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The hand is innervated by the median, ulnar, and radial nerves. Motor function of the median nerve can be screened by flexing the thumb distal phalanx against resistance, the ulnar nerve by spreading the fingers against resistance, and the radial nerve by maintaining extension of the wrist and fingers against resistance. Sensory innervation (Fig. 170-1) is best screened by the presence of normal 2-point discrimination (<6 mm). Injuries requiring hand surgery consultation are listed in Tables 170-1 and 170-2.
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Tendon injuries can be missed if one does not know and examines the hand in the position it was in at the time of injury. Up to 90% of a tendon can be lacerated with preserved range of motion without resistance, so test function against resistance. Pain along the course of the tendon suggests a partial laceration even if strength is normal. Extensor tendon repair can often be performed by the emergency physician. Flexor tendon repair should be performed by the hand surgeon. It is common for the ED care of tendon lacerations to consist of closing the skin and splinting until definitive repair by the hand surgeon. Follow-up and rehabilitation of all tendon injuries are necessary, even those not requiring repair.
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Mallet finger results when complete rupture of the extensor tendon occurs at the level of the distal phalanx. On examination, the distal interphalangeal (DIP) joint is flexed at 40°. Splint the DIP joint in slight hyperextension.
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Boutonniere deformity results from an injury at the dorsal surface of the proximal interphalangeal (PIP) joint that disrupts the extensor hood apparatus. Lateral bands of the extensor mechanism become flexors of the PIP joint and hyperextensors of the DIP joint. Splint the PIP joint in extension.
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DIP joint dislocations are uncommon because of the firm attachment of skin and fibrous tissue to underlying bone. Dislocations are usually dorsal. Reduction is performed under digital block anesthesia. The dislocated phalanx is distracted, slightly hyperextended, then repositioned. Splint the joint in full extension. An irreducible joint may ...