Most Positive Models Created by a Central Fabrication Facility Reported Accurate

CHICAGO – A test of 10 central fabrication
facilities found most had hit the mark when creating sockets from electronic
files, Joan E. Sanders, PhD, said at the American Academy of Orthotists
and Prosthetists Meeting and Scientific Symposium, here.

In a Thranhardt Lecture Series presentation, Sanders
shared research regarding the accuracy of carving sockets at central
fabrication facilities. For the study, each facility had three electronic
models from which to carve. Sanders compared the finished sockets against the
electronic files through a 6-hour measurement process. These measurements
yielded a less than 0.1-mm error.

While all 10 companies used the same models, volume
differences between finished product and electronic model ranged from -4.2% to
+1%. The mean radii differences ranged from 0 mm to 1.2 mm.

Sanders, an Associate Professor of Bioengineering at the
University of Washington, hypothesized that the radial error might reflect
company practices of reducing the radii to allow for a sock during forming.

“It is important to point out that company
differences did exist,” Sanders said explaining that something as simple
as a setting could cause different readings even when using the same carving


If you look into FDA regulations for medical devices
with a measuring function, there are certain regulations about these devices
— how they should be working and how often they need to be calibrated. The
CAD/CAM measuring tools should fall into this category. [Companies] are
providing a product based on these measurements and when the measurements are
faulty to start, then everything that comes after that will be faulty …
You’re talking about objectifying an electronic system, but there is a
human link in there.

— Wieland Kaphingst, Dipl.-Ing. (BME), OMM, CPO
— Innovation Manager, Bauerfeind AG

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