Postural movement strategies during sensory alterations in transtibial amputees: A comparative study with able-bodied subjects

Reorganization of movement strategies is crucial in a person with lower-limb amputation to maintain postural balance during upright standing. This study aims to disentangle the contribution of movement strategies in anterior-posterior and medial-lateral directions in predicting the overall postural stability. The overall (OSI), anterior-posterior (APSI) and medial-lateral (MLSI) stability indexes were measured during standing with various sensory conditions by using computerized posturography. Postural stability of amputees was assessed while wearing three types of prosthetic feet: solid ankle cushion heel (SACH), single axis (SA) and energy storage and return (ESAR). We compared the movement strategies of ten unilateral transtibial amputees with nine able-bodied controls using the correlation analysis. The results indicated that amputees exhibited strong to very strong relationship (r= 0.82-0.99) between the OSI and MLSI score in all sensory conditions, in comparison with able-bodied group (r=0.10-0.90). Meanwhile, amputees showed very weak to very strong relationship (r=0.15-0.97) between the OSI and APSI score in comparison with able-bodied group (r=0.96-0.99). This study showed that a consistent strong relationship between OSI-MLSI was found in amputees group as for OSI-APSI in able-bodied group. Thus, movement strategies in below-knee amputees occurred most in medial-lateral direction compared to anterior-posterior direction in able-bodied group.