LAS VEGAS — There was a direct correlation between the shape of a socket and the resulting forces it exerts on the residual limb, according to a presenter at the American Orthotic & Prosthetic Association World Congress.
“I’m a prosthetist, and we’ve all made justifications for a new socket, for something like this: The patient has changed in volume, therefore they need a new socket,” Garrett Hurley, CPO, chief innovations officer and co-founder of LIM Innovations, said. “That’s essentially the justification, and we often document that with a change of limb circumference. However, what if a payer says they want evidence that a loose socket even makes a difference in outcomes. There currently isn’t a lot of literature dealing with whether fit really matters.”
Hurley and colleagues hypothesized that targeted shape changes in an adjustable socket would result in changes to the pressures applied by the socket onto the residual limb during gait. To test this, researchers recruited 10 participants to wear adjustable ischial-containment sockets equipped with strain gauges and thin force sensors. These sensors mapped pressure distribution within the socket, as well as the tension within a proximal strap. Data from the sensors were recorded while the participants performed functional tests.
Participants were told to find a perceived neutral fit for their socket, and then increase and decrease the tensioner by 25 pounds to create tighter- and looser-volume variables. Walk tests and outcome measures were recorded with these variables. Participants also recorded a socket comfort score.
According to the researchers, changes in closure system tension had a direct correlation with the relative pressure distribution. When the system was looser, patients recorded higher distal pressure and when it was tighter, pressure in proximal and ischial containment aspects of the socket increased. Functional outcome scores and socket comfort scores were at their lowest or worst at the loose setting.
“Looking at the changes here, we can see what most prosthetists would expect,” Hurley said. “This can help in our ability to validate the need for socket replacements or just sockets to accommodate volume changes in the residual limb.” – by Jason Laday
Hurley G, et al. Changes in pressure distribution with an adjustable socket. Presented at: American Orthotic & Prosthetic Association World Congress; Sept. 6-9, 2017; Las Vegas.
: Hurley reports employment with LIM Innovations.