Energy Storage and Return Prostheses: A Review of Mechanical Models

Conventional lower-limb mechanical models were originally developed for gait analysis of ablebodied Conventional lower-limb mechanical models were originally developed for gait analysis of ablebodied subjects and therefore potentially misrepresent prosthetic foot behavior when applied to modern energy storage and return (ESAR) prostheses. This review investigates the limitations of current models of prosthetic foot dynamics and kinematics. The Scopus online database was used to identify 236 articles on prosthetic foot behavior during either experiments or simulations, categorized into three main types of models: 74% (n = 175) of studies featured a rigid-link model, 17% (n = 39) a lumped-parameter model and 10% (n = 23) finite element (FE) analysis. Notably, 64% (n = 152) of the studies used a conventional two-link segment model, yet only 8% (n = 20) featured the rigid, articulating prosthesis that satisfies this model's underlying rigid-body mechanics assumptions. Conversely, the available preliminary studies on multi-link segment, lumped-parameter and FE models present viable and more mechanically relevant alternatives to conventional techniques, particularly for ESAR prostheses. Expanding these alternative models to include inertial behavior, multiple-degrees of freedom and standardization of boundary conditions will lead towards both accurate and standardized prosthetic foot analysis.