Effects of socket size on metrics of socket fit in trans-tibial prosthesis users

The purpose of this research was to conduct a preliminary effort to identify quantitative metrics to distinguish a good socket from an oversized socket in people with trans-tibial amputation. Results could be used to inform clinical practices related to socket replacement. A cross-over study was conducted on community ambulators (K-level 3 or 4) with good residual limb sensation. Participants were each provided with two sockets, a duplicate of their as-prescribed socket and a modified socket that was enlarged or reduced by 1.8 mm (∼6% of the socket volume) based on the fit quality of the as-prescribed socket. The two sockets were termed a larger socket and a smaller socket. Activity was monitored while participants wore each socket for 4 weeks. Participants' gait; self-reported satisfaction, quality of fit, and performance; socket comfort; and morning-to-afternoon limb fluid volume changes were assessed. Visual analysis of plots and estimated effect sizes (measured as mean difference divided by standard deviation) showed largest effects for step time asymmetry, step width asymmetry, anterior and anterior-distal morning-to-afternoon fluid volume change, socket comfort score, and self-reported utility. These variables may be viable metrics for early detection of deterioration in socket fit, and should be tested in a larger clinical study.