Optimal circumference reduction of finger models for good prosthetic fit of a thimble-type prosthesis for distal finger amputations.

The prosthetic fit of a thimble-type esthetic silicone prosthesis was retrospectively reviewed in 29 patients who were fitted following distal finger amputations. The aim was to correlate prosthetic fit with the magnitudes of circumference reduction in the finger models used to produce the prostheses and to identify the optimum reduction for the best outcome. A good fit is achieved primarily by making the prosthesis circumferentially smaller than the segment of the residual finger (residuum) over which it "cups". The percentage reduction in circumference of the finger model against the residuum model was calculated by dividing the difference in circumference between the residuum model and the finger model by the residuum model circumference and multiplying the result by 100. The computed percentage circumference reduction in the finger models ranged from small (1-3), moderate (5-7), to large (8-9). Twelve of 15 patients whose finger models had between one to three circumference reductions had a loose prosthetic fit. Only two of 14 patients who had a larger model circumference reduction of between five to nine had loose-fitting prostheses. Two of five patients who had eight to nine model circumference reduction had an uncomfortably tight prosthetic fit. A 5-7% circumference reduction in the finger model was shown in this study to best translate into good fit of a thimble-type prosthesis for distal finger amputations.