Foot-flat Period Estimation During Daily Living Situations of Asymptomatic and Lower Limb Amputee Subjects

Abstract

Walking in various situations is a challenging task for people with a lower limb amputation. Walking upslope and downslope requires a larger ankle range of motion than waking on a level ground. Most of prosthetic feet do not include an ankle joint. The ankle mobility is obtained via the deformation of a composite structure or via rub- bers. The range of motion of the “ankle-foot” component is directly linked to the stiffness of the structure and to the load applied on the prosthesis. In ramps, prosthetic “ankle-feet” present a lack of dorsiflexion when going up and a lack of plantar flexion when going down (Williams et al. 2009). A decreased “ankle-foot” range of motion results in a reduced foot-flat period (FFP) which can induce insta- bility. New systems were proposed to allow ankle-foot prostheses to adapt to slopes (Sup et al. 2009; Williams et al. 2009; Fradet et al. 2010). Foot flat evaluation during different situations within the asymptomatic population could help to define a tar- get for prosthetic design. This parameter could also be a very interesting tool for orthoprosthesist to give a feed- back of the fitting of the prosthesis to the patient (Agrawal et al. 2009). A good adaptation of the prosthetic foot to the ground should result in a longer FFP and traduce the security of the subject on its prosthesis during stance phase. In the same way, a correct toe clearance during the swing phase will correspond to a contralateral side FFP close to normal. Actually, amputee people often demon- strate vaulting during swing phase showing their fear to stumble and fall. The evaluation of this parameter is all the more interesting for comparison purpose as it is not well taken into account during nowadays prosthesis design (Williams et al. 2009). Besides, FFP can be determined from on board measurements (Mariani et al. 2013) in real life conditions. However, for the moment, there are no reference data of FFP available in the literature.