Effect of Prosthetic Mass Reduction on Metabolic Cost and Walking Symmetry: A Case Study on Lower Limbs

Recent human-centred design studies suggest that weight could negatively affect the physical use and psychological acceptance of a biomedical device. This aspect is especially relevant in the prosthetic field, in which heaviness is often related to device rejection. The aim of the proposed study is to inquire on the possibility to reduce the mass of a robotic leg prosthesis by topologically optimizing its structural frame. First, a finite element analysis (FEA) was performed to characterise the stress-strain response of a previously developed frame. Then, a topological optimization technique was applied to reduce weight while minimizing the frame compliance. Following the proposed methodology, the structural frame was manufactured, resulting in a 43.5% weight reduction. To validate the proposed structural optimization, walking experiments were performed, considering an able-bodied subject wearing an able-bodied adapter. The proposed solutions reduced the metabolic cost of walking by 8.4% while improving walking symmetry.