Development and evaluation of new coupling system for lower limb prostheses with acoustic alarm system
Lower limb prosthetics must have secure suspension systems to ensure minimal pistoning (movement of the socket compared to the liner) during gait. A coupling system was designed that incorporated a hollow space with a central screw, filled with silicone adhesive to allow firm attachment to a silicon liner and coupled by use of the strong magnetic field produced by a Neodymium Iron Boron magnet. This was supplemented with an acoustic alarm system, which sounded if the magnetic field could no longer be detected, signifying that the coupling has failed.
What is pistoning, and why is it a problem?
When compared to the popular pin/lock system it is shown that the new coupling has a lower tensile loading tolerance, however regains function when maximum load is removed. The new system shows significantly reduced pistoning during swing phase. The pin/ lock system allows some pistoning at initial contact, however none is seen when using the new coupling. The new coupling system can be used with or without the alarm and shows improved suspension by reduced pistoning in gait. >From: Eshraghi et al., Sci Rep 3 (2013) 2270. Published under the Creative Commons Attribution License.