Incidence of carpal boss and osseous coalition: an anatomic study

To determine the incidence of a clinically evident carpal boss (bony prominence on the dorsal aspect of the second and/or third carpometacarpal joint) and by means of dissection to determine the incidence of osseous coalitions and any abnormality or absence of associated ligament anatomy in the second through fifth carpometacarpal joints in a cadaver population.

The area of the second through fifth carpometacarpal joints was dissected in 202 cadaver wrists.

Thirty-nine of the wrists had a bony prominence and partial osseous coalition between 2 or more of the capitate, trapezoid, second metacarpal, and third metacarpal bones. When an osseous coalition was present it was incomplete, located at the dorsal aspect of the joint, and there was an absence of the normal dorsal ligaments at that joint. Ten of the 87 pairs of wrists were found to have bilateral carpal bosses with partial dorsal osseous coalition. The most common location of the osseous partial coalition was between the second metacarpal and the trapezoid. There were no osseous coalitions or absence of the normal dorsal ligaments at the fourth and/or fifth carpometacarpal joints.

This study showed that there was a high percentage of partial osseous coalitions with an associated prominence of the skeletal anatomy in the general cadaver population. The etiology of the carpal boss remains unclear.