Evaluation of the influence of cyclic loading on a laser sintered transtibial prosthetic socket using Digital Image Correlation (DIC)

People with a transtibial amputation worldwide rely on their prosthetic socket to regain their mobility. Patient comfort is largely affected by the weight and strength of these prosthetic sockets. The use of additive manufacturing could give the prosthetist a range of new design possibilities when designing a prosthetic socket. These new design possibilities can in turn lead to improved socket designs and more comfortable prosthetic sockets. This new way of designing and producing prosthetic sockets radically differs from the manual traditional production process. This makes it difficult for prosthetists to understand how all these new design possibilities influence the mechanical properties of the additive manufactured prosthetic socket. Therefore there is a growing need for a method to evaluate the strength and stiffness of newly developed socket designs.We propose a method to evaluate the strength and stiffness of prosthetic sockets. A robotic gait simulator is used to apply realistic kinetics of amputee gait to the tested socket. A Digital Image Correlation (DIC) system is then used to measure the deformation of a prosthetic socket under different loading conditions. This way it is possible to check if plastic deformation will occur in the designed transtibial socket. Furthermore it is possible to assess the effect of cyclic loading on the 3D printed socket.To illustrate the proposed method, a transtibial prosthetic socket was designed using CAD software and produced with laser sintering PA12. DIC measurements were performed on this transtibial socket both before and after it was subjected to a cyclic load of 1 million cycles (mimicking realistic amputee gait).