Assessment technique for computer-aided manufactured sockets

Abstract

Abstract-This article presents an assessment technique for testing the quality of prosthetic socket fabrication processes at computer-aided manufacturing facilities. The assessment technique is potentially useful to both facilities making sockets and companies marketing manufacturing equipment seeking to assess and improve product quality. To execute the assessment technique, an evaluator fabricates a collection of test models and sockets using the manufacturing suite under evaluation, then measures their shapes using scanning equipment. Overall socket quality is assessed by comparing socket shapes with electronic file (e-file) shapes. To characterize carving performance, model shapes are compared with e-file shapes. To characterize forming performance, socket shapes are compared with model shapes. The mean radial error (MRE), which is the average difference in radii between the two compared shapes, provides insight into sizing quality. Interquartile range (IQR), the range of radial error for the best-matched half of the points on the compared socket surfaces, provides insight into regional shape quality. The source(s) of socket shape error may be pinpointed by separately determining MRE and IQR for carving and forming. The developed assessment technique may provide a useful tool to the prosthetics community and industry to help identify problems and limitations in computer-aided manufacturing and give insight into appropriate modifications to overcome them.

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

“…The present study has shown that residuum spatial alignment can be achieved with minimal input from a user of the developed software. Recently, Zachariah et al and Sanders and Severance produced and demonstrated quantitative techniques to compare sockets, both to assess errors in CAD/CAM socket production and to monitor longitudinal residual-limb evaluation [36][37]. It was shown that weighted surface normal/mean absolute error algorithms performed better than ICP when aligning residuum shape models from repeat scans over a longitudinal period (for tracking changes over time).…”

Selecting Appropriate 3D Scanning Technologies for Prosthetic Socket Design and Transtibial Residual Limb Shape Characterization

“…Shape deviation was analysed further using a 'height' deviation, presenting the surfacesurface normal deviation data following the visualisation standard set by Sanders and Severance 15 . Deviations were mapped between each cast and a direct scan of the participant's residual limb, and between the pairs of repeat manual casts and scans.…”

Quantification of rectifications for the Northwestern University Flexible Sub-Ischial Vacuum Socket

“…Rectification maps such as those calculated in this study have been used to compare consistency of cast rectifications between prosthetists, 24 build CAD–CAM templates, 2,3,25 and assess CAM sockets. 4,5 As proposed by Sidles et al, 18 rectification maps can also be used as a tool to teach prosthetists how to modify a positive mold for specific socket designs. Additionally, Sidles et al 18 noted that the alignment used to compute rectification maps is convention-dependent: choose the alignment that minimizes the amount of material added or removed or choose an alignment that preserves anatomic landmarks known to be invariant (e.g.…”

“…1 With the advent of computer-aided design–computer-aided manufacturing (CAD–CAM), rectifications can also be accomplished by digitally manipulating either a scan of the residual limb or a scan of the negative mold of the residual limb. 1–5 In either case, rectifications are performed in a manner specific to each socket design.…”