Finite element evaluation of the effect of fingertip geometry on contact pressure during flat contact.

Several studies investigated the mechanical loads developing in the hands during the use of various products in order to enhance user's performance, increase satisfaction and lower the risk of acute and cumulative trauma disorders. Values of pressure discomfort (PDT) and pressure-pain threshold (PPT) were, hence, provided. PDT and PPT may differ significantly for each subject and area of the hand because of psychological and physiological factors. A finite element study of the effect of fingertip anthropometry and anatomy geometry on mechanical loads developed during grasping is carried out in this research in order to assess physiological aspects behind variations of PDT and PPT existing between different subjects. It is found that the underlying anatomical structure and geometry (especially of the bone) significantly affect contact pressure distributions and pressure peak values. The largest difference in peak contact pressure between two different fingertips was in fact 27% for the same applied force. Furthermore, contact pressure distributions varied significantly between different subjects. The findings of this research provide novel insight into the phenomena of human grasping and the variation of contact pressure from subject to subject.