In-silico optimization of a soft exosuit to reduce metabolic cost of walking for trans-tibial amputees

Lower limb amputations are a major lifestyle change that affects mobility and quality of life. With a growing number occurring every year and projections showing a staggering rate, developing devices to help amputees regain functionality of the lost limb has increasing importance. Many of the current state-of-the-art prosthetic devices utilize actuators and microprocessors to provide substantial assistance, although they rely on batteries that are usually heavy, bulky, and inconvenient if they run low on power. Passive devices bypass these issues since they rely on using energy storing methods. However, they have limited effectiveness in reducing the metabolic cost of gait. This study investigated the feasibility of using a soft exosuit to assist in hip flexion and extension for transtibial amputees utilizing a traditional prosthetic limb. The exosuit uses elastic bands attached at the waist and socket to provide supplementary power at the hip and knee joints. A musculoskeletal model was developed in OpenSim to simulate a trans-tibial amputee wearing a soft exosuit, and its characteristics were optimized in Matlab. Several potential solutions were discovered, with a decrease in metabolic expenditure up to 32% of the prosthetic-side when compared to the non-exosuit wielding model. This study validated our proof of concept and continued work with customizable models and human-in-the-loop optimizations could lead to exosuits that could be substantially helpful to amputees and other individuals with various gait impairments and/or in need of additional joint power.