Relative Strength of Pylon-to-Socket Attachment Systems Used in Transtibial Composite Sockets

In Brief The purpose of this investigation was to quantify the relative structural strength of various pylon-to-socket attachment systems incorporated into transtibial prosthetic composite sockets. Five systems were tested: two “single stage lay-up” or “bolt-through” systems, and three “two stage lay-up” systems. Fifteen transtibial sockets were evaluated, three each of five different pylon-to-socket attachment systems. Two of the three sockets of each attachment type incorporated carbon reinforcement, and one of the three was constructed of Nyglass stockinette only. In all cases, a pyramid-to-pyramid receiver was used as the final connection of the socket to the pylon. All of the prosthetic systems were loaded to failure in accordance with the International Standards Organization standards for structural testing of lower limb prostheses. The experimental setup simulated the instant of maximum loading during the late stance phase of the gait cycle. Comparisons of the socket attachment systems were made on the basis of ultimate strength, strength-to-weight ratio, measurement of deflection, testing weight of the socket, and failure mode. In general, it was determined that the bolt-through systems are inherently stronger than two-stage lay-up systems. The results reveal that where the selection of a pylon-to-socket attachment system is optional, empirical data may now allow the practitioner a clinical choice. Relative structural strength of various pylon-to-socket attachment systems used in transtibial prosthetic composite sockets is quantified. Fifteen transtibial sockets are evaluated, three each of five different attachment systems. Ultimate strength and strength-to-weight ratio is determined for each system. Comparisons of the socket attachment systems are made on the basis of ultimate strength, measure-ment of deflection, testing weight of the socket, and failure mode.