A finite element analysis of load distribution during donning and orthostatic posture in the ITOP hybrid subischial socket.

INTRODUCTION: Pressure and shear stresses applied to the stump of a transfemoral amputee wearing a newly designed prosthetic socket have been analyzed by a finite element modeling approach. METHODS: The new socket was developed by the Istituto Tecnico Ortopedico Preneste, and it was named the "hybrid subischial socket." This work aimed at understanding the loads' distribution on the stump surface in 2 operative conditions: at the end of the wearing phase and during the orthostatic posture. The model of the stump was composed of 4 different materials: the femoral bone, the muscle tissue, the fat, and the skin layers. Except for the bone (rigid), the biological tissues were modeled as Neo-Hookean, and their mechanical properties were taken from the literature. The socket was composed of a containment frame, made of carbon fiber composite material, a shell made of flexible silicone, and a liner made of hyperelastic silicone. RESULTS: The results of our simulation show that the main support areas are located in a proper position, in agreement with the ideal principles of this prosthetic design, and the maximum pressures are well below the pain threshold reported in the literature for the same contact areas. CONCLUSIONS: We can conclude that although the upper rim of the socket is well below the ischiatic area, the new socket design allows for a safe and comfortable support of the body weight. This is in agreement with the evidence of a good functionality and acceptance of this prosthetics gathered in the many real applications.

Community ambulation in people with lower limb amputation: An observational cohort study.

ABSTRACT: Lower limb amputation (LLA) is still a health issue requiring rehabilitation and long-term care even in industrial societies. Several studies on subjects with LLA have been focused on the efficacy of rehabilitation and factors influencing the use of prosthesis. However, literature data on the recovery of ability to walk outdoors, and thus to participate in social life in this population is limited.To investigate potential correlations between socio-demographic and clinical factors, and the use of the prosthesis for indoor and/or outdoor walking referred to as community ambulation (CA) in subjects with LLA.An observational cohort study on 687 LLA subjects was conducted. Socio-demographic and clinical characteristics of 302 subjects who received similar rehabilitative treatment with respect to the standard protocol were collected by a telephone survey with a structured questionnaire. The CA recovery, in terms of patient's autonomy and participation, assessed by Walking Handicap Scale, was considered as the main outcome.The univariate analysis demonstrated statistical significant positive correlation between CA and gender (χ2 = 3.901, P = .048); amputation level (χ2 = 24.657, P < .001); pre-LLA (χ2 = 6.338, P = .012) and current work activity (χ2 = 25.192, P < .001); prosthesis use (χ2 = 187.037, P < .01); and time from LLA (r = 0.183, P < .001); increasing age was negatively correlated with the outcome (r = -0.329, P < .001), while pain intensity was not significant. Being male (75.4%); trans-tibial (TT) amputation level (9.79%); working before (3.81%) and after LLA (7.68%); and the prosthesis use (24.63%) increased the probability of CA recovery. Multivariate binary logistic regression analysis confirmed that the prosthesis use (P < .001) and TT amputation level (P = .042) are predictors of a positive outcome (Walking Handicap Scale 4-6).These findings highlight the importance of the use of prosthesis in people with LLA for the restoration of a good capacity of participation (CA), especially in subjects with TT amputation level. The identification of predictive factors may help tailor-made rehabilitation approaches addressing an earlier reintegration to social life.