EVALUATION OF THE MAGNITUDE OF PISTONING MOTION OF THE BELOW KNEE PROSTHESES

Abstract

The incidence of amputation varies between 2.8 and 43.9 per 100,000 of population. Nearly 43% of the lower limb amputations are below knee amputee. One of the prosthesis which has being used for transtibial is patellar-tendon-bearing prosthesis (PTB) developed in the Biomechanics laboratory of California University. It is made of socket, foot and suspension system. The main role of the suspension system is to minimize the motion occurring between residual limb and prosthesis. Any failures in the function of the suspension system increase the interface motion between stump and socket and lead to troubling issues for the prosthesis users. It is not clearly defined which types of suspension systems of this prosthesis have better performance to decrease the pistoning motions. Therefore, the aim of this research was to evaluate the effects of using different kinds of suspension systems on the magnitude of pistoning motion and also on the functional performance of the below knee prosthesis.Method: A group of 51 below knee amputee participated in this study. The main criteria for selecting the patients were having no contraindications for standing and walking with prosthesis and using the current prosthesis for at least one year. In order to evaluate the efficiency of suspension system on pistoning movement, the distance between some fixed markers on the prosthesis was measured under various weight bearing conditions.Results: The correlation between the amount of pistoning movement and the type of suspension system was not significant. However, the function of the supracondylar strap and PTB total contact was better than other systems. The amount of pistoning movement differed between left and right sides.Conclusion: The magnitude of pistoning motion of the stump is not influenced by the type of selected suspension system and the stump length.