A Syme prosthesis is also known as an ankle prosthesis. Mainly used in the prosthesis after the Syme amputation, this prosthesis can actually be regarded as a special ankle amputation BK prosthesis. It can bear weight at the end of the stump and has good compensatory function. In the past, the traditional method was to use leather for slits and metal braces to reinforce them, making the prosthetics bulky and tied with straps. The appearance and function of prosthesis have been greatly improved by using resin composite material to make full contact socket.

In order to achieve the purpose of convenient insertion and removal, effective suspension and good appearance, different socket forms and assembly structures should be selected during the design process, such as single, double layer socket and open type socket. In the selection of open socket, it is necessary to consider how to ensure the structural strength.

Syme prosthesis is usually completely supported by the stump, so the main force between the stump and the socket is the relatively simple end bearing force; The analysis of the other forces can be summarized as follows:

1) During the landing of the false heel in the gait cycle, the additional pressure of the socket on the stump acts on the posterior proximal and anterior distal ends of the stump; When the toe is off the ground, it acts on the anterior proximal end and the posterior distal end of the stump. Despite the long length of the Syme stump and the large brake arm for the socket, due to the small soft tissue coverage of the stump ankle, possible problems caused by torque pressure must be noted.

2) According to the calculation of torque and stress of the small part on the ankle of the socket, the maximum stress appears in the push off period. At this time, the internal stress of the socket makes the common failure form of the front wall compression fracture and the back wall tensile tear. In resin type, the direction of reinforcement fiber should be arranged reasonably to obtain the maximum strength directionality.

3) The sagittal deviation between the prosthetic foot and the socket will also cause changes in the bearing force distribution. The gait and qualitative effects of this change are consistent with the analysis of leg prosthesis forces.