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

Abstract

Interestingly, young and highly active people with lower limb amputation appear to maintain a similar trunk and upper body stability during walking as able bodied individuals. Understanding the mechanisms underlying how this stability is achieved after lower leg amputation is important to improve training regimens for improving walking function in these patients. This study quantified how superior (i.e., head, trunk, and pelvis) and inferior (i.e., thigh, shank, and feet) segments of the body respond to continuous visual or mechanical perturbations during walking. Nine persons with transtibial amputation (TTA) and 12 able bodied controls (AB) walked on a 2m × 3m treadmill in a Computer Assisted Rehabilitation Environment (CAREN). Subjects were perturbed by continuous pseudo random mediolateral movements of either the treadmill platform or the visual scene. TTA maintained a similar local and orbital stability in their superior body segments as AB throughout both perturbation types. However, for their inferior body segments, TTA subjects exhibited greater dynamic instability during perturbed walking. In TTA subjects, these increases in instability were even more pronounced in their prosthetic limb compared to their intact leg. These findings demonstrate that persons with unilateral lower leg amputation maintain upper body stability in spite of increased dynamic instability in their impaired lower leg. Thus, transtibial amputation does significantly impair sensorimotor function, leading to substantially altered dynamic movements of their lower limb segments. However, otherwise relatively healthy patients with unilateral transtibial amputation appear to retain sufficient remaining sensorimotor function in their proximal and contralateral limbs to adequately compensate for their impairment.

Mediolateral angular momentum changes in persons with amputation during perturbed walking

“…This participant pool has been used for previous analyses and additional information is available in those publications [6–8] and a supplementary table. TTA underwent amputation following traumatic injury (8) or osteosarcoma (1), were receiving treatment at a specialized outpatient rehabilitation facility for injured U.S. service members, and were free from orthopedic and neurological disorders of their intact limb that might have affected walking.…”

“…Individuals with lower limb amputation are mediolaterally more unstable during walking than able-bodied individuals. These differences in stability become more pronounced during walking in destabilizing environments such as a rocky surface [5] or with mediolateral surface oscillations [6–8]. …”

“…Of particular interest was how these responses differed between able-bodied controls and individuals with unilateral transtibial amputation. We adopted a paradigm of continuous platform perturbations known to induce significant mediolateral instability [6–8, 13]. Since angular momentum has been related to stability [10–12], we hypothesized that the mean range and variability of frontal plane angular momentum would be greater during platform perturbations than no perturbations.…”

“…Thus, we also hypothesized that the range and variability of whole body angular momentum would be greater in patients with transtibial amputation than in able-bodied controls. Lastly, because Beurskens et al [8] found that the prosthetic leg of individuals with transtibial amputation exhibited greater local dynamic instability than the intact leg, we hypothesized that whole body angular momentum range and variability would be greater for the prosthetic leg than the intact leg.…”

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).…”