Structural integrity of custom-designed additive manufactured prosthetic sockets compared to traditional sockets

Over the past decades, the number of patients with lower extremity amputation increased world-wide. The increasing rate of patients, particularly in developing countries, has led to limited access to clinics and services for prosthetic and orthotic care. Additive manufacturing has rapidly evolved over the last decade and is opening new possibilities for prosthetics and orthotics. 3D printed prosthetic sockets are a promising solution to reduce access- or cost-related barriers to prosthesis use since 3D printed prosthetic sockets can be manufactured at an affordable cost and quickly delivered to patients. We sought to compare the ultimate strength of 3D printed sockets made of different filaments (polyethylene terephthalate glycol, polycarbonate, and co-polymer polypropylene) with that of traditionally fabricated sockets (laminated composite sockets and thermoplastic sockets) and to examine whether the strength of 3D printed sockets could be improved through iterative design changes focused on reinforcing the distal end of the socket. All sockets were mechanically tested in accordance with ISO 10328 standards. Although the strength of all of the 3D printed sockets was weaker than that of laminated composite sockets, design modifications to reinforce the distal end improved the strength of 3D printed sockets made of polycarbonate and polypropylene (but not polyethylene terephthalate glycol), resulting in ultimate strengths and stiffnesses that were comparable to the traditionally fabricated thermoplastic socket. In addition, our results demonstrated that socket failure occurred mainly at the distal end regardless of material type. The strength of some 3D printed sockets under limited testing conditions showed promise to be used for clinical purpose, especially when the socket was reinforced with distal struts.