Evaluating interface pressure in a lower-limb prosthetic socket: Comparison of FEM and experimental measurements on a roll-over simulator

Abstract

Improper socket fitting in lower-limb prostheses can lead to significant complications, including pain, skin lesions, and pressure ulcers. Current suspension and socket design practices rely predominantly on visual inspection of the residual limb and patient feedback. Monitoring stress distribution at the residual limb/socket interface offers a more objective approach. Finite Element Analysis (FEA) enables to estimate interface pressure distribution prior to manufacture to provide the orthoprosthetist with quantitative data during socket rectification and interface prosthetic components selection. However, although numerous FEA models are available, few have undergone rigorous validation against experimental pressure data. Indeed, limitations of commercial pressure sensors typically include cumbersomeness or imprecision, thereby hindering systematic measurements within the socket. In this study, we introduce a low-cost, accurate pressure sensing system integrated into 3D-printed sockets for FEA validation. The system is implemented on a roll-over simulator that uses a mock limb to mimic the interaction between a transtibial residual limb and socket during the unipodal stance phase. A FEA of the simulator was then conducted, and predicted interface pressures were compared to experimental measurements at seven discrete locations. The model demonstrated a high degree of sensitivity to the geometry of the mock limb; however, with an accurate shape description, it was able to predict pressure with an average absolute error of 12 kPa. This work advances the validation of residual limb FEA for estimating residual limb/socket interface pressures. It highlights the potential of FEA for designing data-driven sockets and ultimately improve the comfort of prosthesis users.

Keywords: 3D-printing; Below-knee amputee; Finite element modeling; Interface pressure measurements; Prosthetic socket.