Quantifying dynamic coupling and fit degeneration of transtibial prosthetics using 3D motion capture.

Background: Assessing the fit and suitability of lower limb prosthetics is heavily reliant upon clinician observation and subjective feedback, often resulting in negative impacts on the comfort and quality of life of amputees. This is particularly important in the early stages of new socket fitment.

Objective: This paper aims to use optoelectronic motion capture to measure the 5 degree of freedom coupling effectiveness of a newly fitted prosthetic limb during the adjustment period (6 weeks) of an active transtibial amputee.

Methods: A 2-part calibration and trial data collection system was employed using Qualisys 3D motion capture, to track the relative position of limb and socket during walking trials. A single active transtibial amputee (27 male) was fitted with a new prosthetic socket and attended weekly data capture sessions using their prosthesis normally.

Results: Here, we present evidence for alteration in prosthesis-residuum coupling performance, notably, the average proximal/distal displacement (pistoning) increased from 3.36 to 10.60 mm at week 6 from the first fit, which further increased to 12.90 mm with the use of a single prosthetic sock. Participant reported Socket Comfort Score reduced from 9 to 7 during this time.

Conclusions: This pilot study provides new insight into the dynamic behavior of prosthetic sockets and could form the basis for larger studies determining a framework for safe and comfortable coupling limits.