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

Abstract

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.

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

“…In 2007, 24 percent of prosthetic devices in the United States were reported to incorporate the use of CAD/CAM technology [26], and although the integration of this technology may have increased since, other countries and regions have been slower to adopt it. Past deterrents included the perceived cost of scanning hardware and software, variability in the accuracy achieved by central fabrication facilities [27], and concern that the technique might distance the prosthetists from the ability to exercise their fundamental tactile and experiential skill. However, the CAD/CAM process potentially allows a wealth of data to be collected for each patient and for each prosthetist's practice.…”

Assessment technique for computer-aided manufactured sockets

“…Clearly shown in previous reports in the literature [2,10], variability exists in quality and consistency among different fabrication facilities that make prosthetic models and sockets for patients with amputation. It would therefore seem reasonable for facilities to assess their manufacturing equipment as part of their regular practice.…”

“…We are not aware of any currently available commercial products that are small enough and meet the required accuracy threshold. The contact scanner we developed had an accuracy of approximately 0.1 mm for a wide range of socket shapes tested and sampled at 800 points per slice [2] with a 0.8 mm slice spacing. These performance qualities are Diagram summarizing assessment technique.…”

“…Inconsistent or poor performance is believed to be part of the reason for low use. This is likely caused by some fabrication facilities not making the shape designed by the practitioner on the computer [2]. A wide range of quality exists in the industry.…”

Computational Modelling of Mechanical Behavior of Biological Tissues for Biomedical Applications

“…The main function of the socket is to transmit forces during the ambulation, assure prosthesis stability, hold and protect the residual limb. Currently, the socket design and manufacture still relies on an artisanal process, which is non-standard and non-repeatable resulting in non-predictable performance [13,14]. From a patient's point of view, the most important functionality of the socket is its usability, where a socket should provide the wearer at least the stability and comfort during day-to-day wearing.…”