On motion and force transmission in the humanwrist: Approximating carpal bone surfaces with envelopes

Abstract

Due to its anatomic structure, the wrist is often considered the most complex joint in the human body. Despite extensive research, it remains controversial how the carpal bones interact to provide our hand with mobility, precision and strength.We applied a method for the design of cam-and-follower mechanisms to in-vivo measured data of carpal bones. The measured input data comprised the surfaces of three carpal bones (scaphoid, lunate and capitate) as well as eight poses of these bones throughout the range of motion of the hand. The resulting points on the envelope surfaces of the first two bones well approximated the surface of the latter one. This method is novel in the investigation of bone interaction since it correlates measured bone motion to bone geometry. It can be applied to adjacent bones in any joint without modification. The results are furthermore promising for the estimation of the contact area between adjoining bones. © Springer Science+Business Media Dordrecht 2013.