstruction strategy is most appropriate?

  1. Cemented all-polyethylene cup without augmentation
  2. Trabecular metal augment with a hemispherical cup and screws Correct answer.
  3. Impaction bone grafting with a cemented cup and no augments
  4. Press-fit hemispherical cup with screws alone

Explanation

Paprosky IIIB defects have severe bone loss with loss of host bone contact, requiring structural augmentation such as trabecular metal augments plus a hemispherical cup with screws. Simple press-fit or cemented cups alone cannot achieve stable fixation.

Question 12Adult Reconstruction

A patient reports anterior knee pain and patellar crepitus several months after posterior-stabilized total knee arthroplasty. Which cause is most likely?

  1. Deep infection of the tibial component
  2. Patellar clunk from fibrous tissue at the superior pole of the patella Correct answer.
  3. Aseptic loosening of the femoral component
  4. Periprosthetic fracture of the tibial tubercle

Explanation

Patellar clunk syndrome results from fibrous nodule formation at the superior pole of the patella catching on the femoral box in posterior-stabilized designs. It presents with crepitus and anterior pain during extension.

Question 13Adult Reconstruction

Which component is most commonly affected by polyethylene wear and osteolysis after total hip arthroplasty with a metal-on-polyethylene bearing?

  1. The femoral head
  2. The femoral stem
  3. The acetabular cup liner Correct answer.
  4. The acetabular screws

Explanation

Polyethylene wear debris from the acetabular liner drives macrophage-mediated osteolysis around the cup and femur. The metallic femoral head and stem are not the source of the wear particles.

Question 14Adult Reconstruction

A patient undergoes total hip arthroplasty and postoperatively develops foot drop with sensory loss over the dorsum of the foot. Which nerve is most likely injured?

  1. Sciatic nerve (peroneal division) Correct answer.
  2. Lateral femoral cutaneous nerve
  3. Obturator nerve
  4. Femoral nerve

Explanation

The peroneal division of the sciatic nerve is most vulnerable during total hip arthroplasty, producing foot drop and dorsal foot numbness. Femoral, obturator, and lateral femoral cutaneous injuries produce different deficits.

Question 15Adult Reconstruction

Which radiographic parameter is most useful for assessing acetabular component inclination after total hip arthroplasty?

  1. The angle between the cup face and the horizontal on an AP pelvis radiograph Correct answer.
  2. The distance from the teardrop to the cup center
  3. The femoral stem collar-to-tip length
  4. The greater trochanter tip-to-cup distance

Explanation

Inclination is measured as the angle between the acetabular cup face and the horizontal on an AP pelvis radiograph, typically targeting about 40 degrees. The other measurements do not assess cup orientation.

Question 16Adult Reconstruction

A patient with a well-functioning total knee arthroplasty presents with pain and swelling after a dental procedure. Which statement best reflects current evidence regarding antibiotic prophylaxis?

  1. Prophylaxis is recommended only within the first postoperative year
  2. Prophylaxis is recommended only for patients with metal-on-metal implants
  3. Prophylaxis is recommended for all dental procedures in all patients with arthroplasty
  4. Prophylaxis is not routinely recommended for patients with arthroplasty undergoing dental procedures Correct answer.

Explanation

Guidelines from orthopedic and dental societies do not support routine antibiotic prophylaxis before dental procedures for patients with joint replacements. The evidence for a link between dental bacteremia and prosthetic infection is weak.

Question 17Adult Reconstruction

Which factor most strongly predicts the need for revision after unicompartmental knee arthroplasty?

  1. Progression of arthritis in the unreplaced compartment Correct answer.
  2. Postoperative physical therapy duration
  3. Use of a fixed-bearing design
  4. Patient age under 60 years

Explanation

Progression of osteoarthritis in the contralateral compartment is a leading cause of failure and revision after unicompartmental knee arthroplasty. Age, bearing design, and therapy duration influence outcomes less directly.

Question 18Adult Reconstruction

A patient with a history of developmental dysplasia of the hip undergoes total hip arthroplasty. Which technical consideration is most important?

  1. The true acetabulum is often shallow and requires medialization and bone grafting Correct answer.
  2. The femoral neck should be lengthened to restore leg length in all cases
  3. The acetabular component should be placed in extreme anteversion
  4. A large femoral head is contraindicated

Explanation

In dysplastic hips the true acetabulum is shallow and superiorly deficient, so restoring the hip center often requires medialization, reaming to host bone, and structural grafting. Extreme component positions or indiscriminate lengthening risk instability and nerve injury.

Question 19Adult Reconstruction

A patient with a chronically infected total knee arthroplasty and a sinus tract undergoes two-stage exchange. Which interval management is most appropriate?

  1. A static antibiotic-loaded cement spacer left in place
  2. Retention of the original components with oral suppressive antibiotics
  3. An articulating antibiotic-loaded cement spacer with systemic antibiotics Correct answer.
  4. Immediate reimplantation without antibiotics

Explanation

An articulating antibiotic-loaded spacer maintains soft tissue tension and function while delivering local antibiotics during the interval before reimplantation. Static spacers are an alternative but increase stiffness; original components should be removed in chronic infection with a sinus tract.

Question 20Adult Reconstruction

Which biomechanical principle best explains why a highly cross-linked polyethylene liner reduces wear after total hip arthroplasty?

  1. Increased cross-linking eliminates the need for a femoral head
  2. Increased cross-linking decreases the melting temperature of the liner
  3. Increased cross-linking increases the coefficient of friction against the femoral head
  4. Increased cross-linking reduces multidirectional wear while oxidation is minimized Correct answer.

Explanation

Cross-linking reduces wear, particularly in multidirectional motion, and modern annealing or remelting steps limit oxidation and fatigue resistance loss. Friction, melting behavior, and the need for a femoral head are not the mechanism.

Question 21Adult Reconstruction

A patient with a periprosthetic joint infection is being evaluated for debridement with implant retention. Which factor most strongly reduces the likelihood of success?

  1. Symptoms present for less than three weeks
  2. Infection caused by a methicillin-sensitive organism
  3. A sinus tract communicating with the joint Correct answer.
  4. A well-fixed implant with a stable soft tissue envelope

Explanation

A sinus tract communicating with the joint indicates chronic infection and is a strong predictor of failure of debridement with implant retention. Short symptom duration, a stable implant, and a susceptible organism favor success.

Question 22Adult Reconstruction

Which factor most affects the long-term survival of a cemented femoral stem in total hip arthroplasty?

  1. The color of the polyethylene liner
  2. The use of a posterior surgical approach
  3. The quality of the cement mantle and stem alignment Correct answer.
  4. The number of acetabular screws

Explanation

Adequate cement mantle thickness and neutral stem alignment reduce interface stresses and improve long-term fixation. Liner color, screw number, and surgical approach do not determine cemented stem survival.

Question 23Basic Science

Which collagen type predominates in hyaline articular cartilage and forms the fibrillar network that resists tensile loading?

  1. Type II Correct answer.
  2. Type I
  3. Type III
  4. Type X

Explanation

Hyaline articular cartilage is built principally on a type II collagen framework that entraps proteoglycans and resists tensile stress. Type I dominates bone, tendon, and fibrocartilage, while type X marks hypertrophic chondrocytes in the growth plate.

Question 24Basic Science

A 62-year-old woman sustains a low-energy distal radius fracture. Which finding on her metabolic workup most specifically supports a diagnosis of primary hyperparathyroidism rather than postmenopausal osteoporosis?

  1. Normal serum calcium with low parathyroid hormone
  2. Low serum 25-hydroxyvitamin D
  3. Elevated serum calcium with elevated parathyroid hormone Correct answer.
  4. Low serum calcium with elevated alkaline phosphatase

Explanation

Primary hyperparathyroidism produces hypercalcemia with inappropriately elevated or high-normal PTH, reflecting autonomous gland function. Postmenopausal osteoporosis typically shows normal calcium and PTH, so the paired calcium-PTH pattern is the discriminator.

Question 25Basic Science

During intramembranous ossification, which process directly produces woven bone in a developing flat bone such as the calvaria?

  1. Enzymatic resorption of a calcified cartilage core
  2. Endochondral replacement of a cartilage template
  3. Direct differentiation of mesenchymal cells into osteoblasts Correct answer.
  4. Chondrocyte hypertrophy followed by vascular invasion

Explanation

Intramembranous ossification proceeds by direct conversion of condensed mesenchyme into osteoblasts that deposit osteoid without a cartilage intermediate. The other choices describe steps of endochondral ossification, which uses a cartilage model.

Question 26Basic Science

A peripheral nerve is subjected to a compressive force. According to the pressure threshold concept, which change is most likely to occur first as intraneural pressure rises?

  1. Axonal transection at the compression site
  2. Impaired venous outflow with edema Correct answer.
  3. Complete loss of motor conduction
  4. Arterial occlusion with ischemic necrosis

Explanation

Low-pressure compression first compromises the low-pressure venous and lymphatic outflow, producing intraneural edema before arterial supply is affected. Higher pressures are required to impair arterial inflow and ultimately conduction or axonal continuity.

Question 27Basic Science

In a normal mature bone remodeling cycle, which sequence correctly describes the coupled events at a basic multicellular unit?

  1. Simultaneous balanced resorption and formation with no temporal sequence
  2. Osteocyte-mediated resorption followed by chondrocyte-mediated formation
  3. Osteoblast-mediated formation followed by osteoclast-mediated resorption
  4. Osteoclast-mediated resorption followed by osteoblast-mediated formation Correct answer.

Explanation

Bone remodeling begins with osteoclastic resorption of a cavity, which is then refilled by osteoblasts recruited through coupling signals. This resorption-then-formation sequence is the basis of the remodeling cycle.

Question 28Basic Science

A researcher measures the stress-strain behavior of cortical bone loaded along its long axis versus transversely. Which statement best explains the observed anisotropy?

  1. Cortical bone is strongest in shear regardless of loading direction
  2. Cortical bone is isotropic because mineral content dominates its mechanical behavior
  3. Cortical bone behaves identically in tension and compression at all orientations
  4. Cortical bone is stronger and stiffer along its long axis owing to osteonal orientation Correct answer.

Explanation

Cortical bone is anisotropic, with osteons and collagen fibers aligned longitudinally, making it stiffer and stronger in the axial direction than transversely. Mineral content contributes to stiffness but does not abolish directional dependence.

Question 29Foot and Ankle

A 24-year-old basketball player sustains an inversion injury to the ankle. On examination there is tenderness over the lateral malleolus and the anterior talofibular ligament. Which ligament is most commonly the first to be injured in this injury pattern?

  1. Deltoid ligament
  2. Anterior talofibular ligament Correct answer.
  3. Calcaneofibular ligament
  4. Posterior talofibular ligament

Explanation

In inversion ankle sprains the lateral ligament complex fails in a predictable sequence, with the anterior talofibular ligament injured first, followed by the calcaneofibular ligament and, less commonly, the posterior talofibular ligament. The deltoid is a medial structure injured with eversion or external rotation.

Question 30Foot and Ankle

Which tendon passes through the fibro-osseous tunnel behind the medial malleolus and is most commonly implicated in posterior tibial tendon dysfunction?

  1. Flexor digitorum longus
  2. Posterior tibial tendon Correct answer.
  3. Flexor hallucis longus
  4. Tibialis anterior tendon

Explanation

Posterior tibial tendon dysfunction is the most common cause of adult acquired flatfoot, and the tendon courses behind the medial malleolus in its own fibro-osseous tunnel. The flexor hallucis longus and flexor digitorum longus share the tarsal tunnel but are not the primary lesion in this condition.

Question 31Foot and Ankle

A patient has a painful first metatarsophalangeal joint with a hallux valgus deformity. Which radiographic measurement describes the angle between the first and second metatarsal shafts?

  1. First metatarsophalangeal joint congruence angle
  2. Intermetatarsal angle Correct answer.
  3. Hallux valgus angle
  4. Distal metatarsal articular angle

Explanation

The intermetatarsal angle is measured between the longitudinal axes of the first and second metatarsals and is a key determinant of surgical planning in hallux valgus. The hallux valgus angle measures the first metatarsal to proximal phalanx relationship, and the distal metatarsal articular angle measures the orientation of the distal articular surface.

Question 32Foot and Ankle

A 45-year-old runner reports plantar heel pain that is worst with the first steps in the morning. Which diagnosis is most consistent with this presentation?

  1. Calcaneal stress fracture
  2. Tarsal tunnel syndrome
  3. Plantar fasciitis Correct answer.
  4. Achilles tendinopathy

Explanation

Plantar fasciitis classically produces medial heel pain that is most severe with the first steps after rest, reflecting the characteristic start-up pain. Achilles tendinopathy causes posterior heel pain, and tarsal tunnel syndrome produces neuropathic symptoms in the plantar foot.

Question 33Foot and Ankle

Which nerve is most commonly entrapped in the tarsal tunnel?

  1. Saphenous nerve
  2. Sural nerve
  3. Superficial peroneal nerve
  4. Tibial nerve Correct answer.

Explanation

Tarsal tunnel syndrome results from compression of the tibial nerve or its branches as they pass beneath the flexor retinaculum behind the medial malleolus. The sural, superficial peroneal, and saphenous nerves are located elsewhere and are not tarsal tunnel contents.

Question 34Foot and Ankle

A 62-year-old with diabetes presents with a deep, malodorous plantar ulcer over the first metatarsal head and probing reaches bone. What is the most appropriate next step in management?

  1. Plain radiographs and MRI to evaluate for osteomyelitis Correct answer.
  2. Total contact casting with weekly debridement
  3. Immediate below-knee amputation
  4. Topical antibiotic ointment and offloading shoes

Explanation

A deep plantar ulcer with exposed bone in a diabetic patient raises concern for osteomyelitis, and imaging with radiographs and MRI is required to assess bone involvement before definitive treatment. Offloading and local wound care remain important but do not replace evaluation for deep infection.

Question 35Foot and Ankle

A 30-year-old sustains an axial load injury to the midfoot with swelling and inability to bear weight. Which physical examination maneuver best assesses the Lisfranc ligament complex?

  1. Dorsoplantar squeeze of the midfoot Correct answer.
  2. Pronation-external rotation stress of the foot
  3. Single-leg heel raise
  4. Anterior drawer of the ankle

Explanation

The midfoot squeeze test applies compression across the tarsometatarsal joints and elicits pain when the Lisfranc complex is injured. Ankle drawer tests the lateral ligaments, and the single-leg heel raise assesses posterior tibial tendon function.

Question 36Foot and Ankle

A 55-year-old with a rigid flatfoot and severe valgus hindfoot deformity has failed conservative treatment. Which procedure is most appropriate?

  1. Isolated gastrocnemius recession
  2. Isolated medial displacement calcaneal osteotomy
  3. Ankle arthroscopy
  4. Triple arthrodesis Correct answer.

Explanation

Rigid, severe stage flatfoot deformity with a fixed valgus hindfoot generally requires arthrodesis, and triple arthrodesis addresses the subtalar, talonavicular, and calcaneocuboid joints. Isolated osteotomy or tendon procedures are appropriate only for flexible deformities.

Question 37Foot and Ankle

A patient has an acute Achilles tendon rupture with a palpable gap and a positive Thompson test. Which finding defines a positive Thompson test?

  1. Pain on passive dorsiflexion of the ankle
  2. Plantar flexion of the foot with calf squeeze
  3. Absence of plantar flexion with calf squeeze Correct answer.
  4. Dorsiflexion of the foot with calf squeeze

Explanation

The Thompson test squeezes the calf; with an intact Achilles tendon this produces plantar flexion, whereas a complete rupture abolishes that response. Pain with passive dorsiflexion is nonspecific and does not define the test.

Question 38Foot and Ankle

A 14-year-old presents with activity-related heel pain and radiographs show increased density and fragmentation of the calcaneal apophysis. What is the most appropriate initial management?

  1. Open reduction and internal fixation
  2. Corticosteroid injection into the apophysis
  3. Activity modification, heel cushioning, and stretching Correct answer.
  4. Immediate cast immobilization for six weeks

Explanation

Calcaneal apophysitis (Sever disease) is a self-limited traction apophysitis treated with activity modification, heel cups, and stretching of the calf and hamstrings. Surgery, injections, and prolonged casting are not indicated for this benign condition.

Question 39Foot and Ankle

A 35-year-old has a Morton neuroma between the third and fourth metatarsal heads. Which finding is most characteristic on examination?

  1. Weakness of ankle dorsiflexion
  2. A positive Mulder click with a plantar-directed squeeze Correct answer.
  3. A positive Tinel sign at the medial malleolus
  4. Tenderness over the first metatarsophalangeal joint

Explanation

A Morton neuroma of the third web space produces a palpable or audible click as the intermetatarsal ligament is squeezed and the neuroma displaces plantarly. Medial malleolar Tinel sign and ankle dorsiflexion weakness suggest other diagnoses.

Question 40Foot and Ankle

A 28-year-old has recurrent lateral ankle instability after failing a structured rehabilitation program. Which procedure is most commonly performed?

  1. Syndesmotic screw fixation
  2. Deltoid ligament repair
  3. Brostrom-Gould lateral ligament reconstruction Correct answer.
  4. Posterior tibial tendon transfer

Explanation

The Brostrom-Gould anatomic repair, often augmented with the inferior extensor retinaculum, is the standard operative treatment for chronic lateral ankle instability after failed nonoperative care. The deltoid and syndesmosis are not the primary structures addressed in lateral instability.

Question 41Foot and Ankle

A 68-year-old with a Charcot midfoot and a rocker-bottom deformity has a stable, braceable foot with no ulceration. What is the most appropriate initial management?

  1. Serial casting for six months
  2. Immediate arthrodesis of the midfoot
  3. Below-knee amputation
  4. Custom accommodative bracing and protective footwear Correct answer.

Explanation

In a stable Charcot foot without ulceration, accommodative bracing and protective footwear are the mainstay of treatment to prevent ulceration and further deformity. Surgery is reserved for instability, recurrent ulceration, or failure of bracing.

Question 42Foot and Ankle

A 40-year-old sustains a twisting injury with pain over the lateral foot. Radiographs show a Jones fracture. Which anatomic region does this fracture involve?

  1. Tuberosity of the fifth metatarsal
  2. Distal fifth metatarsal neck
  3. Proximal diaphysis of the fifth metatarsal at the metaphyseal-diaphyseal junction Correct answer.
  4. First metatarsal base

Explanation

A Jones fracture occurs at the metaphyseal-diaphyseal junction of the fifth metatarsal, distal to the tuberosity and within a watershed vascular zone, which explains its higher nonunion rate. Tuberosity avulsions are more proximal and generally heal more reliably.

Question 43Foot and Ankle

A patient has a chronic, displaced talar neck fracture with avascular necrosis of the talar body. Which blood supply is most important for talar body perfusion?

  1. Anterior tibial artery branches to the talar head
  2. Artery of the tarsal canal from the posterior tibial artery Correct answer.
  3. Perforating branches of the peroneal artery
  4. Dorsalis pedis artery only

Explanation

The artery of the tarsal canal, a branch of the posterior tibial artery, is the dominant supply to the talar body, and disruption of this supply in displaced talar neck fractures predisposes to avascular necrosis. Other vessels provide supplemental flow but are not the primary supply.

Question 44Foot and Ankle

A 22-year-old presents with a chronic, painful flatfoot and a rigid hindfoot. Imaging reveals a tarsal coalition. Which coalition is most common?

  1. Calcaneonavicular coalition Correct answer.
  2. Talonavicular coalition
  3. Subtalar coalition between the posterior facet and calcaneus
  4. Calcaneocuboid coalition

Explanation

Calcaneonavicular coalition is the most common tarsal coalition, followed by talocalcaneal coalition. Coalitions restrict subtalar motion and produce a rigid flatfoot, often presenting in adolescence.

Question 45Hand and Microvascular

A patient sustains a closed mallet finger injury with inability to actively extend the distal interphalangeal joint but no fracture on radiographs. What is the most appropriate initial management?

  1. Volar plate release of the DIP joint
  2. Buddy taping to the proximal interphalangeal joint
  3. Continuous DIP extension splinting for 6 to 8 weeks Correct answer.
  4. Immediate surgical repair of the terminal extensor tendon

Explanation

Tendinous mallet finger without fracture is treated nonoperatively with continuous DIP extension splinting, typically for 6 to 8 weeks, allowing the terminal tendon to heal. Surgery is reserved for cases with large avulsion fragments, subluxation, or failed conservative care.

Question 46Hand and Microvascular

Which nerve is most commonly compressed in the carpal tunnel?

  1. Radial sensory nerve
  2. Median nerve Correct answer.
  3. Ulnar nerve
  4. Posterior interosseous nerve

Explanation

Carpal tunnel syndrome results from compression of the median nerve as it passes beneath the transverse carpal ligament. The ulnar nerve travels through Guyon's canal, not the carpal tunnel.

Question 47Hand and Microvascular

A patient has a laceration over the volar aspect of the index finger with loss of flexion at the PIP joint but intact DIP flexion. Which structure is most likely injured?

  1. Flexor digitorum profundus tendon
  2. Extensor central slip
  3. Flexor digitorum superficialis tendon Correct answer.
  4. A2 pulley

Explanation

The flexor digitorum superficialis inserts on the middle phalanx and is responsible for PIP flexion, while the profundus flexes the DIP. Isolated loss of PIP flexion with intact DIP flexion indicates superficialis injury.

Question 48Hand and Microvascular

What is the most common site of a true digital artery aneurysm in the hand?

  1. Common digital artery of the ring finger
  2. Proper digital artery of the thumb ulnar side Correct answer.
  3. Princeps pollicis artery
  4. Superficial palmar arch

Explanation

Hypothenar hammer syndrome affects the ulnar artery, but true digital artery aneurysms most often involve the proper digital arteries of the fingers, particularly the ulnar digital artery of the thumb. These are often related to repetitive trauma.

Question 49Hand and Microvascular

A patient presents with a Dupuytren contracture affecting the metacarpophalangeal joint of the small finger to 40 degrees. Which treatment is most appropriate for isolated MCP joint contracture?

  1. Percutaneous needle fasciotomy Correct answer.
  2. Proximal interphalangeal joint arthrodesis
  3. Radial forearm free flap
  4. Extensor tendon tenolysis

Explanation

Isolated MCP joint contractures in Dupuytren disease respond well to percutaneous needle fasciotomy or collagenase injection, with good correction and low morbidity. Surgical fasciectomy is reserved for more extensive or recurrent disease.

Question 50Hand and Microvascular

Which test is most specific for diagnosing a scaphoid fracture when initial radiographs are negative but clinical suspicion remains high?

  1. Phalen test
  2. Tinel sign at the wrist
  3. MRI of the wrist Correct answer.
  4. Watson scaphoid shift test

Explanation

MRI has high sensitivity and specificity for occult scaphoid fractures and can detect other injuries such as ligamentous disruption. The Watson test assesses scapholunate instability, not fracture.