REIDER PART 1
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Figurę 4-6. Mucouscyst.

swelling is soft and puffy. The PIP joints are also common sites of dislocations and collateral ligament sprains. These injuries produce localized swelling and a visiblestep-off if a nonreduced dislocation is present.

Fractures may occur in any of the phalanges. They are marked by localized ecchymosis and fusiform swelling. Angular or rotational deformities may also be present. Morę complex deformities of the fingers are dis-cussed under Alignment.

The webbing at the base of the finger slants distally from the dorsal toward the volar sidc of the hand. The distal limit of the web spaces betwcen the fingers actually marks the midpoint of the proximal phalanges. The

_Chaptek 4_Hand and Wrist 105

metacarpophalangeal (MCP) joints are usually subtly visible as a series of bumps in linę with the fingers. Swelling around one of these joints following trauma usually reflects a fracture, sprain, or dislocation. Inflammatory swelling of the metacarpophalangeal joints is commonly found in rheumatoid arthritis.

Hand. The dorsal skin of the hand is normally loose and redundant (Fig. 4-8). This allows for flexion of the fingers. Chronić swelling from edema will błock fuli flexion. The extensor tendons to the four fingers are usually visi-ble as they cross the metacarpophalangeal joints. Asking the patient to forcefully hyperextend the fingers usually inereases the prominence of the extensor tendons (Fig. 4-9). Common causes of swelling over the dorsum of the hand include metacarpal fracture, hematoma, and inflammatory tenosynovitis. Because the metacarpals are subcutancous, angulation associated with fractures of their shafts is usually visible oncc the initial swelling has declined. Fracture of the metacarpal shaft just proximal to the metacarpophalangeal joint is particularly common in the fifth metacarpal, where it is known as a boxer's fracture. Such fractures often produce a dropped knuckle; the metacarpal head is depressed and its normal prominence disappears. Carpal bossing is the term for benign bony prominences that can form on the dorsum of the proximal ends of the second and third metacarpals.

The first dorsal interosseous is the most prominent muscle mass of the dorsum of the hand. Located along the radial border of the second metacarpal, the first dorsal interosseous creates a large fleshy prominence between this metacarpal and the thumb. Yisible atrophy of the first dorsal interosseous is associated with severe degrees of ulnar neuropathy, loss of ulnar nerve function. In the presence of severe ulnar neuropathy, the conse-quent atrophy of the ulnar inncrvated interosseous mus-cles makes the metacarpal shafts morę visible.

Figurę 4-7. Bouchards nodes (arrows).