Prosthetics Up-Date 1980: Foot and Knee Components

Prosthetics Up-Date 1980: Foot and Knee Components

H. Richard Lehneis, Ph.D., C.P.O. 

This paper is, in part, based on a lecture given by the author at the International Congress on Technical Orthopedics, 1979, in Nurenburg, Germany.

The data relating to prosthetic foot and knee components was obtained from a survey of the relative sales volume of the various components by three of the largest U.S. distributors of prosthetics components from practically all manufacturers. The distributors cooperating in this were Knit Rite, Inc., Kansas City, Missouri; Northeast Paramedical Industries, New York, New York; and PEL Supply Company, Cleveland, Ohio.

These firms were requested to provide the relative percentage of sales of the various foot (Table 1) and knee components (Table II), rather than the absolute volume of sales. The table on knee components includes conventional versus modular constructions. The average (mean) percentages  of the various prosthetic feet and knee components sold by the three firms are listed in the last columns of Tables I and II respectively. On the basis of these data, one may infer current prescription and fitting practices in the United States.

An attempt to get similar data on below-knee and above-knee suspension systems, based on the percentage of sales of supracondylar cuff, BK side joints, hip joints, suction socket valves, and Silesian belts, appeared not valid after analysing the data collected because of the possibility of various combinations of suspension systems that may be prescribed and used. It is, therefore, hoped that readers of the Newsletter will return the questionnaire on Page 10 which addresses the subject of BK and AK sockets and suspension systems with due consideration of the various possibilities of combination of suspension systems.

Discussion

Referring to Table 1, there appears to be a vastly increased use of SACH feet versus other types of prosthetic feet. This may be interpreted in terms of the far greater frequency in recent years of BK versus AK amputations due to improved surgical techniques. Although, from the author's experience, it appears that SACH feet are used to an increasing extent and with great frequency in AK prostheses.

In Table II, one notes a surprisingly low use of hydraulic mechanisms. This may be interpreted in terms of the increase in the geriatric population who, in general, do not benefit as much as younger amputees from the hydraulic systems. Support for this interpretation may be viewed in the larger percentage of safety knees, and single-axis knees with manual knee locks used which total 66 % of all knee units sold.