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 781
Topic: Nerve & Tendon
A rugby player sustains a flexor digitorum profundus (FDP) avulsion from the ring finger (Jersey finger). MRI confirms the tendon has retracted completely into the palm (Leddy-Packer Type 1). What is the optimal timeframe for surgical repair?
Correct Answer & Explanation
. Within 7-10 days
Explanation
Type 1 Jersey fingers involve retraction of the FDP into the palm, which ruptures the vincular blood supply. Repair must be performed within 7-10 days before the tendon undergoes necrosis and irreversible contracture.
Question 782
Topic: Nerve & Tendon
A 22-year-old rugby player grabs an opponent's jersey and sustains an isolated hyperextension injury to his ring finger distal interphalangeal (DIP) joint. Imaging demonstrates an avulsed bony fragment located at the level of the proximal interphalangeal (PIP) joint. What Leddy-Packer type is this injury, and what is its vincular status?
Correct Answer & Explanation
. Type II; preserved vincula longa
Explanation
This is a Type II jersey finger, where the FDP tendon retracts to the level of the PIP joint and is arrested by the intact vincula longa. Because some blood supply is preserved, repair can often be safely delayed for up to a few weeks, unlike Type I injuries.
Question 783
Topic: Nerve & Tendon
A 45-year-old woman presents with a chronic, untreated mallet finger of the middle digit. She has progressively developed a severe swan neck deformity. What is the primary pathomechanical cause of this secondary deformity?
Correct Answer & Explanation
. Proximal retraction of the extensor mechanism concentrating force on the central slip
Explanation
Chronic disruption of the terminal tendon allows the entire extensor mechanism to migrate proximally. This migration concentrates the extensor forces entirely onto the central slip, causing secondary hyperextension of the PIP joint and a swan neck deformity.
Question 784
Topic: Nerve & Tendon
A patient presents with a deep forearm laceration. On physical examination, they are completely unable to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger (unable to make an 'OK' sign). Which of the following nerve branches and corresponding muscles are paralyzed?
Correct Answer & Explanation
. Recurrent motor branch of median nerve: Opponens pollicis, Abductor pollicis brevis
Explanation
The inability to make the 'OK' sign implies loss of flexion at the IP joint of the thumb and DIP joint of the index finger. These movements are controlled by the Flexor Pollicis Longus (FPL) and the radial half of the Flexor Digitorum Profundus (FDP), both innervated by the Anterior Interosseous Nerve (AIN).
Question 785
Topic: Nerve & Tendon
A 40-year-old man undergoes an electromyography (EMG) study for a suspected nerve entrapment. The neurologist notes the presence of a Martin-Gruber anastomosis. What does this anatomic variant typically represent?
Correct Answer & Explanation
. Motor branches from the median nerve cross to the ulnar nerve in the forearm.
Explanation
The Martin-Gruber anastomosis is a common anomalous connection in the forearm where motor fibers from the median nerve (or anterior interosseous nerve) cross over to join the ulnar nerve. This can result in atypical EMG findings and spared intrinsic hand function in proximal ulnar nerve injuries.
Question 786
Topic: Nerve & Tendon
During the volar (Russe) approach to the scaphoid for open reduction and internal fixation of a waist fracture, the surgical interval for deep exposure involves incising the sheath of which of the following tendons?
Correct Answer & Explanation
. Flexor pollicis longus
Explanation
The volar approach to the scaphoid requires an incision centered over the flexor carpi radialis (FCR) tendon. The FCR tendon sheath is opened, and the tendon is retracted ulnarly (to protect the median nerve) or radially (to protect the radial artery). The deep floor of the FCR sheath is incised to access the volar radiocarpal capsule and the scaphoid.
Question 787
Topic: Nerve & Tendon
A patient with an isolated nerve injury is unable to actively flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger, resulting in a positive "OK" sign. Which of the following muscles is ALSO innervated by the affected nerve?
Correct Answer & Explanation
. Flexor carpi radialis
Explanation
The patient has an anterior interosseous nerve (AIN) palsy. The AIN is a pure motor branch of the median nerve that innervates the flexor pollicis longus, the flexor digitorum profundus to the index and middle fingers, and the pronator quadratus.
Question 788
Topic: Nerve & Tendon
The recurrent motor branch of the median nerve (the "million dollar nerve") innervates the thenar musculature. Which of the following muscles is primarily innervated by the deep branch of the ulnar nerve rather than the median nerve?
Correct Answer & Explanation
. Opponens pollicis
Explanation
The adductor pollicis and the deep head of the flexor pollicis brevis are innervated by the deep branch of the ulnar nerve. The median nerve supplies the LOAF muscles: Lumbricals 1 & 2, Opponens pollicis, Abductor pollicis brevis, and the superficial head of the Flexor pollicis brevis.
Question 789
Topic: Nerve & Tendon
A patient develops an inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger following a forearm injury. Sensation is completely intact. Which of the following structures is most likely causing compression of the involved nerve?
Correct Answer & Explanation
. Arcade of Frohse
Explanation
This presentation describes anterior interosseous nerve (AIN) syndrome, characterized by pure motor loss to the FPL, FDP (index/middle), and pronator quadratus. The AIN is most commonly compressed by the tendinous edge of the deep head of the pronator teres or the fibrous arch of the FDS.
Question 790
Topic: Nerve & Tendon
A 4-year-old child sustains a mildly displaced (<2mm) lateral condyle fracture of the humerus, which is treated non-operatively in a long arm cast. Three months later, radiographs reveal a frank nonunion of the lateral condyle. If left untreated, what late neurological complication is most characteristic of this condition?
Correct Answer & Explanation
. Tardy ulnar nerve palsy
Explanation
Nonunion of a lateral condyle fracture typically results in progressive cubitus valgus deformity. Over time, the valgus deformity progressively stretches the ulnar nerve behind the medial epicondyle, leading to a delayed neuropathy known as 'tardy ulnar nerve palsy', which can present years or even decades after the initial injury.
Question 791
Topic: Nerve & Tendon
A 5-year-old child sustains a minimally displaced (<2 mm) lateral condyle fracture of the humerus. If left completely untreated and progressing to a nonunion, what is the most likely long-term complication?
Correct Answer & Explanation
. Cubitus valgus and tardy ulnar nerve palsy
Explanation
A nonunion of a lateral condyle fracture leads to progressive superior migration of the lateral condyle, resulting in a progressive cubitus valgus deformity. Over time, this stretches the ulnar nerve, classically leading to a tardy ulnar nerve palsy.
Question 792
Topic: Nerve & Tendon
A 55-year-old female with long-standing rheumatoid arthritis presents with a finger deformity characterized by PIP joint hyperextension and DIP joint flexion.
What is the primary pathophysiologic event initiating this specific deformity?
Correct Answer & Explanation
. Attenuation of the central slip
Explanation
Swan neck deformity is characterized by PIP hyperextension and DIP flexion. In RA, it often initiates from synovitis leading to volar plate laxity and PIP hyperextension, with secondary DIP flexion. Conversely, Boutonniere deformity starts with attenuation of the central slip, leading to volar subluxation of the lateral bands.
Question 793
Topic: Nerve & Tendon
A cyclist complains of numbness in his small finger and the ulnar half of his ring finger, along with intrinsic muscle weakness.
Which of the following zones of Guyon's canal is most likely compressed if the patient presents with purely motor symptoms (weakness of hypothenar and interossei muscles) with NO sensory deficits?
Correct Answer & Explanation
. Zone 1
Explanation
Guyon's canal is divided into three zones. Zone 1 is proximal to the bifurcation and compression causes mixed motor and sensory symptoms. Zone 2 is the deep motor branch, and compression causes pure motor symptoms (weakness of intrinsic muscles). Zone 3 is the superficial sensory branch, and compression causes pure sensory symptoms to the ulnar digits.
Question 794
Topic: Nerve & Tendon
A 40-year-old female presents with severe, lancinating pain in her fingertip, exquisitely sensitive to cold. Examination reveals a bluish discoloration beneath the nail matrix.
Which of the following clinical tests is most specific for diagnosing this condition?
Correct Answer & Explanation
. Tinel's sign
Explanation
The clinical presentation is classic for a glomus tumor. Hildreth's test is performed by inflating a tourniquet on the proximal arm or digit, which relieves the pain of a glomus tumor due to cessation of blood flow. This test has high specificity. Love's pin test (exquisite point tenderness using a pinhead) and the cold sensitivity test are also characteristic.
Question 795
Topic: Nerve & Tendon
A patient complains of numbness in the small finger. On examination, there is weakness of the flexor digitorum profundus to the small finger (FDP) and a positive Froment's sign.
This presentation indicates ulnar nerve compression at what level?
Correct Answer & Explanation
. Guyon's canal
Explanation
Weakness of the FDP to the small finger indicates that the ulnar nerve compression is proximal to the wrist, typically at the elbow (cubital tunnel syndrome). The motor branches to the FDP and FCU take off in the proximal forearm. Compression at Guyon's canal (wrist) spares the FDP and FCU, presenting with intrinsic muscle weakness (positive Froment's sign) but normal FDP function.
Question 796
Topic: Nerve & Tendon
A 22-year-old rugby player grabbed an opponent's jersey and felt a pop in his ring finger. He cannot actively flex the distal interphalangeal (DIP) joint. Radiographs reveal a small bony fragment retracted to the level of the proximal interphalangeal (PIP) joint. According to the Leddy and Packer classification, what type of injury is this, and what is its blood supply status?
Correct Answer & Explanation
. Type II, supported by the intact long vinculum, requires repair within a few weeks
Explanation
Jersey finger is an avulsion of the flexor digitorum profundus (FDP) tendon. In the Leddy and Packer classification: Type I retracts to the palm, rupturing both vincula (requires early repair within 7-10 days to prevent contracture and necrosis). Type II retracts to the level of the PIP joint, caught by the intact long vinculum (preserves some blood supply, can be repaired slightly later). Type III is a large bony avulsion caught at the A4 pulley. Type IV is a bony avulsion with simultaneous avulsion of the tendon off the bony fragment.
Question 797
Topic: Nerve & Tendon
A 35-year-old male sustains a high ulnar nerve transection above the elbow. After primary repair, the surgeon decides to perform a distal supercharged nerve transfer to rapidly restore intrinsic hand function before irreversible muscle atrophy occurs. Which of the following nerve transfers is most commonly used for this purpose?
Correct Answer & Explanation
. Anterior interosseous nerve to the deep motor branch of the ulnar nerve
Explanation
For high ulnar nerve injuries, distal nerve transfers are employed to bypass the long regeneration distance. The transfer of the terminal branch of the anterior interosseous nerve (AIN) (which supplies the pronator quadratus) to the deep motor branch of the ulnar nerve is the most established technique to rapidly reinnervate the intrinsic muscles of the hand.
Question 798
Topic: Nerve & Tendon
A 42-year-old female presents with severe, paroxysmal pain in her left index fingertip that is exquisitely sensitive to cold temperatures. Examination reveals a bluish hue and pinpoint tenderness beneath the nail plate. Which of the following clinical tests is most specific for diagnosing the suspected lesion?
Correct Answer & Explanation
. Finkelstein test
Explanation
The clinical picture is classic for a Glomus tumor (pain, cold sensitivity, pinpoint tenderness). Hildreth's test involves inducing transient ischemia of the digit with a tourniquet; if the pinpoint pain disappears during ischemia and returns upon release, the test is positive. It is highly specific for a glomus tumor.
Question 799
Topic: Nerve & Tendon
A patient presents with a finger deformity characterized by PIP joint flexion and DIP joint hyperextension. What is the primary anatomic defect responsible for this deformity?
Correct Answer & Explanation
. Rupture of the terminal extensor tendon
Explanation
A Boutonniere deformity is caused by the attenuation or rupture of the central slip of the extensor apparatus at the PIP joint. This allows the lateral bands to subluxate volarly and become flexors of the PIP and extensors of the DIP.
Question 800
Topic: Nerve & Tendon
A 32-year-old cyclist presents with weakness in his hand after a long-distance race. Examination reveals weak finger abduction and adduction, and a positive Froment's sign. Sensation over the entire little finger and the ulnar half of the ring finger is completely normal. In which zone of Guyon's canal is the compression most likely located?
Correct Answer & Explanation
. Zone 1
Explanation
Zone 2 of Guyon's canal contains only the deep motor branch of the ulnar nerve. Compression here (e.g., from a ganglion cyst or hook of hamate fracture) causes isolated motor weakness of the ulnar-innervated intrinsics with spared sensation.
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