Technique Assesses Quality of CAM Prosthetic Models and Sockets

Prosthetists may now have an assessment technique at their disposal for
evaluating the quality of prosthetic socket fabrication processes at computer-aided manufacturing facilities.

“Our intent was to create a procedure that central fabrication
facilities, prosthetic clinics, and manufacturers of CAM [computer-aided
manufacturing] equipment could use to test the manufacturing quality of the
sockets they make if they believe the product was not manufactured right,”
said Joan E. Sanders, PhD, who is a professor in the Department of
Bioengineering at the University of Washington, Seattle.

Computer-aided manufacturing employs software to control machinery when
manufacturing work pieces or products. It has been shown to reduce the time and
cost of prosthetic development by automating the mold-making and socket-forming

This, in turn, reduces the amount of manual work, and saves time and
money. The practitioner can then spend extra time with his or her patient,
according to the study, which was published in a recent issue of the
Journal of Rehabilitation Research and Development.

However, Sanders and colleagues wrote that despite the benefits of CAM,
variability in quality and consistency among different fabrication facilities
that make prosthetic models and sockets for patients with amputation is a

In fact, they said that only 24% of practitioners utilize this tool, and
inconsistent or poor performance may be an explanation for the low rate of use
for various reasons.

Their assessment technique, however, may help increase this statistic by
identifying problems and limitations in CAM. In addition, it provides much
needed insight into appropriate modifications.

CAM evaluated

Sanders and colleagues created a technique and used example results from
testing a company’s sockets to show how it worked.

The researchers used scanning equipment to measure the shapes of the
models and sockets. Results of overall socket quality were compared via the
electronic file (e-file) shapes from fabrication. Carving performance is
characterized by comparing model shapes with e-file shapes; forming performance
is characterized by comparing socket shapes with model shapes.

These quantitative analyses help to provide insight into the error and
its origin, according to the study. In addition, it provides a quick visual
assessment of overall quality.

Sanders and colleagues believe that the source of the socket shape error
could be determined by pinpointing the mean radial error (MRE) and
interquartile range (IQR) for carving and forming. MRE provides insight into
sizing quality and is the average difference in radii between the two shapes.
IQR provides insight into regional shape quality and is the average range of
radial error for the best-matched half of the points on the socket surfaces
that are being compared, according to the study.

Benefits of technique

The technique was designed to “help facilities test the quality of
their models and sockets, identify fabrication problems and limitations,
provide insight into needed equipment modifications, and document their
performance,” according to the study.

In creating this technique, Sanders said she was surprised by how much
useful information was obtained about socket manufacturing quality from these
simple metrics.

The researchers believe it could be helpful for facilities making
sockets and companies marketing the equipment who are seeking to assess and
improve product quality, according to Sanders.

“This should help them determine if they have manufacturing
problems and if so, what they might do to fix them,” Sanders told
O&P Business News. “We have had good feedback from
companies interested in using these techniques.”

The hope is that this new technique will help to enhance socket
fabrication quality, and standards for quality in the CAM industry. Added
benefits of this new assessment technique also include the ability to improve
practitioner confidence in CAM, serve as a basis for enhancement, reduce
patient health care costs, and serve as a means for documenting performance.

“The technique we describe can help facilities identify if they
have socket manufacturing errors and if they do, the sources. This should help
them determine how to fix them and thus improve their socket product,” she

The research team is currently conducting additional studies that focus
on investigating relationships between manufacturing error and clinical fit.

“We are trying to determine how accurate computer-aided design and
CAM needs to be,” Sanders said. — by Tara Grassia

For more information:

  • Sanders JE, Severance MR. Assessment technique for computer-aided
    manufactured dockets.

  • J Rehabil Res Dev. 2011;48(7):763-774.

Disclosure: Sanders reported no
relevant financial disclosures.

Leave a Reply

Your email address will not be published.