Three-dimensional geometric morphometric analysis of the distal radius insertion sites of the palmar radiocarpal ligaments in hominoid primates.

Objectives To identify anatomic differences in the insertion sites of the palmar radiocarpal ligaments in different species of hominoid primates that may be related to their different types of locomotion. Materials and methods We have used three-dimensional geometric morphometrics (3D GM) to analyze the distal radius ligament insertion sites in 31 Homo sapiens, 25 Pan troglodytes, 31 Gorilla gorilla, and 15 Pongo pygmaeus. We have also dissected the radioscaphocapitate (RSC), long radiolunate (LRL) and short radiolunate (SRL) ligaments in six H. sapiens and five P. troglodytes to obtain quantitative values that were then compared with the results of the 3D GM analysis. Results H. sapiens had a relatively larger insertion site of the RSC + LRL ligament than the other hominoid primates. P. pygmaeus and P. troglodytes had a relatively large SRL ligament insertion site with a palmar orientation. In G. gorilla, the two ligament insertion sites were relatively smaller and the SRL insertion site had an ulnopalmar orientation. Discussion The morphological differences observed can be related to the types of locomotion used by the different species and to quantitative data obtained from the dissection of ligaments in H. sapiens and P. troglodytes. 3D GM analysis of ligament insertion sites can help in interpreting the types of locomotion used by extinct hominoid primates through the analysis of preserved fossilized fragments of the distal radius.