Bioenergetic comparison of a new energy-storing foot and SACH foot in traumatic below-knee vascular amputations

Abstract

In this study, the metabolic performances of a new energy-storing foot (Proteor) and of the solid-ankle cushion heel (SACH) are compared. Twelve patients with traumatic below-knee amputations (mean age: 50.0 +/- 19.9 years) and 12 patients with vascular below-knee amputations (mean age: 73 +/- 7 years) were studied. Oxygen uptake (VO2) was measured in all the subjects on a walkway at a self-selected velocity; only the subjects with traumatic amputation were tested on a level treadmill (progressive speed: 2.4-4 and 6 km/h), and then in two randomized trials: incline (+5%) and decline walking treadmill test at 4 km/h. Vascular explorations were done in the vascular patients: distal pressure measurements, pulse plethysmography, transcutaneous oxygen tension. Free walking was improved in subjects with traumatic amputation using the energy-storing foot (+6%), with a better bioenergetic efficiency (0.24 +/- 0.4mL/kg.m vs 0.22 +/- 0.04mL/kg.m). However, in subjects with vascular amputation, this foot did not produce an increased free velocity nor an improved energy cost. During the level treadmill test, the traumatic amputee subjects showed a decrease of energy expenditure with the new prosthetic foot, more significant at sufficient speed (4 km/h): 17.00 +/- 3.42 vs 14.67 +/- 2.05 mL/kg/min (p < .05). The same effect is shown during the incline (19.31 +/- 2.80 vs 16.79 +/- 2.32 mL/kg/min-p < .02) and decline walking tests (14.13 +/- 3.64 vs 11.81 +/- 1.54mL/kg/min-p < .02). There is no significant difference in cardiocirculatory effects between the two types of prosthetic foot. Despite a lower velocity, the subjects with vascular amputation exceed 70% of the maximal heart rate, with the cardiocirculatory factor being the main cause of walking restriction. The energy-storing foot should be reserved for active and fast walkers, whereas the SACH foot seems more suitable for elderly patients with amputation with a slow walk.