Transtibial Amputee Joint Motion has Increased Attractor Divergence During Walking Compared to Non-Amputee Gait

Abstract

The amputation and subsequent prosthetic rehabilitation of a lower leg affects gait. Dynamical systems theory would predict the use of a prosthetic device should alter the functional attractor dynamics to which the system self-organizes. Therefore, the purpose of this study was to compare the largest Lyapunov exponent (a nonlinear tool for assessing attractor dynamics) for amputee gait compared to healthy non-amputee individuals. Fourteen unilateral, transtibial amputees and fourteen healthy, non-amputee individuals ambulated on a treadmill at preferred, self-selected walking speed. Our results showed that the sound hip (p=0.013), sound knee (p=0.05), and prosthetic ankle (p=0.023) have significantly greater largest Lyapunov exponents than healthy non-amputees. Furthermore, the prosthetic ankle has a significantly greater (p=0.0.17) largest Lyapunov exponent than the sound leg ankle. These findings indicate attractor states for amputee gait with increased divergence. The increased attractor divergence seems to coincide with decreased ability for motor control between the natural rhythms of the individual and those of the prosthetic device. Future work should consider the impact of different prostheses and rehabilitation on the attractor dynamics.

Dynamic stability of superior vs. inferior body segments in individuals with transtibial amputation walking in destabilizing environments

“…4). These findings are consistent with other recent reports of similar between limb differences observed during both walking (Wurdeman et al, 2013) and running (Look et al, 2013). …”

“…3B) instability actually decreased slightly from the head to the feet. These differences in dynamic stability between AP and ML movements were not observed in previous studies that either pooled ML and AP movements into the same state spaces (Kang and Dingwell, 2009; Hak et al, 2013) or that measured only sagittal plane joint kinematics (Look et al, 2013; Wurdeman et al, 2013) or only trunk movements (Lamoth et al, 2010). Orbital stability in both movement directions (AP vs. ML) remained more similar across all body segments (Fig.…”

“…Young adults exhibited greater local dynamic instability in their shanks and feet compared to their pelvis and trunk during unperturbed walking (Kang and Dingwell, 2009). Patients with transtibial amputation exhibited increased local instability of lower extremity joint kinematics compared to able bodied persons (Wurdeman et al, 2013), but that study did not measure upper body motions. Although another study reported increased trunk instability in patients with transfemoral amputation, counterintuitively, those subjects also became more stable when they walked outdoors over irregular terrain (Lamoth et al, 2010).…”

Step activity and stride-to-stride fluctuations are negatively correlated in individuals with transtibial amputation

“…Increased stride-to-stride fluctuations have been observed in the movements of both the intact and prosthetic limbs of individuals with amputation during walking in comparison to able-bodied participants (Beurskens et al, 2014; Wurdeman et al, 2013a, 2013b). Variability is inherent in gait even in the absence of injury or pathology (Hausdorff et al, 1996; Stergiou and Decker, 2011).…”

Quantifying Muscle Fatigue of the Low Back during Repetitive Load Lifting Using Lyapunov Analysis

“…A positive LyE may indicate the presence of determinism (order) within a time series. For more details on the algorithm and calculation of LyE please refer to Wurdeman, Myers and Stergiou, 2012 [35].…”