This practice set contains high-yield board review questions covering key concepts in Nerve & Tendon. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.
Question 1021
Topic: Nerve & Tendon
A 6-year-old boy sustains a completely displaced extension-type supracondylar fracture of the humerus. Radiographs demonstrate posteromedial displacement of the distal fragment. Which of the following peripheral nerves is at the highest risk of tethering or injury due to the sharply displaced proximal fragment?
Correct Answer & Explanation
. Radial nerve
Explanation
In an extension-type supracondylar humerus fracture with posteromedial displacement of the distal fragment, the proximal fragment naturally displaces anterolaterally. This anterolateral spike of bone places the radial nerve at the highest risk of injury.
Question 1022
Topic: Nerve & Tendon
Following a closed crush injury to the forearm, a patient suffers a median nerve palsy. If an exploratory nerve surgery were performed, it would reveal that the axons and their endoneurial tubes are completely disrupted, but the perineurium and epineurium remain perfectly intact. According to the Sunderland classification, this injury is a:
Correct Answer & Explanation
. Grade III
Explanation
Sunderland Grade III nerve injuries involve disruption of the axon and the endoneurium, while the perineurium and epineurium remain intact. Grade I is neurapraxia (focal demyelination). Grade II is axonotmesis with intact endoneurium. Grade IV involves disruption of the perineurium (only epineurium intact). Grade V is a complete nerve transection.
Question 1023
Topic: Nerve & Tendon
A 32-year-old male presents with a severely displaced diaphyseal fracture of the radius and ulna. During his neurological examination, he demonstrates an inability to actively flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Sensation is intact. Which nerve is most likely injured?
Correct Answer & Explanation
. Anterior interosseous nerve
Explanation
The anterior interosseous nerve (AIN), a pure motor branch of the median nerve, innervates the flexor pollicis longus (FPL), the flexor digitorum profundus (FDP) to the index and middle fingers, and the pronator quadratus. Injury results in the 'OK sign' deficit.
Question 1024
Topic: Nerve & Tendon
A competitive cyclist complains of profound weakness in finger abduction and adduction, along with a positive Froment's sign. He reports completely normal sensation in his ring and small fingers. Which zone of Guyon's canal is the most likely site of ulnar nerve compression?
Correct Answer & Explanation
. Zone 2
Explanation
Guyon's canal is divided into three zones. Zone 1 contains the main trunk of the ulnar nerve (compression causes both motor and sensory deficits). Zone 2 contains the deep motor branch (compression causes isolated motor deficits of the intrinsic muscles). Zone 3 contains the superficial sensory branch (compression causes isolated sensory deficits). The patient's isolated motor deficit localizes to Zone 2.
Question 1025
Topic: Nerve & Tendon
A patient with a severe ulnar nerve injury at the elbow demonstrates noticeably less severe clawing of the ring and small fingers compared to a patient with an ulnar nerve injury at the wrist. What anatomical mechanism explains this presentation (the Ulnar Paradox)?
Correct Answer & Explanation
. Paralysis of the ulnar half of the flexor digitorum profundus
Explanation
The Ulnar Paradox refers to the phenomenon where a high ulnar nerve injury produces less severe clawing because it denervates the ulnar half of the flexor digitorum profundus (FDP). Without active FDP contraction, the distal interphalangeal joints do not actively flex, reducing the visible claw deformity.
Question 1026
Topic: Nerve & Tendon
A heavy machinery worker sustains a deep volar laceration in "No Man's Land" of the hand, resulting in an inability to flex the proximal and distal interphalangeal joints. Which flexor tendon zone is anatomically involved?
Correct Answer & Explanation
. Zone II
Explanation
Zone II extends from the proximal edge of the A1 pulley to the insertion of the flexor digitorum superficialis (FDS). It is historically termed "No Man's Land" due to the tight fibro-osseous tunnel that makes surgical repair prone to adhesions and poor functional outcomes.
Question 1027
Topic: Nerve & Tendon
A 30-year-old male presents with inability to actively flex the distal interphalangeal joint of his ring finger after a rugby tackle. Radiographs and ultrasound show the flexor digitorum profundus (FDP) tendon retracted into the palm. According to the Leddy-Packer classification, what is the ideal timeframe for surgical repair of this specific injury pattern?
Correct Answer & Explanation
. Within 7 to 10 days
Explanation
A Type I FDP avulsion (Jersey finger) involves tendon retraction into the palm, disrupting its vincula and blood supply. It must be surgically repaired within 7 to 10 days to prevent permanent ischemic contracture of the tendon.
Question 1028
Topic: Nerve & Tendon
A 5-year-old boy is brought to the emergency department after falling from monkey bars. He sustained a completely displaced extension-type supracondylar humerus fracture. His hand is pink and well-perfused, but he is unable to make an "OK" sign with his thumb and index finger. Which of the following structures is most likely injured, and what is its typical anatomical course at the elbow?
Correct Answer & Explanation
. Anterior interosseous nerve; passes between the two heads of the pronator teres.
Explanation
Correct Answer: AThe inability to make an "OK" sign indicates an injury to the anterior interosseous nerve (AIN), which innervates the flexor pollicis longus and the flexor digitorum profundus to the index finger. AIN neuropraxia is the most common nerve injury associated with extension-type supracondylar humerus fractures. The AIN is a motor branch of the median nerve, which passes between the humeral and ulnar heads of the pronator teres muscle in the proximal forearm.
Question 1029
Topic: Nerve & Tendon
A 48-year-old construction worker presents with insidious onset of unilateral elbow pain and weakness, primarily affecting grip strength. He describes pain exacerbated by pronation and resisted wrist flexion. Tenderness is noted over the pronator teres muscle belly and the origin of the flexor carpi radialis. Compression of the median nerve in the proximal forearm reproduces symptoms. What is the most likely diagnosis?
Correct Answer & Explanation
. Pronator teres syndrome
Explanation
The symptoms of unilateral elbow pain, weakness, pain with pronation and resisted wrist flexion, tenderness over the pronator teres/flexor carpi radialis origin, and reproduction of symptoms with median nerve compression in the proximal forearm are highly suggestive of Pronator Teres Syndrome. This is a median nerve entrapment neuropathy in the proximal forearm, typically at the level of the pronator teres. Medial epicondylitis involves the common flexor origin but typically without neurological symptoms. Lateral epicondylitis involves the common extensor origin. Cubital tunnel syndrome is ulnar nerve entrapment at the elbow. Radial tunnel syndrome involves the posterior interosseous nerve (PIN), causing pain without motor weakness or sensory deficits initially.
Question 1030
Topic: Nerve & Tendon
What is the most critical anatomical structure to preserve during surgical repair of a mallet finger?
Correct Answer & Explanation
. Germinal matrix of the nail.
Explanation
During surgical repair of a mallet finger, which involves rupture or avulsion of the extensor tendon at the distal interphalangeal (DIP) joint, it is absolutely critical to preserve the germinal matrix of the nail. The germinal matrix is responsible for nail growth. Damage to this structure can result in permanent nail deformity, which is a significant functional and cosmetic complication. The flexor tendons are on the opposite side. The central slip is involved in PIP extension. The extensor digitorum communis is the tendon that ruptures, but its overall preservation is not as critical as the germinal matrix for post-op function and appearance.
Question 1031
Topic: Nerve & Tendon
A 40-year-old female undergoes a mini-open carpal tunnel release. Post-operatively, she complains of an inability to palmar abduct her thumb. Examination shows weakness of the abductor pollicis brevis, but normal sensation in the radial 3.5 digits. Which structure was most likely injured?
Correct Answer & Explanation
. Recurrent motor branch of the median nerve
Explanation
The recurrent motor branch of the median nerve innervates the abductor pollicis brevis, opponens pollicis, and the superficial head of the flexor pollicis brevis. Its injury results in loss of thumb palmar abduction without sensory deficits.
Question 1032
Topic: Nerve & Tendon
A 35-year-old male develops chronic, severe burning pain and allodynia in his forearm following a recognized median nerve injury from a glass laceration. What feature distinguishes his diagnosis of CRPS Type II from CRPS Type I?
Correct Answer & Explanation
. Presence of a definable peripheral nerve injury
Explanation
CRPS is divided into Type I (formerly Reflex Sympathetic Dystrophy) and Type II (formerly Causalgia). The defining difference is that Type II involves a verified, definable peripheral nerve injury.
Question 1033
Topic: Nerve & Tendon
During an open carpal tunnel release, the surgeon must be careful to avoid injury to the recurrent motor branch of the median nerve. Which of the following muscles is primarily innervated by this specific branch?
Correct Answer & Explanation
. Opponens pollicis
Explanation
Correct Answer: Opponens pollicisThe recurrent motor branch of the median nerve innervates the thenar muscles, which can be remembered by the mnemonic 'OAF': Opponens pollicis, Abductor pollicis brevis, and the superficial head of the Flexor pollicis brevis. The adductor pollicis and first dorsal interosseous are innervated by the deep branch of the ulnar nerve.
Question 1034
Topic: Nerve & Tendon
A 6-year-old boy sustains an extension-type supracondylar humerus fracture. He is unable to make an 'OK' sign with his thumb and index finger. Which nerve is most likely injured, and what is its typical course of recovery?
Correct Answer & Explanation
. Anterior interosseous nerve; typically recovers spontaneously within 2-3 months
Explanation
Correct Answer: Anterior interosseous nerve; typically recovers spontaneously within 2-3 monthsThe anterior interosseous nerve (AIN), a branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. It innervates the flexor pollicis longus and the flexor digitorum profundus to the index finger, which are required to make the 'OK' sign. These injuries are typically neuropraxias that resolve spontaneously within 2 to 3 months, and observation is the standard of care.
Question 1035
Topic: Nerve & Tendon
A 6-year-old boy sustains an extension-type supracondylar humerus fracture. On physical examination, he 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
. Anterior interosseous nerve
Explanation
Correct Answer: Anterior interosseous nerveThe anterior interosseous nerve (AIN), a motor branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. It innervates the flexor pollicis longus (FPL), the flexor digitorum profundus (FDP) to the index and middle fingers, and the pronator quadratus. Injury leads to the inability to make an 'OK' sign (loss of thumb IP and index DIP flexion). The radial nerve is the second most commonly injured, particularly with posteromedial displacement, while the ulnar nerve is more commonly injured in flexion-type fractures or iatrogenically during medial pin placement.
Question 1036
Topic: Nerve & Tendon
A 5-year-old boy sustained a lateral condyle fracture of the humerus that was treated nonoperatively. Two years later, he presents with a nonunion. Which of the following is the most common long-term neurological complication associated with this specific nonunion?
Correct Answer & Explanation
. Tardy ulnar nerve palsy
Explanation
Nonunion of a lateral condyle fracture typically results in a progressive cubitus valgus deformity. This progressive valgus stretch on the medial side of the elbow commonly leads to a tardy ulnar nerve palsy years later.
Question 1037
Topic: Nerve & Tendon
A 6-year-old boy falls from the monkey bars and sustains a completely displaced, extension-type supracondylar humerus fracture. Radiographs demonstrate posterolateral displacement of the distal fragment. Which nerve is most likely to be injured in this specific fracture pattern, and what is the classic clinical finding?
Correct Answer & Explanation
. Anterior interosseous nerve; inability to flex the IP joint of the thumb and DIP joint of the index finger
Explanation
Correct Answer: AIn extension-type supracondylar humerus fractures, the direction of displacement dictates the structures at risk. Posterolateral displacement of the distal fragment causes the sharp proximal fragment to displace anteromedially, putting the median nerve—specifically its anterior interosseous nerve (AIN) branch—and the brachial artery at greatest risk. AIN palsy is the most common nerve injury in extension-type supracondylar fractures overall. It is a purely motor nerve, and injury results in the inability to flex the interphalangeal (IP) joint of the thumb (flexor pollicis longus) and the distal interphalangeal (DIP) joint of the index finger (flexor digitorum profundus), leading to an abnormal 'A-OK' sign. Posteromedial displacement puts the radial nerve at risk. Flexion-type fractures put the ulnar nerve at risk.
Question 1038
Topic: Nerve & Tendon
A 5-year-old boy sustains a widely displaced extension-type supracondylar humerus fracture. On examination in the emergency department, he is unable to flex the interphalangeal joint of his thumb and the distal interphalangeal joint of his index finger. He has normal two-point discrimination over the palmar aspect of the hand. Which of the following structures is most likely injured, and what is the expected recovery pattern?
Correct Answer & Explanation
. B) Anterior interosseous nerve; typically resolves spontaneously within 3-6 months
Explanation
Correct Answer: BThe patient exhibits a classic "OK sign" deficit, indicating an inability to flex the flexor pollicis longus (FPL) and the flexor digitorum profundus (FDP) to the index finger. This is the hallmark of an anterior interosseous nerve (AIN) palsy. The AIN is a purely motor branch of the median nerve, which aligns with the patient's normal sensation in the hand. AIN injury is the most common neurologic deficit associated with extension-type supracondylar humerus fractures (often due to traction or contusion over the proximal fracture fragment). The vast majority of these injuries are neuropraxias that resolve spontaneously. Observation for 3 to 6 months is the standard of care. Immediate exploration (Option A) is not indicated for isolated, closed nerve injuries in this setting. The median nerve proper (Options C and D) would present with sensory deficits in the palmar thumb, index, and middle fingers. Ulnar nerve injuries (Option E) are more commonly associated with flexion-type supracondylar fractures or iatrogenic injury from medial pin placement.
Question 1039
Topic: Nerve & Tendon
A 6-year-old boy sustained a lateral condyle humerus fracture that was treated nonoperatively with 4 mm of displacement. He now presents 2 years later with a symptomatic nonunion. Which of the following deformities and late nerve palsies are most commonly associated with this complication?
Correct Answer & Explanation
. Cubitus valgus and ulnar nerve palsy
Explanation
Nonunion of lateral condyle humerus fractures typically leads to a progressive cubitus valgus deformity. Over time, the valgus alignment stretches the ulnar nerve, resulting in a tardy ulnar nerve palsy.
Question 1040
Topic: Nerve & Tendon
A 45-year-old female presents with a deep intramuscular lipoma in the proximal anterior forearm near the supinator muscle. She reports insidious, progressive weakness in extending her thumb and fingers, without any sensory deficits. Which nerve is most likely compressed by this mass?
Correct Answer & Explanation
. Posterior interosseous nerve
Explanation
A mass near the supinator muscle (arcade of Frohse) can compress the posterior interosseous nerve (PIN). PIN compression results in motor weakness of thumb and finger extensors, without sensory loss (as the sensory component travels via the superficial radial nerve).
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