Transtibial Prosthetic Socket Strength: The Use of ISO 10328 in the Comparison of Standard and 3D-Printed Sockets

Introduction: Prosthetic sockets must withstand instances ofmaximum loading without failure. The goal of the present study is to evaluate the strength at failure and the failure mechanism for 3D-printed transtibial sockets, thermoplastic transtibial check sockets, and carbon-fiber definitive laminated transtibial sockets. Materials and Methods: Three clinically available materials (carbon fiber, PETG thermoplastic, and 3D print polylactic acid [PLA]) were used to produce identically shaped sockets. In final assembly, the carbon-fiber sockets were designed for use both with and without a pin-lock system. Thermoplastic sockets and 3D-printed sockets were designed for use without a pin-lock system. These socket systems were then tested following International Standards Organization (ISO) 10328. Ultimate strength (US) at failure, maximum deflection at failure, and failure mechanism were determined. Results: Both designs of carbon-fiber sockets had higher US values at failure than thermoplastic sockets and 3D-printed PLA sockets. Thermoplastic sockets had a slightly higher average US than 3D-printed sockets, but 3D-printed sockets exhibited a greater strength-to-weight ratio. Four distinct socket failure mechanisms were determined. Conclusions: Failure mechanisms and US values differed for all socket types. Carbon-fiber sockets exhibited the highest US, but 3D-printed PLA sockets showed comparable strength to current thermoplastic sockets. Although the ISO 10328 testing standard was sufficient to complete these evaluations, the method lacked some socket-specific measures and loading conditions that could have improved comparisons between socket types.