Altered gait stability and regularity in lower limb amputees observed across different body segments

The lack of sensory feedback coupled with mechanical constraints due to the prosthetic leg increases walking instability and the risk of falling in lower limb amputees. We investigated kinematic regularity and stability of different body segments in lower limb amputees during walking to identify possible altered dynamics leading to compensatory movements. We measured the three-dimensional acceleration and angular velocity of 15 body segments during two minutes of treadmill walking at three different velocities. The maximal Lyapunov exponents and fuzzy entropy were calculated from these data to assess local dynamic stability and regularity. Probabilistic principal component analysis (PPCA) was used to select the body segments that showed the highest variability between amputees and able-bodied individuals. Amputees exhibited increased instability in acceleration patterns, particularly at low walking velocity (1 km/h), regardless of body segment and direction. Angular velocity patterns were more unstable in amputees, especially on the amputated side. Altered regularity adaptation was observed with higher velocity in amputees, with the intact side showing less adaptive patterns than controls. These results further suggest that amputees have a holistically disrupted gait and balance system. Our analysis of non-linear gait dynamics provides new insights into the complex challenges faced by amputees during walking, particularly in adapting to different gait velocities.