Local dynamic stability of lower extremity joints in lower limb amputees during slope walking

Lower limb amputees have a higher fall risk during slope walking compared with non-amputees. However, studies on amputees' slope walking were not well addressed. The aim of this study was to identify the difference of slope walking between amputees and non-amputees. Lyapunov exponents λ_S was used to estimate the local dynamic stability of 7 transtibial amputees' and 7 controls' lower extremity joint kinematics during uphill and downhill walking. Compared with the controls, amputees exhibited significantly lower λ_S in hip (P=0.04) and ankle (P=0.01) joints of the sound limb, and hip joints (P=0.01) of the prosthetic limb during uphill walking, while they exhibited significantly lower λ_S in knee (P=0.02) and ankle (P=0.03) joints of the sound limb, and hip joints (P=0.03) of the prosthetic limb during downhill walking. Compared with amputees level walking, they exhibited significantly lower λ_S in ankle joints of the sound limb during both uphill (P=0.01) and downhill walking (P=0.01). We hypothesized that the better local dynamic stability of amputees was caused by compensation strategy during slope walking.

I. Introduction

Amputees have a higher fall risk compared with non-amputees. Previous study showed that 16.5% amputees fell at least once in the surgical ward during post-operative recovery period, and injuries were sustained in 60.7% of those who fell [1]. And amputees are specially challenged by walking in complex environment, such as irregular surface, stair and slope. Former studies of amputee gait focused on level walking, stair walking, obstacle crossing and turning [2]–[5]. However, studies on amputees' slope walking were not well addressed.