Toward a Multifunctional Hand Prosthesis


We have shown through an ergonomic analysis of prehension that the thumb uses a preferred opposition plane which intersects the palmar plane with an angle of 45 to 55 degrees. With our new hand prosthesis, an angle of 45 degrees has been chosen and a three dimensional computer aided program has been used for the design and the modeling process. The hand conceptual geometry is here based on the tridigital and lateral prehension patterns. However, because of the oblique trajectory of the thumb in the tridigital mode; this hand is very well adapted for the cylindrical sperical and hook prehension patterns. The prosthesis morphology resembles the natural hand and the five fingers are each mobilized around two joints. Moreover, each finger conforms to the shape of the object and undergoes passive flexion when pushed by an external force.

Six prototypes are actually being fitted to patients already wearing an Otto Bock hand. This enables us to alternatively compare the prehension performance of the two hand prosthesis. The results obtained to date have already permitted to identify for the new hand the following functional advantages: 1) It greatly minimizes the recourse to arm and body compensatory movements during both the approach and the utilisation phases of prehension; 2) It allows a better orientation of most of the objects held for use; 3) It improves the working visibility, the gripping stability and cosmesis of the prehension.

Grant #RS-87-15, IRSST Quebec, Canada.

Institut de readaptation de Polytechnique