REIDER PART 1
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106 CHAn t-R 4 Hand and Wrist

Figurę 4-8. Looseness of dorsal skin.

Wrist. The bump caused by the head of the distal ulna is

the most prominent bony landmark of the dorsal wrist (Fig. 4-10). Just distal to the head of the ulna is a smali hollow marking the location of the triangular fibrocarti-lage complex (TFCC). The extensor carpi ulnaris ten-don passes over the ulnar aspect of the pronated ulna and may occasionally be visible just distal to the wrist, espe-cially if the wrist is actively extended and ulnar-deviated. The tendons of the extensors carpi radialis longus and brevis are morę apt to be visible in wrist extension, as they cross the wrist to insert at the base of the second and third metacarpals. Again, asking the patient to dorsiflex or extend the wrist actively inereases the prominence of these tendons. Active extension of the thumb also makes the tendon of the extensor pollicis longus quite visible (Fig. 4-11). This tendon enters the wrist from the center of the distal forearm, where it makes a sharply angled turn at the prominence of the radius known as Lister^łs tubercle, en route to its insertion at the base of the thumb. Bccause of the angle of approach that the FPL tendon makes with the thumb, this tendon supinates and adducts the thumb as well as extends it. Lister’s tubercle is a common site for rupture of the tendon following frac-ture of the distal radius or rheumatoid synovitis. In the case of such a rupture, the normal prominence of the tendon disappears.

Diffuse swelling over the dorsum of the wrist is common in rheumatoid arthritis or from hemorrhage following fracture of one of the carpal bones or injury to the intercarpal ligaments (Fig. 4-12A). The swelling due to synovitis is morę diffuse and extends further distally over the dorsum of the hand compared with the hematoma associated with a fracture or a ligament injury. Fracture of the distal radius is extremely common and causes swelling that is slightly morę proximal (Fig. 4-12B). When such fractures occur, the distal fragment most commonly displaces dorsally. This produces the so-called silver fork deformity, in which the distal radius and hand appear dorsally displaced with respect to the rest of the forearm (Fig. 4-12C).

A localized spherical mass on the dorsum of the wrist is most commonly due to a ganglion cyst. These cysts can