Vacuum-Assisted Socket Suspension Compared With Pin Suspension for Lower Extremity Amputees: Effect on Fit, Activity, and Limb Volume

Abstract

Klute GK, Berge JS, Biggs W, Pongnumkul S, Popovic Z, Curless B. Vacuum-assisted socket suspension compared with pin suspension for lower extremity amputees: effect on fit, activity, and limb volume. Objective To investigate the effect of a vacuum-assisted socket suspension system as compared with pin suspension on lower extremity amputees. Design Randomized crossover with 3-week acclimation. Setting Household, community, and laboratory environments. Participants Unilateral, transtibial amputees (N=20 enrolled, N=5 completed). Interventions (1) Total surface–bearing socket with a vacuum-assisted suspension system (VASS), and (2) modified patellar tendon–bearing socket with a pin lock suspension system. Main Outcome Measures Activity level, residual limb volume before and after a 30-minute treadmill walk, residual limb pistoning, and Prosthesis Evaluation Questionnaire. Results Activity levels were significantly lower while wearing the vacuum-assisted socket suspension system than the pin suspension ( P=.0056; 38,000±9,000 steps per 2wk vs 73,000±18,000 steps per 2wk, respectively). Residual limb pistoning was significantly less while wearing the vacuum-assisted socket suspension system than the pin suspension ( P=.0021; 1±3mm vs 6±4mm, respectively). Treadmill walking had no effect on residual limb volume. In general, participants ranked their residual limb health higher, were less frustrated, and claimed it was easier to ambulate while wearing a pin suspension compared with the VASS. Conclusions The VASS resulted in a better fitting socket as measured by limb movement relative to the prosthetic socket (pistoning), although the clinical relevance of the small but statistically significant difference is difficult to discern. Treadmill walking had no effect, suggesting that a skilled prosthetist can control for daily limb volume fluctuations by using conventional, nonvacuum systems. Participants took approximately half as many steps while wearing the VASS which, when coupled with their subjective responses, suggests a preference for the pin suspension system.