This practice set contains high-yield board review questions covering key concepts in 7. Hand and Wrist. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.
Question 2801
Topic: 7. Hand and Wrist
The deep palmar arch of the hand provides significant collateral blood flow. It is primarily formed by the anastomosis of which of the following vessels?
Correct Answer & Explanation
. Superficial branch of the radial artery and terminal ulnar artery
Explanation
The deep palmar arch is primarily formed by the terminal portion of the radial artery anastomosing with the deep branch of the ulnar artery. The superficial palmar arch is primarily formed by the terminal ulnar artery.
Question 2802
Topic: 7. Hand and Wrist
When utilizing a dorsal approach to the wrist, Lister's tubercle is a key osseous landmark. It serves as a mechanical pulley for which tendon?
Correct Answer & Explanation
. Extensor carpi radialis longus
Explanation
Lister's tubercle (dorsal tubercle of the radius) separates the second and third extensor compartments. The extensor pollicis longus (EPL) tendon uses this tubercle as a pulley to change its line of pull toward the thumb.
Question 2803
Topic: Nerve & Tendon
A 6-year-old boy presents with an extension-type supracondylar humerus fracture. Radiographs demonstrate posterolateral displacement of the distal fragment. Which of the following neurologic structures is at greatest risk of injury?
Correct Answer & Explanation
. Anterior interosseous nerve
Explanation
Posterolateral displacement of the distal fragment in an extension-type supracondylar humerus fracture tethers the anterior/medial structures, placing the anterior interosseous nerve (AIN) at greatest risk. Posteromedial displacement places the radial nerve at risk.
Question 2804
Topic: Nerve & Tendon
A 6-year-old girl falls from monkey bars and sustains a displaced extension-type supracondylar humerus fracture with posteromedial displacement of the distal fragment. Which nerve is most commonly injured in this specific fracture pattern?
Correct Answer & Explanation
. Ulnar nerve
Explanation
Posteromedial displacement of the distal fragment in an extension-type supracondylar humerus fracture puts the radial nerve at the greatest risk of stretch or entrapment over the proximal fragment.
Question 2805
Topic: Nerve & Tendon
A 7-year-old girl falls directly onto a flexed elbow. Radiographs reveal a flexion-type supracondylar humerus fracture. Which of the following nerve injuries is most strongly associated with this specific fracture pattern?
Correct Answer & Explanation
. Anterior interosseous nerve
Explanation
While the anterior interosseous nerve is most commonly injured in extension-type fractures, flexion-type supracondylar humerus fractures are uniquely associated with a higher incidence of ulnar nerve injury due to the nerve's posterior position.
Question 2806
Topic: 7. Hand and Wrist
A 6-year-old boy falls on an outstretched hand and sustains a widely displaced extension-type supracondylar humerus fracture. On examination, he is unable to actively flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Which of the following nerves is most likely injured?
Correct Answer & Explanation
. Radial nerve
Explanation
The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type supracondylar humerus fractures. Injury presents with the inability to make an "OK" sign due to weakness of the flexor pollicis longus and flexor digitorum profundus to the index finger. Most AIN palsies in this setting are neuropraxias that resolve with observation.
Question 2807
Topic: Nerve & Tendon
A 7-year-old boy sustains a flexion-type supracondylar fracture of the humerus after falling onto a flexed elbow. Radiographs show anterior displacement of the distal fracture fragment. Which nerve is most commonly injured in this specific fracture pattern?
Correct Answer & Explanation
. Anterior interosseous nerve
Explanation
Flexion-type supracondylar humerus fractures account for approximately 2-5% of cases and involve anterior displacement of the distal fragment. They are uniquely associated with a higher incidence of ulnar nerve injury, unlike extension types which typically injure the anterior interosseous nerve.
Question 2808
Topic: Nerve & Tendon
A 5-year-old girl falls from monkey bars and sustains a displaced extension-type supracondylar humerus fracture. Examination reveals she is unable to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Which nerve is most likely injured?
Correct Answer & Explanation
. Ulnar nerve
Explanation
The anterior interosseous nerve (AIN), a branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. Injury presents as the inability to make an "OK" sign due to loss of FPL and FDP function to the index finger.
Question 2809
Topic: Wrist & Carpus
A 9-year-old boy undergoes closed reduction and casting for a midshaft both-bone forearm fracture. During healing, he develops an angular malunion. Loss of which of the following anatomic features is most likely to significantly restrict his functional supination and pronation?
Correct Answer & Explanation
. The normal dorsal tilt of the distal radius
Explanation
The native lateral bow of the radius is critical for allowing the radius to rotate around the ulna during supination and pronation. Angular deformities that flatten or reverse the radial bow cause profound deficits in forearm rotation.
Question 2810
Topic: Nerve & Tendon
A 5-year-old boy sustained a pediatric lateral condyle fracture of the distal humerus 2 years ago, which was treated non-operatively. He now presents with progressive cubitus valgus. Which of the following tardy nerve palsies is most likely to develop?
Correct Answer & Explanation
. Median nerve
Explanation
Nonunion of a lateral condyle fracture can lead to progressive cubitus valgus. This deformity stretches the ulnar nerve behind the medial epicondyle, classically leading to tardy ulnar nerve palsy.
Question 2811
Topic: Nerve & Tendon
A 5-year-old child sustains a widely displaced (3 mm) lateral condyle fracture of the humerus. If left untreated and a nonunion develops, which of the following complications is most likely to present years later?
Correct Answer & Explanation
. Median nerve palsy
Explanation
Untreated displaced lateral condyle fractures have a high rate of nonunion, which frequently leads to a progressive cubitus valgus deformity. The resulting valgus stretch over time can stretch the ulnar nerve, producing a classic tardy ulnar nerve palsy.
Question 2812
Topic: Nerve & Tendon
A 7-year-old boy sustains an extension-type supracondylar humerus fracture. Neurologic examination reveals an inability to actively flex the interphalangeal joint of his thumb and the distal interphalangeal joint of his index finger. Which nerve is most likely injured?
Correct Answer & Explanation
. Ulnar nerve
Explanation
The anterior interosseous nerve (AIN), a branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. It provides motor innervation to the flexor pollicis longus and the flexor digitorum profundus to the index and middle fingers.
Question 2813
Topic: Nerve & Tendon
A 5-year-old boy presents with a lateral condyle fracture of the distal humerus displaced by 4 mm. If this fracture is managed nonoperatively in a cast, what is the most likely long-term complication?
Correct Answer & Explanation
. Cubitus varus and median nerve palsy
Explanation
Displaced lateral condyle fractures treated nonoperatively have a high rate of nonunion. This nonunion can lead to a progressive cubitus valgus deformity, which stretches the ulnar nerve and causes tardy ulnar nerve palsy.
Question 2814
Topic: Nerve & Tendon
A 10-year-old boy presents with an elbow dislocation and an associated displaced fracture of the medial epicondyle of the humerus. Which nerve is most commonly injured in association with this specific injury pattern?
Correct Answer & Explanation
. Radial nerve
Explanation
The ulnar nerve passes directly posterior to the medial epicondyle in the cubital tunnel. It is highly susceptible to traction or direct impingement in medial epicondyle fractures and elbow dislocations.
Question 2815
Topic: Nerve & Tendon
A 5-year-old girl sustains a displaced lateral condyle fracture of the distal humerus. If left untreated and progressing to nonunion, which of the following is the most likely long-term complication?
Correct Answer & Explanation
. Cubitus varus and tardy ulnar nerve palsy
Explanation
Nonunion of a pediatric lateral condyle fracture typically leads to a progressive cubitus valgus deformity due to the proximal migration of the un-united lateral fragment. Over time, this valgus deformity stretches the ulnar nerve, resulting in a tardy ulnar nerve palsy.
Question 2816
Topic: 7. Hand and Wrist
A 6-year-old girl is diagnosed with congenital scoliosis due to a fully segmented unilateral hemivertebra at T8. Which of the following imaging studies is most critical to obtain during her initial workup?
Correct Answer & Explanation
. MRI of the brain
Explanation
Congenital scoliosis is frequently associated with other VACTERL anomalies. Up to 30% of patients have genitourinary abnormalities, making a screening renal ultrasound critical in the initial evaluation.
Question 2817
Topic: 7. Hand and Wrist
What is the biomechanical rationale for advising a patient with severe left hip osteoarthritis to hold a cane in their right hand?
Correct Answer & Explanation
. It increases the necessary abductor muscle force
Explanation
Using a cane in the contralateral hand creates an upward force that generates a torque opposing the body weight. This significantly reduces the necessary force output by the ipsilateral hip abductors, which in turn drastically lowers the total joint reaction force on the affected hip.
Question 2818
Topic: 7. Hand and Wrist
A 7-year-old boy falls on an outstretched hand and sustains a plastic deformation fracture of the proximal ulna with an associated radial head dislocation. Which nerve is most commonly injured in this specific fracture-dislocation pattern?
Correct Answer & Explanation
. Median nerve
Explanation
This injury pattern is a Monteggia fracture-dislocation. The posterior interosseous nerve (PIN), a deep branch of the radial nerve, wraps around the radial neck and is the most frequently injured nerve during radial head dislocation.
Question 2819
Topic: Wrist & Carpus
In a Galeazzi fracture-dislocation, which of the following stabilizing structures is most commonly disrupted, leading to instability of the distal radioulnar joint (DRUJ)?
Correct Answer & Explanation
. Radial collateral ligament
Explanation
A Galeazzi fracture involves a fracture of the distal third of the radial shaft with associated disruption of the DRUJ. The Triangular Fibrocartilage Complex (TFCC) is the primary stabilizer of the DRUJ and is typically torn or avulsed in this injury pattern.
Question 2820
Topic: Wrist & Carpus
A 55-year-old woman sustained a nondisplaced distal radius fracture treated in a short arm cast. Two weeks after the cast was removed (6 weeks post-injury), she notes a sudden inability to actively extend the interphalangeal joint of her thumb. Radiographs confirm the distal radius fracture is healing well in anatomic alignment. What is the most appropriate surgical treatment?
Correct Answer & Explanation
. Direct end-to-end repair of the extensor pollicis longus (EPL) tendon
Explanation
Delayed rupture of the EPL tendon occurs due to mechanical attrition or ischemia at Lister's tubercle, especially in nondisplaced distal radius fractures. Because the tendon ends are typically retracted and degenerated, direct repair is usually impossible, making an EIP to EPL transfer the gold standard.
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