Persons with partial hand amputations

This paper sets out to examine the design constraints and issues involved in the development of externally powered hand prostheses in general and externally powered prosthesis for persons with partial hand amputations in particular. A prototype design that resulted from these considerations is described. Currently, there are no commercially available externally-powered partial-hand prostheses. Although a wide range of devices exists for this level of amputation, there are no partial hand prostheses that provide prehension and yet are cosmetic. In addition, the majority of mechanical hands that are available for persons with trans-radial and trans-humeral amputations are not suitable for persons with wrist disarticulations or partial-hand amputations because the resulting prostheses are too long. The authors believe that preservation of the wrist motion for positioning of the terminal device is of paramount importance to achieving maximum function and cosmesis. In a partial hand prosthesis the only space for any mechanisms is in the digits. The challenge is to be able to fit all the requisite mechanisms and electronics in this highly confined volume and still have reasonable performance. The availability of small motors (MicroMo MM1016) operating in synergy (Childress, 1973) makes such a device possible