Technological Innovations in prosthetic socket fitting – an external method to assess the residual limb/socket interaction

Authors: Sewell, P., Noroozi, S., Davenport, P., Bascou, J., Villa, C. and Zahedi, S.

Start date: 17 November 2016

The purpose of the lower limb prosthetic socket is to adequately distribute the forces from standing and ambulation in amputees’ residual limbs. For transtibial amputees, two design philosophies predominate: the patellar tendon bearing socket (PTB) and the hydrostatic socket. The first intends to apply load selectively to regions that are considered pressure tolerant. The second tries to equalise loading across the entire surface of the residual limb. Neither approach has been shown to be entirely effective in its aims: numerous studies (i.e. Goh et al.1) demonstrate that PTB sockets apply load in a manner inconsistent with the design intent, and similarly research into pressure distribution in hydrostatic sockets show significant pressure gradients during typical activities2,3. It is clear that the biomechanics of socket load are not yet fully understood4.

Pressure distribution within the prosthetic socket is important for the comfort and function of the amputee5–7. An adequately fitting socket is required for extensive use of a functional prosthesis8. Inappropriate sockets are implicated in cases of dermatological issues9,10 and pressure injury11,12.

A novel method of quantifying the interaction of the residual limb with the socket has been developed with the aim of providing the prosthetist with a clinical tool to aid in socket fitting and enhance the understanding of socket biomechanics13-17. This method utilises an approach whereby the interactions can be assessed utilising sensors on the external surface of the socket to overcome the limitations of previously developed methods which can interfere with the interaction.

The current state-of-the-art of this technology will be reported together with parallel research being undertaken by CERAH which validates the methodology. Future clinical benefits of the method will also be discussed.

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