Influence of the pelvic bone and gluteal zone over the stress state at the interaction between the prosthetic socket and residual limb for people with transfemoral amputation.

The rehabilitation process for people with lower limb amputation represents a substantial socioeconomic, psychological, and functional challenge. Finite element analysis (FEA) has been increasingly used to investigate residual limb-socket interaction; however, the extent to which additional proximal anatomy, beyond the anatomical structures commonly included in simplified models, is necessary to adequately represent the mechanical response remains unclear. This study aimed to determine whether incorporating additional proximal anatomy, specifically the gluteal soft tissue and pelvic bone, produces mechanically significant changes in FEA results compared with simplified models that include only the femur, partial residual soft tissue, and prosthetic socket, while considering the associated increase in model complexity and computational cost. Information from 15 patients with unilateral transfemoral amputation was used to develop 45 patient-specific numerical models, comprising three anatomical configurations: Model 1 included the socket, femur, and residual soft tissue without the gluteal region; Model 2 additionally incorporated the gluteal soft tissue; and Model 3 further incorporated the pelvic bone. The models preserved each patient's actual socket geometry, with quadrilateral, semi-containment, and exomodular socket designs represented across the study population. The analysis focused on the residual limb-socket interaction. The results showed that incorporating the gluteal region and pelvic bone did not produce statistically significant differences in the magnitude of the mean contact stress (CPRESS during the gait cycle stage for Model 1: 29.757 kPa for Model 2: 32.183 kPa and for Model 3: 31.853 kPa), although changes in the spatial distribution of the stress state were observed. These findings indicate that the inclusion of additional proximal anatomy may have limited influence on global contact-stress magnitude while affecting local stress distributions. Therefore, the relevance of incorporating the pelvis and gluteal region should be considered in relation to the specific objective of the simulation and the additional computational cost. This study does not evaluate the biomechanical effect of ischial support or compare different socket designs for the same patient; rather, it evaluates the mechanical implications of increasing anatomical model fidelity while maintaining each patient's specific socket configuration.