Thumb interphalangeal joint extension by the extensor pollicis brevis: association with a subcompartment and de Quervain's disease.

PURPOSE: First dorsal compartment anatomy was analyzed for the presence of a separate compartment for the extensor pollicis brevis (EPB) tendon and the ability of the EPB to extend the thumb interphalangeal (IP) joint in order to determine if these characteristics were associated with each other, and with de Quervain's disease. METHODS: Two groups were studied: (1) 90 cadaver wrists, 28 to 89 years, 38 male and 52 female specimens; and (2) 143 patient wrists, 21 to 82 years, 18 men and 125 women, in which the first dorsal compartment was released for treatment of de Quervain's disease. RESULTS: The EPB was in a separate compartment in 102 of 143 of the surgical group and 18 of 90 of the cadaver group. The EPB was able to extend the IP joint in 56 of 143 of the surgical group and 19 of 90 of the cadaver group. When the EPB was able to extend the IP joint, it was in a subcompartment in 49 of 56 of the surgical group and 9 of 19 of the cadaver group. When the EPB was able to produce IP extension in the cadaver group, it was inserted on the distal phalanx or the extensor hood. CONCLUSIONS: In a substantial number of people undergoing surgery for de Quervain's disease and in cadavers, the EPB can extend the thumb IP joint. When it does, particularly in patients with de Quervain's disease, it is likely to reside in a subcompartment of the first dorsal compartment. The incidences of a subcompartment for the EPB and the ability of the EPB to extend the thumb IP joint were higher in the de Quervain's patient population than in the cadaver group.

Incidence of carpal boss and osseous coalition: an anatomic study.

PURPOSE: 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. METHODS: The area of the second through fifth carpometacarpal joints was dissected in 202 cadaver wrists. RESULTS: 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. CONCLUSIONS: 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.