Detecting inter-adjustment coupling changes for transtibial adjustable prosthetic sockets: A novel motion capture model feasibility study

Prosthetic sockets provide a connection between the residual limb and prosthesis. However, this connection is non-rigid, leading to unintended prosthesis movement during functional activities. These movements can diminish socket function, cause discomfort, and damage soft tissue. Adjustable sockets allow volumetric adjustments to be made; however, their impact on this connection is unknown. This study aims to assess the feasibility of a novel motion capture model in measuring inter-adjustment level prosthetic movement changes for an adjustable socket. A single male participant with unilateral transtibial amputation was recruited, and a bespoke socket with a large adjustable posterior panel was manufactured. Relative movement and comfort of the prosthesis were measured for five socket tightness settings. The novel model detected significant changes in inter-adjustment level prosthetic movements during swing phase, in both surge and pistoning displacements. However, there was no significant difference in the range of movement over the whole gait cycle. The tightest and loosest socket adjustments produced a detectable difference in comfort. Although specific to this individual and socket design, the novel motion capture model proved effective in detecting differences in adjustable prosthetic socket performance. Quantifying the influence of changes in socket shape facilitates a greater understanding of prosthetic fit and comfort.