The influence of a microprocessor-controlled hydraulic ankle on the kinetic symmetry of trans-tibial amputees during ramp walking: A case series

Introduction Asymmetrical limb loading is believed to cause health problems for lower limb amputees and is exacerbated when walking on slopes. Hydraulically damped ankle-feet improve ground compliance on slopes compared to conventional prosthetic feet. Microprocessor-controlled hydraulic ankle-feet provide further adaptation by dynamically adjusting viscoelastic damping properties. Method Using a case series design, gait analysis was performed with four trans-tibial amputees. There were two walking conditions (ramp ascent and descent) and two prosthetic foot conditions (microprocessor-control on and off – MPF-on and MPF-off). Total support moment integral (MIsup) and degree-of-asymmetry were compared across foot conditions. Results During ramp descent, the transition of prosthetic ankle moment from dorsiflexion to plantarflexion occurred earlier in stance phase with MPF-on, slowing the angular velocity of the shank. During ramp ascent, the MPF-on dorsiflexion/plantarflexion moment transition occurred later, meaning less resistance to shank rotation in early stance and increasing walking speed by up to 6%. For both slope conditions, sound limb MIsup was universally decreased with MPF-on (4–13% descent, 3–11% ascent). Discussion Microprocessor-control of hydraulic ankle-feet reduced the total loading of the sound limb joints, for both walking conditions, for all participants. This may have beneficial consequences for long-term joint health and walking efficiency.