Material, design, and fabrication of custom prosthetic liners for lower-extremity amputees: A review

As a physical interface, a prosthetic liner is commonly used as a transition material between the residual limb and the stiff socket. Typically made from a compliant material such as silicone, the main function of a prosthetic liner is to protect the residual limb from injuries induced by load-bearing normal and shear stresses. Compared to conventional liners, custom prosthetic lower-extremity (LE) liners have been shown to better relieve stress concentrations in painful and sensitive regions of the residual limb. Although custom LE liners have been shown to offer clinical benefits, no review article on their design and efficacy has yet been written. To address this shortcoming in the literature, this paper provides a comprehensive survey of custom LE liner materials, design, and fabrication methods. First, custom LE liner materials and components are summarized, including a description of commercial liners and their efficacy. Subsequently, digital methods used to design and fabricate custom LE liners are addressed, including residual limb biomechanical modeling, finite element-based design methods, and 3-D printing techniques. Finally, current evaluation methods of custom/commercial LE liners are presented and discussed. We hope that this review article will inspire further research and development into the design and manufacture of custom LE liners.