Chapter 170. Hand and Wrist Injuries

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.

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.

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.

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.

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 be from an entrapped volar plate, profundus tendon, or avulsion fracture.

PIP joint dislocations are usually dorsal with rupture of the volar plate. Closed reduction is as described above for the DIP joint. Splint the joint in 30° flexion. Lateral dislocation results from rupture of one of the collateral ligaments. An irreducible joint from an entrapped volar plate or complete ligamentous disruption may require surgical intervention.

Metacarpal phalangeal (MCP) joint dislocations are usually dorsal and require surgical reduction due to volar plate entrapment. Attempt closed reduction with the wrist flexed and pressure applied to the proximal phalanx in a distal and volar direction. Splint with the MCP joint flexed 70° to 90°.

Thumb IP joint dislocations usually involve volar plate rupture. Closed reduction is as described above for the DIP joint. Place in a thumb spica splint.

Thumb MCP dislocations are usually dorsal and involve volar plate rupture. Reduce by flexing and abducting the metacarpal and apply pressure directed distally to the base of the proximal phalanx. Place in a thumb spica splint.

Thumb MCP ulnar collateral ligament rupture (gamekeeper or skier thumb) results from forced radial abduction at the MCP joint. This is the most critical of the collateral ligament injuries since it affects pincer function. The joint capsule and volar plate are usually involved. A complete tear is diagnosed when abduction stress on the proximal phalanx causes more than 40° of radial angulation relative to the metacarpal. Place in a thumb spica splint.

Distal phalanx fractures most commonly involve the tuft. These are associated with subungual hematoma and nail bed laceration. Place a volar or hairpin splint to the DIP joint. Dorsal avulsion fracture of the base may result in mallet finger.

Proximal and middle phalanx fractures of the base and neck that are nondisplaced and stable can be treated with buddy taping. Transverse or spiral midshaft fractures or intraarticular fractures often require surgical fixation. Place a gutter splint with the MCP joint flexed at 90°, the PIP joint flexed at 20°, and the DIP joint flexed at 10°.

Metacarpal (MC) fractures that involve the fourth or fifth MC neck (boxer fracture) are the most common type. Angulation more than 20° in the fourth MC, 40° in the fifth MC, or 15° in the second or third MC should be reduced. Place an ulnar gutter splint for fractures of the fourth or fifth MC and a radial gutter splint for fractures of the second or third MC with the wrist extended at 20° and the MCP joint flexed at 90°. Thumb MC fractures usually involve the base with intraarticular involvement (Bennett and Rolando fractures). Place in a thumb spica splint.

Compartment syndrome of the hand may result from crush injury or extravasation of IV fluids. The patient will complain of pain that is out of proportion to exam findings. On examination, the hand, at a resting position, is extended at the MCP joint and slightly flexed at the PIP joint. There is tense edema and pain with passive stretch of the involved compartment. This is an orthopedic emergency.

High pressure injection injury occurs when substances in a high pressure device, such as grease, paint, or hydraulic fluid, are injected into the hand. Oil-based paint causes the most severe tissue reaction that can result in ischemia and amputation. Obtain hand and forearm radiographs searching for radiopaque substances and subcutaneous air. This is an orthopedic emergency.

Scapholunate dissociation presents with wrist tenderness and swelling at the scapholunate joint. The PA radiograph demonstrates a space between the scaphoid and lunate that is >3 mm. Treat with a radial gutter splint and prompt referral.

Perilunate and lunate dislocations are best noted on lateral wrist radiograph. In both injuries, the normal alignment of the radius-lunate-capitate (the “3 C's” sign) is lost. With a perilunate dislocation, the lunate remains aligned with the radius, but the capitate is dislocated, usually dorsal to the lunate. With a lunate dislocation, the lunate dislocates volar to the radius, but the remainder of the carpus aligns with the radius. Lunate dislocation on PA radiograph has a triangular shape, the “piece of pie” sign, and on lateral view, the “spilled teacup” sign. Emergent consult for closed reduction or surgical repair is indicated.

Carpal bone fractures are managed as summarized in Table 170-3. The scaphoid is the most common carpal bone fractured. Fracture of the scaphoid, lunate, or capitate can cause avascular necrosis of the bone. Scaphoid and lunate fractures are often not detected on plain radiographs, so ED diagnosis and treatment should be based on clinical findings alone.

Colles, Smith, and Barton fractures involve the distal radius at the metaphysis (Table 170-4). Most of these fractures can be treated with closed reduction and a sugar tong splint.

Radial styloid fracture can produce carpal instability with scapholunate dissociation as major carpal ligaments insert here. Splint the wrist in mild flexion and ulnar deviation.

Ulnar styloid fracture may result in radioulnar joint instability. Place an ulnar gutter splint with the wrist in neutral position and slight ulnar deviation.