Abstract:
It is well known that the functional capability of a prosthetic hand is less than that
of the natural hand and thus it cannot perform the majority of the tasks a natural hand
does, as well or as easily. Of the many consequences from this circumstance is that
the prosthetic hand is generally used in a support role when there is a contralateral
natural hand available. This is because the prosthesis is unable to grasp objects as
flexibly as the natural hand. It is known, from splinting studies of the wrists of
unimpaired volunteers, that if the person is not able to present the hand in the correct
orientation, even the most flexible hand cannot perform prehensile tasks easily, [1,2]. In
the prosthetic circumstance, without a wrist to orientate the hand relative to the object,
conventional terminal devices do not grasp as effectively. The user must move their
arm in a different way, that allows the prosthesis to be presented to the target in an
orientation that will facilitate a secure grasp. A result from this is that there is a very real
risk that these compensatory motions use greater ranges of motion, larger forces, or
occur more often than necessary with a natural hand. Kidd et al [3], observed that
these are three of the conditions likely to induce the changes in the musculoskeletal
system that are referred to as injuries of overuse. There are few long term studies of
the effect of overuse in prosthesis wearers. It is a well known observation amongst the
clinicians that users who do not use their prostheses tend to suffer from the sort of
degenerative changes associated with overuse. Less still is known about the effect of
the compensatory actions of the contralateral limb.
