Design of semi-open prosthetic socket with constant force for lower limb

Prosthetic socket is a key component of the prosthesis for clinical application; its performance directly affects the adaptation of the residual limb to the prosthetic socket. There are long-term and short-term volume fluctuation of the residual limb. The volume fluctuation of the residual limb will lead to the pressure mismatch at the interface of the residual limb and the prosthetic socket, which will cause a series of skin and fit problems. The volume fluctuation of the residual limb is considered a key factor for the successful application of the prosthetic socket; its solution is imminent. The purpose of this paper is to design a prosthetic socket with a constant force unit to solve the problem of volume fluctuation of the residual limb.

Constant force extrusion for the residual limb is proposed to solve the problem in this paper. A constant force unit is designed based on the superelasticity of shape memory alloy, and a semi-open prosthetic socket embedded in the constant force unit is designed. The constant force property of prosthetic socket is optimized and verified by finite element analysis.

The constant force unit obtains a maximum constant force region of 9.36 mm at 13 mm applied displacement, and the minimum stress amplitude is 0.0264%.

The semi-open prosthetic socket may achieve constant pressure at the interface between the residual limb and prosthetic socket within a certain range of the residual limb volume change, and it has a lightweight, good heat dissipation, size adjustability, and constant interface pressure.