The complexity of upper extremity control of the paralyzed patient offers a great challenge to the rehabilitation engineer, orthotist/prosthetist, or others. However, researchers can approach the problem of disabled arm motion, for the sake of simplicity, as a series of links with minimum pivots and minimum gravitational forces. In addition, when the degrees of freedom are reduced from four to three as in the case of this study, then some daily functions can be achieved by using simple braces and splints that are powered externally and internally.
In our design of a hybrid arm orthosis (HAO), we emphasized simplicity and active contribution of the user. The orthosis takes full advantage of the wheelchair frame without changing its profile. The HAO offers body powered shoulder abduction and elbow flexion of one degree of freedom. A motor-powered wrist supination and three-joint jaw chuck pinch offer the remaining two degrees of freedom.