Registering methodology for imaging and analysis of residual-limb shape after transtibial amputation

Successful prosthetic rehabilitation following lower-limb amputation depends upon a safe and comfortable socket-residual limb interface. Current practice predominantly uses a subjective, iterative process to establish socket shape, often requiring several visits to a prosthetist. This study proposes an objective methodology for residual-limb shape scanning and analysis by high-resolution, automated measurements. A three-dimensional printed "analog" residuum was scanned with three surface digitizers on 10 occasions. Accuracy was measured by the scan height error between repeat analog scans and the computer-aided design (CAD) geometry and the scan versus CAD volume. Subsequently, 20 male residuum casts from ambulatory individuals with transtibial amputation were scanned by two observers, and 10 were repeat-scanned by one observer. The shape files were aligned spatially and geometric measurements extracted. Repeatability was evaluated by intraclass correlation, Bland-Altman analysis of scan volumes, and pairwise root-mean-square error ranges of scan area and width profiles. Submillimeter accuracy was achieved when scanning the analog shape, and using male residuum casts the process was highly repeatable within and between observers. The technique provides clinical researchers and prosthetists the capability to establish their own quantitative, objective, multipatient data sets, providing an evidence base for training, long-term follow-up, and interpatient outcome comparison, for decision support in socket design.