Kinematics and kinetics with an adaptive ankle foot system during stair ambulation of transtibial amputees.

Conventional prosthetic feet cannot adapt to specific conditions such as walking on stairs or ramps. Amputees are therefore forced to compensate their prosthetic deficits by modifying the kinematics and kinetics of their lower limbs. The Proprio-Foot (Ossur) intends to reduce these compensation mechanisms by automatically increasing dorsiflexion during stair ambulation thanks to an adaptive microprocessor-controlled ankle. The present investigation proposes to analyze the biomechanical effects of the dorsiflexion adaptation in transtibial (TT) amputees during stair ambulation. Sixteen TT amputees and sixteen healthy controls underwent conventional 3D gait analysis. Kinematics and kinetics of the lower limbs were compared during stair ascent and descent performed by patients with the prosthetic foot set to a neutral ankle angle and with an adapted dorsiflexion ankle angle of 4 degrees . Norm distance as well as minimum and maximal values of sagittal kinematics and kinetics were calculated for comparisons between patients and control subjects. For both stair ascent and descent, an improvement of the knee kinematics and kinetics could particularly be noticed on the involved side with an increase of the knee flexion and an increase of the knee moment during stance. Therefore, despite its additional weight compared to a conventional prosthetic ankle, the Proprio-Foot should be beneficial to active TT amputees whose knee musculature strength does not constitute a handicap.