Comparative anatomy of the ligaments and muscles of the radiocarpal joint in chimpanzees and humans

Abstract

Objectives: In the present study, we have analyzed the anatomy of the radiocarpal joint ligaments and muscles in Pan troglodytes and Homo sapiens in order to identify similarities and differences between the two species that may be related to differ- ences in hand use and function. Materials and Methods: Anatomical dissections of the ligaments and muscles of the radiocarpal joint were performed in six adult chimpanzees and 12 humans. The mass of each ligament and of the functional ligament groups were calculated relative to the total ligament mass and compared between the two species. The mass of the functional muscle groups relative to the total mass of the muscles of the radiocarpal joint was also calculated and compared between the two species. Results: The ligaments of the radiocarpal joint had similar anatomical characteristics in chimpanzees and humans. The relative mass of the palmar ligaments was greater in humans, while that of the dorsal radiocarpal ligament was greater in chimpanzees. In both species, the relative mass of the palmar and dorsal muscle groups was inversely related to that of the corresponding ligament groups. Discussion: The greater relative mass of the palmar ligaments in humans may be related to the importance of wrist extension during manipulative tasks. The greater relative mass of the dorsal radiocarpal ligament in chimpanzees may be related to the need to stabilize the radiocarpal joint in flexion, mainly during arboreal locomotion.