van Leeuwen et al - Stress distribution and the influence of morphology during grasping in the bonobo (Pan paniscus) trapeziometacarpal joint
Project
ID: 000360997
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The thumb is a crucial structure in primate evolution due to its role in grasping, and its basal trapeziometacarpal (TMC) joint is critical to its function. The TMC joint morphology varies across primates, yet little is known about form function interaction within in the TMC joint. The purpose of this study was to investigate how the TMC joint morphology influences stress distributions within the joint during five grasping types commonly employed by bonobos (Pan paniscus). We use CT-imaging of five cadaveric bonobo forearms in five standardized positions of the hand as a basis for the generation of parametric finite element models to compare grasps employed by living bonobos. We use finite element analysis (FEA) to simulate TMC joint articular force distributions to investigate stress patterns associated with each grasp type. Inter-individual stress variations and patterns deviating from grasp expectations are analysed to identify aspects of the individual TMC joint morphology that influence joint interactions. The models show a high agreement between simulated and expected stress patterns for each of the five grasps (86% of successful simulations), while partially (52%) and fully (16%) deviating patterns were also encountered. For these deviant cases, variations of key morphological features in the bonobo TMC joint are identified to account for the deviating stress patterns. This study gives biomechanical insight in the form-function interactions in the TMC joint of the bonobo, a species under-represented in anatomical and biomechanical literature despite its endangered conservation status and close phylogenetic relation to modern humans.