Pressure Between Residual Limb and Transtibial Prosthesis Socket Considering Muscle Contraction: A Finite Element Study.

Purpose: A lower-limb prosthesis is a mechanical device that replaces part of a biological limb to restore mobility. The tissues in the residual limb (the "residuum") experience atypical stresses. Importantly, the distal end of the residuum must bear the load that would typically be borne by the foot. To avoid pain and tissue damage, the part of the prosthesis that interfaces with the residuum (the "socket") must be designed to fit properly not only at rest but also during walking and other daily activities. The shape of the residuum changes during movement as muscles contract, which can affect the fit of the socket.

Methods: To study the residuum-socket interface, we created the first finite element model that considers the effect of muscle contraction on the residuum-socket interfacial pressure.

Results: During gait, the interfacial pressure at heel strike and toe off was greater in key regions of the residuum when the gastrocnemius muscle was active rather than passive. The greatest difference was observed in the popliteal fossa region during heel strike, where the pressure was 42% greater when the muscle was fully active than when passive.

Conclusion: Our results provide insight into how muscle contraction affects socket fit throughout the gait cycle, potentially leading to improvements in the design and manufacture of prosthesis sockets.