The evolution of the Canadian-type hip-disarticulation prosthesis.

1 Assistant Director, Prosthetics Research Center, Northwestern University, 401 E. Ohio St., Chicago; formerly Research Engineer, Prosthetic Services Centre, Canadian Department of Veterans Affairs, Sunnybrook Hospital, Toronto. Not many people are amputees. Still fewer people are prosthetists. Not many amputees are hip-disarticulation cases. Hence, not many prosthetists are interested in hip-disarticulation prostheses except when occasion demands. That just about sums up the history of hipdisarticulation prosthetics. A more intensive look at the picture reveals two more or less standard approaches to the problem, but usually there are as many variations as there are limbshops. The accompanying illustrations (Figs. 1 through 6) indicate the practice, if not the principle, of conventional fitting, together with some of the variants. A study of the principles of conventional fitting is even more revealing. The guiding one seems to be this: Take one standard above-knee leg and build on to it until it can be strapped to the amputee. The practice certainly bears this out. Even the term "tilting-table prosthesis" suggests working from the leg up to the stump, instead of beginning with the amputee, who properly should be the focal point in any attempt at rehabilitation. This back-handed approach to problems is not something unique among limbfitters. The plumber is more interested in joining pipes than he is in the water requirements of a household. The airplane pilot is more concerned with the trim of the aircraft than with the comfort of the passengers' seats. The prosthetist's main interest lies in making a leg he can fit on the customer, and in so doing he has shown a considerable amount of ingenuity. Perhaps had the variations not been local in nature, more progress could have been made. Many fitters have come surprisingly close to the Canadian-type prosthesis, and no doubt others actually envisioned the basic principles without achieving the mechanical design. Generally speaking, the hip-disarticulation case has been considered very unfortunate when compared with other above-knee cases. Perhaps some of this attitude is owing to the fact that a great many cases are not of traumatic origin and that therefore the life expectancy is short. In any event, the result is that the amputee is not encouraged to expect much from his prosthesis. The usual complaints are mechanical in nature—rattling in the joints and the need for frequent repair. Accordingly, most innovations in the prostheses have been directed toward solving these mechanical problems, and more by chance than by design functional advantages evolved. Conventional hip-disarticulation prostheses are usually classified into two main categories, the saucer type and the more common tiltingtable type.