Even if properly fitted, the posture and gait of amputee people are disturbed, leading to compensations and over-solicitations of the contralateral limb. The recent commercialization of new generation ankle-foot (NG) prosthesis is not covered by French social security insurance. The evaluation of the service delivered by these medical devices was until now a combination of multidisciplinary evaluations and patient assessments, but needs objective evaluation. Several teams reported a benefit of NG feet, mainly in terms of joint mobility, walking speed and reduction in compensations. But the main subjective improvement is in balance, both in static (more comfortable waiting position) as well as in dynamic (quality and fluidity of walking), which was poorly evaluated in amputees with NG feet. The main objective of this research is to evaluate the relevance of these NG feet in terms of static stability, on both flat and inclined surfaces.

Six transtibial subjects were included. Three NG feet (Elan^®, Propriofoot^®, Meridium^®) and the patient's usual foot were successively tested. For each foot type, after socket and alignment validation by an expert prosthetist, an acclimatization period of 15 days at home was observed. After this period, clinical, instrumental (static acquisitions of 20s on two force platforms, eyes open and closed, on flat ground and on 12% inclined slope uphill and downhill) and functional evaluations (Berg Balance Scale and Activity Specific Balance Scale) were performed. Participants observed a wash out period of 3 weeks with the usual foot before testing each NG foot. The static parameters collected were: lower limb joint angles, Center of Pressure (COP) variation, ground reaction forces (GRF), and functional scores.

In static position, a larger prosthetic ankle dorsiflexion, less compensations of the amputed lower limb, better symmetry of the GRF and increase of CoP parameters (as length of trajectory and range) were found with NG feet, compared to ESR.

The absence of postural control leads to asymmetrical posture, leading to osteoarticular complications. Ankle mobility of NG feet may allow a better balance and improve destabilizations adaptations, above all on slope, and may reduce sound limb compensations.