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AbstractSustained mechanical loading on skeletal muscle tissue can lead to degeneration and cell damage over time, resulting in the development of pressure ulcers, particularly in hospital mattresses or for wheelchair-bound users. The primary risk factors for this damage are tissue ischemia caused by pressure in the contact area and tissue compressive strain. In this study, a multi-cell, multi-material foam mattress for the upper comfort layer was developed, with the aim of simultaneously minimizing soft tissue compressive strain and maximum surface pressure on the human buttocks zone. The levels of these factors were estimated using the finite element method (FEM). A multi-objective optimization (MOO) approach was employed, coupling the non-dominated sorting genetic algorithm (NSGA-II) with FEM. This algorithm helped determine the required compressive strength and the optimal cell configurations to achieve the desired outcomes. The majority of the optimal solutions exhibited contact pressures (Cpresss) below the recommended threshold to avoid local tissue ischemia. The optimized cellular material configurations resulted in soft tissue compressive strain of 12% and Cpress of 3.4 kPa, indicating longer safety times for supine support on the foam mattress without the need for repositioning. The optimization process utilized 5 softer foam materials out of the 9 firmness levels tested to achieve these results. The proposed multi-cell, multi-material foam mattress model shows promise for the prevention of pressure sores, as suggested by the optimization findings. [ABSTRACT FROM AUTHOR]

AbstractRestoring mobility using prosthetic limbs anchored in custom sockets is the primary goal of amputee rehabilitation. The contact pressure at the stump-liner interface is critical for improving prosthetic socket design and enhancing amputee satisfaction and comfort. This study aimed to develop and optimize a new customized multicellular foam liner model by identifying the optimal configuration of the liner’s cells to achieve minimal contact pressure between the transtibial limb (stump) and the prosthetic interface while simultaneously minimizing the stump’s immersion in the foam liner. The study employed a multi-objective optimization using the NSGA-II genetic algorithm to optimize the material configurations of the liner cells. The objective function was based on a finite element (FE) model of the customized foam liner, composed of 40 cells, each using one of six foam materials with varying firmness. The optimization process yielded nine different configurations representing the Pareto front. Contact pressure and immersion, represented by displacement in the load direction, were reduced from 140 KPa and 9 mm to 10 KPa and less than 1 mm, respectively. The results obtained in this study motivate future clinical trials on the efficacy of customized multicellular foam liners. These findings provide in-depth insights into prosthesis design and customization, potentially leading to further development in the use of foam rather than silicone for liner manufacturing. [ABSTRACT FROM AUTHOR]

AbstractAfter lower limb amputation, the primary challenge is to facilitate the patient’s adoption of a prosthetic limb seamlessly, without encountering complications or discomfort. Elevated stress levels within the residual limb, experienced when wearing the socket and while standing or walking, contribute to patient discomfort. As an initial step in this study, we developed a finite element model of above-knee amputation. Additionally, we designed a prototype orthopedic implant composed of several parts, with the lower section featuring a honeycomb structure aimed at absorbing and diminishing stresses at the interface of the residual limb and prosthetic. In this study, finite element models with and without orthopedic implants were analyzed to assess the feasibility and impact of incorporating a honeycomb structure within the implants on stress distribution, particularly at the stump-prosthetic interface. Models with honeycomb-structured implants, at varying densities, showed a reduction in interface stress to approximately 2.15e-2 MPa and 2.01e-2 MPa, compared to 4.5e-2 MPa in model without honeycomb structure in the implant and 7.97e-2 MPa in models without any implants. [ABSTRACT FROM AUTHOR]