Postural sway and active balance performance in highly active lower-limb amputees

Objective: To determine the balance performance of active lower-limb amputees during quiet standing and under dynamic conditions. Design: Center-of-pressure excursions during quiet standing and the standing balance performance on a single axis stabilimeter was assessed in six unilateral lower-limb amputees and six able-bodied controls. Stabilimeter trials were repeated with subjects standing so that pivoting occurred either in the anteroposteior or mediolateral direction or in the mediolateral direction but with vision occluded. Results: Center-of-pressure excursions were significantly greater (P < 0.05) for amputees in both the mediolateral and anteroposterior directions. During all stabilimeter tests, amputees spent significantly less time in balance than able-bodied controls (P < 0.05), and this was attributed to a nonsignificant increase in the average time the stabilimeter spent in contact with the ground. Group differences in the average time of contact in the anteroposterior test condition were meaningful (effect size, 1.19). Conclusions: Amputees had poorer static and dynamic balance than able-bodied controls. Amputees had a greater problem controlling dynamic balance in the anteroposterior direction than the mediolateral direction. Findings highlight the importance of the ankle in maintaining balance in situations that involve body movements in the sagittal plane.