3-D motion capture system may help justify use of dual suspension system

LAS VEGAS — Lee Childers, PhD, Alabama State University Biomechanics and Motor Control Laboratory, presented data here from a study examining the use of 3-D motion capture for gait and limb movement within the socket of a K-4 level transtibial amputee.

“This is the first time three-dimensional motion been recorded in the limb socket during gait,” Childers said at the Hanger Education Fair & National Meeting.

Childers and colleagues used a Vicon motion capture system consisting of high resolution infrared cameras mounted around the room in the gait lab that tracked markers placed on the body.

“The cool part about this system is that we have … precision that is plus or minus 0.1 mm,” Childers said. “This level of precision is very rare in motion capture and it allows us make a marker based system to understand how the limb is moving in the prosthetic socket. These equations are sophisticated so you can account for how the skin moves over the bones. Older systems are not accurate enough to do this.”

In addition to the motion capture, researchers also used a walkway using highly sensitive force platforms. “We write our own software to analyze the data,” he said. “You can start to understand how the limb moves in the prosthetic socket, the forces imposed on the socket, the moments each joint has to generate to perform each locomotor task.”

The researchers attached marker based plates between the skin and the socket liner of the study participant. Marker arrays were screwed into the base plates and exited through holes in the socket. Data was captured from the array to calculate movement in the base plate.

“Because we have markers on the residuum and additional markers on the prosthesis, we can calculate the relative motion between those two systems,” Childers said.

They tested three suspension systems — pin, knee sleeve and a combination of pin and knee sleeve — and found that the dual suspension system minimized angular movement.

Childers said patients who use a dual suspension system say “it feels better, easier to control, and it turns out there is evidence to support that. There’s a lot less pushing. Dual suspension really does minimize pain. If it turns out it does also enhance control, what I hope is that we can now use this method to provide evidence to these third party payers so we can justify the use of dual suspension systems.” – by Carey Cowles

Childers L. Revising transtibial gait: measuring limb movement in the socket. Presented at: Hanger Education Fair & National Meeting. Feb. 3-7, 2014, Las Vegas.

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