CARPOMETACARPAL BOSS

By Lorenzo G. Walker, M.D.

Surgery of the Hand and Upper Extremity

Clinical Characteristics

The dorsal wrist ganglion is most often confused with the carpal boss, so named by the French physician Foille. The carpal boss is an osteoarthritic spur that develops at the base of the second and/or third carpometacarpal joints (Fig. 58-18). A firm, bony, nonmobile, tender mass is visible and palpable at the base of the carpometacarpal joints, especially when the wrist is volar flexed.

Radiologically, the mass is best visualized with the hand in 30 to 40 degrees supination and 20 to 30 degrees ulnar deviation ("carpal boss view").

The boss is more common in women (2:1), in the right hand (2:1), and between the third and fourth decades. The mass may be asymptomatic, but the patient may complain of considerable pain and aching. A small ganglion is associated with

Figure 58-19. The incision for carpal boss excision, centered over the second and third carpometacarpal joints (C, capitate; T, trapezoid; ECRB, extensor carpi radialis brevis; ECRL, extensor carpi radialis longus.)

Figure 58-18. The carpal boss involving the second carpometacarpal joint (T, trapezoid)

the carpal boss in 30 percent of cases, adding to its confusion with the more common dorsal wrist ganglion. As with the mucous cyst, successful treatment requires excision of the ganglion as well as the osteoarthritic spurring.

The most common complication is the persistence of a mass because of excision of the ganglion alone or inadequate excision of the osteophytes. Pain will persist unless all abnormal abutting surfaces have been excised. Dorsal wrist ganglions can present over the carpometacarpal joints and must be distinguished from the carpal boss with its own associated ganglion. Avoidance of injury to branches of the radial and ulnar sensory nerves is again stressed.

Radiographic appearance of a carpal boss