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

Abstract

ABSTRACT Introduction Prosthetic sockets must withstand instances of maximum 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.