The PTB Supracondylar-Suprapatellar Air-Cushion Socket

The patallar-tendon-bearing supracondy­ lar, suprapatellar air cushion (PTS-AC) below-knee (BK) prosthesis is a special modi­ fication of the supracondylar, suprapatellar suspension and the air cusion socket. The air cushion principle in combination with the patella tendon-bearing (PTB) prosthesis was introduced by Lyquist, Wilson, and Radcliffe (Fig. 1), (2) in 1965. It requires more accurate casting, fitting, and fabrication, and impor­ tantly, final reduction of stump edema. We have added a refinement to the fitting and the final fabrication of prostheses for BK amputees— the "check-socket" technique, whereby during the fitting period the patient walks in the prosthesis approximately two hours, has periodic examinations for areas of irritation or excess pressure on the stump, and has adjustments made immediately. Lyquist, Wilson, and Radcliffe (2) docu­ mented the results of improved comfort and decreased proximal pressure in a controlled clinical study of five amputees, each of whom for an initial period had worn a PTB hard socket prosthesis and then each was fitted with a PTB-air cushion prosthesis. They high­ lighted their report with evidence that a