Adjustable sockets may improve residual limb fluid volume retention in transtibial prosthesis users

Abstract

Background: Loss of residual limb volume degrades socket fit and may require accommodation.

Objectives: To examine if either of two accommodation strategies executed during resting, socket release with full socket size return and socket release with partial socket size return, enhanced limb fluid volume retention during subsequent activity.

Study design: Two repeated-measures experiments were conducted to assess the effects of socket release on limb fluid volume retention.

Methods: Limb fluid volume was monitored while participants wore a socket with a single adjustable panel. Participants performed eight activity cycles that each included 10 min of sitting and 2 min of walking. The socket's posterior panel and pin lock were released during the fifth cycle while participants were sitting. In one experiment (Full Return), the socket was returned to its pre-release size; in a second experiment (Partial Return), it was returned to 102% of its pre-release size. Short-term and long-term limb fluid volume retention were calculated and compared to a projected, No Intervention condition.

Results: Partial Return and Full Return short-term retentions and Partial Return long-term retention were greater than those projected under the control condition ( p < 0.05).

Conclusion: Socket release during resting after activity, particularly when the socket is returned to a slightly larger size, may be an effective accommodation strategy to reduce fluid volume loss in transtibial prosthesis users.

Clinical relevance: This study suggests that existing prosthetic technologies' adjustable sockets and locking pin tethers can be used in novel ways to help maintain residual limb fluid volume in active prosthesis users.

Keywords: Biomechanics of prosthetic/orthotic devices; adjustable socket and fluid volume; amputee; biomechanics; orthotic components; prosthetic design; prosthetic interface mechanics; prosthetics; testing of prosthetic.

Figures

Fig. 1.. Test prosthesis.

(a) Top view of socket with panel opened. A tether connects to the locking pin and extends distally through a hole in the socket. (b) Side view of socket showing ratcheting dial posterior distally used to draw in the tether and lock the pin, and ratcheting dial lateral proximally to draw in the panel. Plastic spacers are shown that hold the socket at the Partial Return size.

Fig. 2.. Locations of electrode for fluid volume monitoring.

Current injection electrodes (I+ and I−) were positioned on the proximal thigh and distal limb (one electrode at each location). Volume sensing electrodes were positioned between the level of the fibular head and the distal end of the tibia.

Fig. 3.. Diagram illustrating protocols for the three experiments.

S = sit, W = walk.

Fig. 4a,b.. Percent limb fluid volume differences between measured and projected data.

a: Partial Return. b: Full Return. Circles are data for each participant. Box limits indicate the 25th and 75th quartile. Line within boxes is the median. “X” inside boxes represents the mean. Graphical presentation of data from all participants is included in Appendix 2.