Thranhardt Award-winning Lecture Focuses on Prosthetic Socket Design

Las Vegas — Maria Gerschutz, PhD, of Willow Wood, presented her
Thranhardt award-winning lecture at the 2011 American Orthotic and Prosthetic
Association National Assembly here. Her lecture, Evaluation of Prosthetic
Socket Strength: A Preliminary Investigation, evaluated the
static strength of check, co-polymer and laminated definitive prosthetic

  Maria Gerschutz

Although rare, socket failure is known to occur; therefore, amputees are
subjected to potential risk of injury. The study aimed to provide a better
understanding of current socket strength. Understanding the performance of
prosthetic sockets is important to ensure quality and to assess any further
improvements within the industry, according to Gerschutz.

“Prosthetic sockets are not subject to any formal standards; as a
result, strength and variability of prosthetic sockets are relatively
unknown,” Gerschutz told O&P Business News.

Gerschutz addressed this issue by examining the properties and strength
of prosthetic socket materials. In her study, Gerschutz examined sockets from
nine facilities — three central fabrication facilities, three private
practices and three military or VA hospitals. She requested each facility to
provide 12 sockets — four diagnostic, four co-polymer and four definitive
laminated sockets. She did not place any restrictions on materials used or
fabrication method. This allowed Gerschutz to study a cross-section of the
O&P industry’s everyday practices.

Gerschutz tested the prosthetic sockets under static conditions and
against a modified ISO10328 standard, the International Standards Organization
standard covering the structural testing of lower-limb prostheses. Previous
studies have used that standard as a basis for evaluating sockets, according to
Gerschutz. Due to the custom nature and large variance of prosthetic sockets,
it is difficult to create a rigorous standard.

“It was not surprising that the check sockets on average did not
pass the loading conditions associated with by ISO10328 because the purposes of
these sockets are static fit evaluation,” Gerschutz said. “However,
it was surprising that all of the co-polymer sockets failed to pass the
ISO10328 loading. The majority of the laminated sockets also failed to pass the
same strength loading required by other prosthetic components.”

The study demonstrated the inconsistency and large variance in
prosthetic socket strength delivered to lower limb amputees and furthers the
discussion on the appropriate levels of performance, according to Gerschutz.

“The study can also be used as basis for evaluating future
materials as they become available for the general population,” she said.

Gerschutz also discussed areas in which prosthetic sockets could be
improved. She said that the development of an industry-wide, best practices
document would help identify which practices work the best and help improve the
strength and quality of the sockets.

“Hopefully this study can bring more attention to prosthetic
sockets and become an avenue for further evaluation and exploration,” she
[Award]. Every paper that is submitted gets scrutinized
thoroughly from the committee. It is not an easy process. As we review, it
seems that eventually, two papers stand out. This paper stood out in terms of
what we really need to do to move forward and improve our understanding of
orthotics and prosthetics. Sometimes it is not a question of what, but a
question of why and how.

— Thomas V. DiBello, CO, FAAOP
American Orthotic and Prosthetic Association

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