A Clinical Appraisal of the Plastic Total Contact Above Knee Prosthesis
George H. Koepke, M.D. *
Joseph P. Giacinto, C.P. *
Evaluation of fifty-one unsetected above knee amputees for whom this prosthesis has been prescribed reveals satisfactory results. A brief description is given of a fitting technique and the reaction of the stump to total contact. The advantages of this socket over other above knee sockets are apparent from its beneficial effects on several stump disorders.
About ten years ago we began supporting the soft tissue of a stump with an improvised total contact socket which would furnish partial end bearing in above- and below-knee prostheses. Pads of felt, leather, rubber and plastic foam were inserted into the ends of the sockets to provide comfortable support. In 1958. the University of California in Berkeley published the first of a series of reports that have led to vast improvements in the fabrication, filling and alignment of the patellar-tendon-bearing total-contact prosthesis. Our early clinical experiences with this prosthesis have been reported elsewhere.
The plastic total-contact above-knee prosthesis fabricated by the University of Michigan Prosthetic Shop is similar to the prostheses described by the University of California research laboratory in Berkeley and by the Veteran's Administration Prosthetic Center in New York City. A quadrilateral wooden proximal socket is designed from conventional stump measurements. This socket is about four inches long and is fitted in an adjustable casting stand (Fig. 1 ). To insure initial flexion and adduction of the socket, the distal portion of the stump protruding from the wooden socket is wrapped with plaster in the ischial weight-bearing position (Fig. 2 ). A plastic socket is subsequently fabricated from the wooden pattern and plaster cast (Fig. 3 ). Tins technique is preferred to other casting methods: it provides total contact, optimal alignment and partial ischial weight bearing. The discrepancy in the dimensions of the socket gradually changes from values of minus 1/4 to 1/4 inches at the level of the ischial tuberosity, to plus 1/4 to 1/2 inch at the end of a mid-thigh stump. Several methods of estimating end healing have been tried. Practical clinical methods include placing a piece of clay or bouncing putty, comparable in size to a small pea. in the bottom of the socket. It will be flattened with end bearing. Or the examiner's small linger is inserted through the valve opening in the non-weight bearing position to gauge the pressure exerted between the stump and the socket when the amputee has put his weight on the prosthesis.
Fig. 4
Since November 1960. the total-contact socket has been prescribed for 51 unselecled above-knee amputees. Periodic evaluations have been made of all patients for at least three months following each fitting. Only one patient rejected the socket. He was accustomed to obsolete methods of fitting and suspension and. despite a tender bony stump, preferred a plug lilting socket. Those who had previously worn open end sockets preferred the total-contact socket; they had better control of the prosthesis and were more comfortable.
The committee on Prosthetic Research and Development of the National Academy of Sciences has reported that counter pressure on the end of a stump will promote circulation and lessen edema. This clinical study supports their report. The total-contact socket is impressively effective in lessening chronic stump edema. It has also lessened fibroelastic diathesis, varicosities of the stump, and irritation about the ischial tuberosity.
The discrepancy between dimensions of socket and stump appear to be less critical if soft tissue is supported at the lower half of the stump. With such support, the tissue is displaced towards the upper half. Fewer adjustments are required In prevent the ischial tuberosity from slipping anteriorly over the brim of the ischial seat. The plastic total-contact socket seldom develops cracks, and the valve seal is easier to maintain than it is in wooden sockets. It would appear that spurs at the end of the femur do not occur more frequently in partial end bearing than in open-end sockets. A patient with a normal slump is seldom aware of end hearing, and the person with a moderately tender stump readily adapts to this socket. A tapered slump frequently takes on a more cylindrical shape after using the socket for a few months, and a bonv stump may develop small asymptomatic bursae in response to partial end bearing. Nerve pressure syndromes of phantom sensation and phantom pain are less frequent, because pressures are more widely distributed than they are in open end sockets.
The additional step needed to fabricate the plastic total-contact above-knee prosthesis is justified by the numerous advantages over other above knee sockets.
References:
- Wolcott, L.W. and Koepke, G.H.: Arch. Phys. Med. and Rehab. Vol. 43: Sept. 1962.
- Report: Jan., Feb., Mar., 1960. Biochemics Lab. Univ. Calif.-Berkeley, April 8, 1960. p. 2, 3, 4.
- Annual Report of Activities of the Committee on Prosthetics Research and Development, National Academy of Sciences, July '61 to June '62.
|
