There is increasing evidence to support the benefits of vacuum-assisted suspension (VAS) as a means of securing lower-limb prosthetic sockets to the residual limb. As use of VAS increases, there is need to assess comparative effectiveness of different vacuum pumps. A study published in the October 2015 issue of the Journal of Prosthetics and Orthotics presents the results of in vivo tests that were conducted to evaluate the effectiveness of two commercial electric pumps, the WillowWood LimbLogic and OttoBock Harmony e-pulse, in transfemoral sockets.
According to the study abstract, the researchers evaluated the rate and time of evacuation for each pump to achieve a clinically recommended socket-liner interface pressure of 17 in-Hg below atmospheric pressure while 18 subjects stood quietly as well as the number of times each pump reactivated during ten minutes of treadmill walking by nine subjects to reestablish 17 in-Hg below atmospheric pressure after initial evacuation. During quiet standing, each pump displayed an S-shape temporal profile of vacuum pressure until 17 in-Hg below atmospheric pressure was achieved. Across participants, the LimbLogic pulled vacuum at a faster rate than the e-pulse (62 vs. 39 in-Hg/min) and required less time to achieve the desired pressure (22 versus 27 seconds). However, the LimbLogic reactivated once during walking to account for vacuum leakage, whereas the e-pulse did not reactivate.
The researchers concluded that the small differences in outcome metrics between pumps suggests that they were comparable in terms of effectiveness for creating and maintaining VAS of transfemoral sockets. This study describes simple methods that can be used in future studies when comparing electric vacuum pump performance, they said.
