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

Abstract

Abstract-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 3-D 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 were 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 using white light and laser scanning technologies. Scanning male residuum casts was highly repeatable within and between observers. The analysis methodology technique provides clinical researchers and prosthetists the capability to establish their own quantitative, objective, multipatient datasets. This could provide an evidence base for training, long-term follow-up, and interpatient outcome comparison, for decision support in socket design.

A Framework for Measuring the Time-Varying Shape and Full-Field Deformation of Residual Limbs Using 3-D Digital Image Correlation

“…Our system allows for the instantaneous measurement of the entire surface of the residuum, by simultaneously imaging the entire surface of the residuum using multiple synchronized cameras. Moreover, the shape registration/ alignment problem, which is typically encountered when using other scanning techniques [22], [23], is avoided entirely when using 3D-DIC, since the correspondence between surface points is inherently tracked.…”

“…Since the points in all the configurations are corresponded, this registration can be performed using closed-form solutions, which minimize the root mean square deviations between the point clouds [30], [31]. Conversely, previously used scanning methods do not provide corresponded point clouds; therefore, a closed-form solution cannot be obtained, and their alignment is therefore susceptible to local minima [22], [23]. Table 1 reports the 3D reconstruction mean and root mean square errors for each camera-pair, associated with the stereo calibration process, after applying distortion correction.…”

“…This requires an alignment/registration procedure to be applied in order to compute the difference between the shapes. Consequently, the results are dependent on the selected registration algorithm [22], [23], since there is no closed-form solution for this registration. Using our method, this problem is avoided entirely, since the correspondence between surface points is inherently tracked using 3D-DIC, thereby allowing a closed-form solution to be applied [24].…”

ampscan: A lightweight Python package for shape analysis of prosthetics and orthotics

“…Building on foundational work published by Zachariah, Sorenson and Sanders (Zachariah, Sorenson, & Sanders, 2005), in a previously published paper (Dickinson, Steer, Woods, & Worsley, 2016) we detailed a method for comparing pairs of surface scans using alignment, registration and visualisation. This enabled extraction of key measurements for evaluation of the accuracy and reliability of clinically-used scanners.…”

Measurement of the Consistency of Patella-Tendon-Bearing Modification Using Cad

“…However this was abandoned due to the large amount of variables involved. 2 When gaining measures at each landmark on Tracer, the mouse cursor was placed over the point of the landmark. However, as the system works to 0 decimal place there was a 1mm radius in which the cursor could be placed and the system stated it was directly on the landmark.…”