Dynamic Effectiveness Evaluation of Elevated Vacuum Suspension

Introduction: The functional purpose of lower-limb prosthetic suspension systems is to adhere the prosthesis to the residual limb of the individual with amputation. Elevated vacuum suspension, a recent advancement in suspension systems, creates subatmospheric pressure between the prosthetic socket and the interface material. This form of suspension has clinically demonstrated superior prosthetic linkage. The purpose of this study was to dynamically evaluate distal displacement for vacuum and suction suspension. Vacuum was assessed at three different levels (8 in Hg, 14 in Hg, and 20 in Hg). In addition, the relationship between distal displacement and vacuum pressure fluctuations was compared. Materials and Methods: For five subjects with transfemoral amputation, an inductive sensor was used to measure the distal displacement during ambulation. Simultaneous vacuum pressure responses were collected for comparison. Results: The average distal displacement was 2.65 (1.21) mm for suction suspension, 0.80 (0.40) mm for vacuum at 8 in Hg, 0.21 (0.15) mm for vacuum at 14 in Hg, and 0.05 (0.04) mm for vacuum at 20 in Hg. Direct correlations were also determined between fluctuations in vacuum pressure and the amount of distal displacement providing insight regarding the dynamics within a vacuum suspended prosthetic socket. Conclusions: Vacuum suspension significantly reduced the amount of vertical displacement compared with suction displacement, and a linear correlation was determined between pressure fluctuations and distal displacement with vacuum suspension.