Page 185 - Handbook of Biomechatronics

Upper-Limb Prosthetic Devices 183

Fig. 2 Above-elbow body-powered prosthesis configuration. The same configuration as
the below-elbow body-powered prosthesis (Fig. 1) is used with the addition of
a Bowden cable for switching control of elbow flexion-extension to terminal device
opening-closing. (From Northwestern University Prosthetics Research Laboratory (NUPRL).)

For the case of an above the elbow amputee an additional Bowden
cable is used to switch the control of opening and closing to elbow flex-
ion and extension (Fig. 2). The control of both functions is achieved in a
serial fashion. The major advantage of body-powered prostheses is that
the Bowden cable supplies an interconnection between the amputee
and the prosthesis, through which amputees feel that they control an
extension of their body. Other advantages include that body-powered
prostheses are of low cost, durable, and lightweight. Their disadvantages
are that they require a harness to be worn, which is uncomfortable, they
have limited range of motion, and all the needed power has to be pro-
duced by the muscular system of the amputee. There is no energy
enhancement in body-powered systems. An alternative of using a harness
and still have body-powered topology is a muscle cineplasty or exterior-
ized tendons procedure. With these surgical techniques one eliminates
the disadvantage of being uncomfortable with the harness and the limited
range of motion, but he/she ends up with other disadvantages. These dis-
advantages include an additional surgery for creating the control sites and