Energy cost of walking: comparison of "intelligent prosthesis" with conventional mechanism.

OBJECTIVE To determine physiological energy cost with Blatchford's "Intelligent Prosthesis" (IP) compared to energy cost with a conventional pneumatic swing phase control (PSPC) mechanism. DESIGN Before-After trial: subjects fitted with IP walked on programmable treadmill at speeds: 6 min slow, 6 min fast, 8 min while speed changed, between slow, normal, and fast, every minute, and 6 min normal. Breath-by-breath analysis of subject's expired air determined average Vo2 (L/min) within each period. Procedure repeated after 1-week interval using PSPC prosthesis. Testing sessions supervised by experienced prosthetist. SETTING Rehabilitation centre. SUBJECTS Volunteer sample. Three men, unilateral transfemoral traumatic amputee patients, ages 39 to 59 years. Normally used ischial containment socket, Blatchford Endolite Stabilised Stance Flex knee with PSPC and Multiflex foot and ankle. INTERVENTIONS Fitting, programming, and alignment of IP (own socket) by Bioengineering Unit's resident prosthetist, IP's microprocessor programmed to facilitate five walking speeds. MAIN OUTCOME MEASURE Physiological energy cost (Vo2), of using IP compared to using PSPC mechanism. RESULTS Two subjects displayed reduced Vo2 of between 5.6% and 9.0% using IP compared to PSPC prosthesis at a pace either faster or slower than their normal pace. Third subject showed no significant change in oxygen consumption despite IP unit being heavier. All subjects displayed reduced Vo2 (averaging 4.1%) using IP for period of variable speed walking. CONCLUSIONS Although differences were small, they tend to indicate that use of the heavier IP unit lowered the energy cost of walking at speeds other than the amputee's normal pace.