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About the Authors:
Shane R. Wurdeman
* E-mail: [email protected]
Affiliations Biomechanics Research Building, University of Nebraska at Omaha, Omaha, Nebraska, United States of America, Advanced Prosthetics Center, Omaha, Nebraska, United States of America
Sara A. Myers
Affiliation: Biomechanics Research Building, University of Nebraska at Omaha, Omaha, Nebraska, United States of America
Adam L. Jacobsen
Affiliation: Veterans Affairs Medical Center, Omaha, Nebraska, United States of America
Nicholas Stergiou
Affiliation: Biomechanics Research Building, University of Nebraska at Omaha, Omaha, Nebraska, United States of America
Introduction
Lower limb amputation presents a major change to the patient's neuromuscular system. The loss of peripheral structures and neural endpoints creates an obstacle for the individual as they potentially learn to walk again following prosthetic rehabilitation. The neuromuscular system must learn new strategies in order to fully integrate a foreign device into its natural movement pattern. Consider prior to amputation, during the common task of walking, the neuromuscular system had developed a movement strategy that encompassed an active, biological leg. Following amputation, major components of the anatomy that led to the solution that the neuromuscular system had settled on are no longer present, thereby leaving the neuromuscular system to learn a new solution if the person is to walk again with a prosthesis. The need for the neuromuscular system to learn a new solution is not unique to limb loss, but occurs under many different pathologies affecting the neuromusculoskeletal system [1].
Contrary to other pathologies that affect the neuromuscular system's previous solution to the multiple variables involved in the task of walking, individuals with a prosthesis will find their motor control being challenged to re-learn every time a new prosthesis is introduced. A new prosthesis will change the variables that the neuromuscular system is accounting for in order to resolve upon the appropriate solution. Importantly, the movement solution that results will manifest within the subtle stride-to-stride fluctuations that are naturally occurring over multiple strides [1]. Perhaps not surprising then, previous work has indeed found altered stride-to-stride fluctuations when walking for individuals with a unilateral, transtibial prosthesis compared to their healthy counterparts [2]. More specifically, Wurdeman et al.[2] reported an increased largest Lyapunov exponent (λ) for motion about the prosthetic ankle as well as the sound leg hip and knee. The λ is...