(A) Extensor carpi ulnaris and flexor digitorum superficialis
(B) Flexor digitorum profundus and flexor carpi ulnaris
(C) Flexor digitorum superficialis and palmaris longus
(D) Flexor pollicis longus and flexor digitorum profundus
(E) Pronator teres and brachioradialis

The correct response is Option D.

An undiagnosed compartment syndrome poses the greatest risk to the flexor digitorum profundus and flexor pollicis longus muscles in the forearm. These muscles lie within the deepest compartments adjacent to bone and thus typically experience the greatest increases in interstitial pressure, leading first to ischemia and then to muscle necrosis.

In patients who develop severe contractures (involving all four fingers) resulting from undiagnosed compartment syndrome, the deep flexor muscles are most often involved as previously mentioned. The superficial flexors (flexor
and finally the superficial extensors (brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum communis, extensor carpi ulnaris). The characteristic deformity in these patients does not develop until weeks or months later and manifests as flexion of the elbow and wrist, pronation of the forearm, adduction and flexion of the thumb, and extension at the level of the metacarpophalangeal joint and flexion at the level of the interphalangeal joint with a claw-type deformity. These patients may also have a loss of sensation in the hand resulting from ischemic injury to the median and ulnar nerves.

References
1. Botte MJ, Gelberman RH. Compartment syndrome and Volkmann's contracture. In: Peimer CA, ed. Surgery of the Hand and Upper Extremity. New York, NY: McGraw-Hill; 1996;2:1539-1558.
2. Rowland SA. Fasciotomy: the treatment of compartment syndrome. In: Green DP, Hotchkiss RN, Pederson WC, eds. Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone, Inc; 1999;1:689-710.

A 35-year-old woman has pain in the medial elbow and numbness and tingling of the ring and little fingers. Her symptoms are exacerbated by flexing the elbow with the forearm in supination. The most likely cause of this patient's findings is nerve entrapment within which of the following structures?

(A) Arcade of Frohse
(B) Arcade of Struthers
(C) Lacertus fibrosis
(D) Leash of Henry
(E) Ligament of Struthers

The correct response is Option B.

This patient has cubital tunnel syndrome, or compression of the ulnar nerve at the level of the elbow. Characteristic findings include numbness in the dorsoulnar aspect of the hand, in the little finger, and in the ulnar aspect of the ring finger, as well as weakness of the ulnar extrinsic and intrinsic muscles. Although there are several potential sites of nerve entrapment, it is most likely to occur within the arcade of Struthers. This is a group of fascial bands from the medial intermuscular septum that can entrap the nerve, such as following anterior transposition. Another potential site of entrapment is the band of Osborne, which constricts the ulnar nerve as it passes through the cubital tunnel. Release of this band is critical during neuroplasty.

Entrapment of the deep branch of the radial nerve, or posterior interosseous nerve, can occur at the arcade of Frohse, which is a fascial band located along the supinator muscle in the forearm, or at the vascular leash of Henry, which is a sling of radial recurrent vessels that crosses the radial nerve.

The lacertus fibrosus, a dense sheet of aponeurotic fascia that extends from the biceps tendon to the flexor muscle mass, is a potential site of entrapment of the median nerve at the level of the elbow. This nerve can also become entrapped more proximally by the ligament of Struthers, which forms between the supracondylar humeral process and the medial epicondyle.

References
1. Kitay GS, Osterman AL. Compression neuropathies: ulnar. In: Peimer CA, ed. Surgery of the Hand and Upper Extremity. New York, NY: McGraw-Hill, Inc; 1996;2:1339-1362.
2. Szabo RM. Entrapment and compression neuropathies. In: Green DP, Hotchkiss RN, Pederson WC, eds. Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone, Inc; 1999;2:1404-1447.

A 34-year-old secretary has difficulty extending the middle and ring fingers of the right hand. On examination, there is weakness with extension of the wrist, fingers, and thumb. There is no sensory deficit. This patient's findings are most consistent with

(A) C7 nerve root lesion
(B) lateral epicondylitis
(C) posterior interosseous nerve syndrome
(D) radial tunnel syndrome
(E) Wartenberg's syndrome

The correct response is Option C.

This patient has findings consistent with posterior interosseous nerve syndrome, which is initially characterized by weakness and pain in the forearm in the absence of sensory loss. Other findings include weakness of extension of the metacarpophalangeal joints of the fingers and interphalangeal joint of the thumb, as well as weakness of thumb abduction and wrist extension. Because the innervation of the extensor carpi radialis longus tendon lies above the elbow and is thus not affected, the wrist often deviates radially.

A patient with a C7 nerve root lesion would have weakness in the radially innervated muscles (including the triceps), as well as weakness in the muscles with median nerve innervation, such as the pronator teres, flexor carpi radialis, flexor digitorum superficialis, and flexor pollicis longus.

Lateral epicondylitis is characterized by sharp pain at the epicondyle that is exacerbated with passive flexion of the wrist and fingers with the elbow in extension. Injection of a corticosteroid may produce relief. Although patients with lateral epicondylitis may have positive findings on middle finger testing, severe pain with passive stretch is more typical.

Radial tunnel syndrome involves compression of the radial nerve and results in chronic, aching pain in the area of the lateral humerus, elbow, extensor mass, and dorsal wrist. In addition, patients have tenderness over the mobile wad. Severe pain is elicited on middle finger testing. Weakness is not characteristic.

Wartenberg's syndrome, or radial sensory nerve entrapment, is characterized by pain and/or paresthesias over the dorsoradial aspect of the hand and wrist. Tinel's sign will be positive along the course of the nerve, and the patient will have paresthesias with the forearm in hyperpronation and the wrist in neutral. Because the motor branch of the radial nerve divides more proximally, weakness is not seen.

References
1. Hynes D, Peimer CA. Compression neuropathies: radial. In: Peimer CA, ed. Surgery of the Hand and Upper Extremity. New York, NY: McGraw-Hill, Inc; 1996;2:1291-1305.
2. Mackinnon SE, Dellon AL. Radial nerve entrapment in the proximal forearm and brachium. In: Surgery of the Peripheral Nerve. New York, NY: Thieme Medical Publishers, Inc; 1988:289-303.

A 50-year-old woman has paresthesias of the right thumb six hours after undergoing anatomic open reduction and rigid internal fixation of a fracture of the right distal radius. The pain, numbness, and weakness are worsening. Which of the following is the most appropriate next step in management?

(A) Application of ice and elevation of the extremity
(B) Semmes-Weinstein monofilament testing
(C) Open carpal tunnel release
(D) Release of Guyon's canal
(E) Surgical exploration of the fracture site

The correct response is Option C.

In this patient who has acute carpal tunnel syndrome, the most appropriate management is open release of the carpal tunnel. Acute carpal tunnel syndrome can occur following injury, infection, or hemorrhage. Although appropriate reduction and stabilization of the fracture should typically be followed by rehabilitation of the soft tissues and wrist joint, open decompression of the median nerve in the carpal canal is the only logical next step in a patient who has developed acute carpal tunnel syndrome. Limited exposure techniques are contraindicated in patients with fractures.

Although application of ice and elevation of the extremity are part of normal fracture management, this course would be inadequate in a patient who has acute compression of the median nerve. Semmes-Weinstein monofilament testing will provide objective evidence of median nerve pathology but will not relieve the pain, numbness, and weakness. Release of Guyon's canal is appropriate for those patients who require decompression of the ulnar nerve at the wrist. Surgical exploration is recommended for definitive management of fractures not associated with carpal tunnel syndrome or other complications, and may not even be necessary in patients with simple fractures.

References
1. Rettig ME, Raskin KB, Melone CP. Fractures of the distal radius. In: Lichtman DM, Alexander AH, eds. The Wrist and its Disorders. Philadelphia, Pa: WB Saunders Co; 1997:347-372.
2. Seitz WH Jr. Complications and problems in the management of distal radius fractures. Hand Clin. 1994;10:117-123.

A 24-year-old man has a 2.5-cm gap in the distal digital nerve of the dominant right index finger after cutting the finger while using a saw. Which of the following donor nerves is most appropriate for autografting?

(A) Dorsal branch of the ulnar nerve
(B) Medial antebrachial cutaneous nerve
(C) Superficial radial nerve
(D) Sural nerve
(E) Terminal branch of the posterior interosseus nerve

The correct response is Option E.

Selection of an appropriate nerve graft depends on the length, diameter, and function required from the graft. In addition, sensory loss at the donor site should not present a functional problem.

In this patient, the terminal branch of the posterior interosseous nerve will best match the required specifications for replacement of the severed digital nerve. The posterior interosseous nerve can be found deep to the extensor tendons at the level of the wrist. It lies in the floor of the fourth extensor compartment on the radial side, ulnar and deep to the extensor pollicis longus tendon and muscle. The terminal branch is frequently harvested for digital nerve defects because one fascicular strand can be transferred to replace a single digital fascicle. Because it is an articular branch of the nerve, there is no associated sensory deficit.

All of the other sources can be used for grafting but are inferior to the terminal branch of the posterior interosseous nerve for the replacement of a digital nerve. Although the dorsal branch of the ulnar nerve can provide approximately 15 cm of nerve for grafting, harvest of this branch is associated with numbness on the dorsoulnar aspect of the hand. Harvest of the lateral and medial antebrachial cutaneous nerves can be associated with significant donor site morbidity. This is a less favored site for grafting due to the large amount of interfascicular tissue surrounding the nerves. The superficial radial nerve provides an excellent source for graft material, with minimal epineural tissue and tightly packed fascicles, and is best used for nerve reconstruction in a patient with a pre-existing lesion of the high
and posterior to the lateral malleolus in the ankle and can provide as much as 40 cm of nerve for grafting.

References
1. Brushart TM. Nerve repair and grafting. In: Green DP, Hotchkiss RN, Pederson WC, eds. Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone, Inc; 1999;2:1381-1403.
2. Hentz VR, Rosen JM, Xiao SJ, et al. The nerve gap dilemma: a comparison of nerves repaired end to end under tension with nerve grafts in a primate model. J Hand Surg. 1993;18A:417-425.
3. Wyrick JD, Stern PJ. Secondary nerve reconstruction. Hand Clin. 1992;8:587-598.

A 42-year-old man has the acute onset of ischemia in the dominant right upper extremity after sustaining a myocardial infarction. The patient undergoes embolectomy followed by infusion of heparin; 24 hours later, he has pain, tenseness, and tingling of the affected extremity. On examination, he has severe pain with passive range of motion of the elbow, forearm, wrist, and hand. Pulses are weak.

Which of the following is the most appropriate next step in management?

(A) Application of a wrist extensor fixator
(B) Incision and drainage
(C) Median nerve decompression
(D) Fasciotomy
(E) Brachial palmar arch bypass

The correct response is Option D.

This patient has developed acute ischemia in the upper extremity, a finding most likely caused by the development of cardiac mural thrombi. Cardiac mural thrombi can result from myocardial infarction or atrial fibrillation and can subsequently embolize. Emboli may also develop from the superficial palmar arch or subclavian artery. Embolectomy and anticoagulant therapy are usually recommended. However, because he has had ischemia for more than 24 hours prior to reperfusion, his condition has most likely progressed to compartment syndrome; the findings of pain, tenseness, and tingling are consistent with this diagnosis. Delayed reperfusion can lead to the onset of compartment syndrome. Therefore, the most appropriate next step is to perform fasciotomy, or compartment release, to relieve the progressively worsening muscle necrosis.

References
1. Botte MJ, Gelberman RH. Compartment syndrome and Volkmann's contracture. In: Peimer CA, ed. Surgery of the Hand and Upper Extremity. New York, NY: McGraw-Hill, Inc; 1996;2:1539-1558.
2. Rowland SA. Fasciotomy: the treatment of compartment syndrome. In: Green DP, Hotchkiss RN, Pederson WC, eds. Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone, Inc; 1999;1:689-710.