Volume 44 Number 3 2007
Pages 395 — 406

CAD/CAM transtibial prosthetic sockets from central fabrication facilities: How accurate are they?

Joan E. Sanders, PhD;1-2* Ellen L. Rogers, MS1; Elizabeth A. Sorenson, MSE;1 Gregory S. Lee, PhD;1 Daniel C. Abrahamson, CPO2

Departments of 1Bioengineering and 2Rehabilitation Medicine, College of Engineering and School of Medicine, University of Washington, Seattle, WA

Abstract — This research compares transtibial prosthetic sockets made by central fabrication facilities with their corresponding American Academy of Orthotists and Prosthetists (AAOP) electronic shape files and assesses the central fabrication process. We ordered three different socket shapes from each of 10 manufacturers. Then we digitized the sockets using a very accurate custom mechanical digitizer. Results showed that quality varied considerably among the different manufacturers. Four of the companies consistently made sockets within +/-1.1% volume (approximately 1 sock ply) of the AAOP electronic shape file, while six other companies did not. Six of the companies showed consistent undersizing or oversizing in their sockets, which suggests a consistent calibration or manufacturing error. Other companies showed inconsistent sizing or shape distortion, a difficult problem that represents a most challenging limitation for central fabrication facilities.

Key words: AAOP, amputee, assessment, digitizer, fabrication, patellar tendon bearing, prosthesis, rehabilitation, residual limb, shape, volume.

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