THE INSERTION OF THE EXTENSOR DIGITORUM TENDON ON THE PROXIMAL PHALANX

Review of the literature reveals that the relationship between the ext ensor digitorum muscle tendon to the proximal phalanx and the metacarp ophalangeal joint capsule remains unclear. The present study presents data about these relationships and consists of three parts: dissection of the region, high-gradient magnetic resonance imaging, and function al study. A total of 50 hands were used. Dissection was performed on 3 0, magnetic resonance studies were performed on 10, and the remaining 10 hands were used for the functional analysis. Dissection did not rev eal an insertion of the extensor digitorum tendon on the base of the p roximal phalanx. An extension of the dorsal part of the metacarpophala ngeal joint capsule running proximally toward the palmar side of the e xtensor tendon was observed in eight hands. In the remaining 22 hands, only loose connective tissue was found between the articular capsule and the tendon. The development of this tissue was variable. These obs ervations were correlated using a 7T magnetic resonance installation. The results of the functional study showed that hyperextension of the proximal phalanx increased after resection of the metacarpophalangeal structures lying under the extensor tendon. In conclusion, no real ten dinous insertion of the extensor digitorum tendon on the base of the p roximal phalanx could be found. Loose connective tissue was observed b etween the metacarpophalangeal joint capsule and the palmar aspect of the tendon, which seemed to play a secondary role in the extension of the proximal phalanx.