Prosthetic Categories

Ischial Containment vs. Subischial Sockets: What’s the Difference?

    Ischial containment prosthetic sockets were introduced in the 1980s for above-knee prosthetic users. These sockets contain the ischial tuberosity or the sitz bones, hence the name. Meanwhile, subischial sockets, which consist of upper trimlines that don’t interact with the pelvis, are relatively new.

     Researchers conducted a trial to determine how ischial containment and subischial sockets affects gait.

    So, researchers sought to understand how the two prosthetic socket designs affect the gait biomechanics of individuals with above-knee limb loss.

    Researchers, led by Stefania Fatone, Ph.D., compared the Northwestern University Flexible Sub-Ischial Vacuum (NU-FlexSIV) Socket to an ischial containment socket. They employed a randomized crossover trial method to ensure a balanced comparison and reduce bias.

    A total of 25 above-knee amputees participated in the study: 18 individuals completed the study, while seven submitted partial data. They were instructed to wear two custom-fabricated sockets full-time for seven weeks.

    Subischial prosthetic socket designed by Northwestern University.

    The Northwestern University Flexible Sub-Ischial Vacuum (NU-FlexSIV) Socket

    The researchers found that there were no significant differences in any gait variables at self-selected average walking speed for the participants who had complete data for both sockets. 

    However, after evaluating all participants and points, the researchers discovered a significant effect of the socket type on the prosthetic side front-to-back plane hip range of motion. The subischial socket exhibited a significantly greater range of motion than other sockets during self-selected normal walking speed.

    After conducting the trial, the researchers determined that using a subischial socket instead of an ischial containment socket did not significantly impact how people with unilateral above-knee amputations walk or the stability of their hip motion and coronal plane socket.