Dynamic balance of persons with unilateral upper limb absence when responding to a walking disturbance.

Background: A high prevalence of falls has been reported in individuals with upper limb absence (ULA). This prevalence is increased in upper limb prosthesis users. It is possible that ULA and prosthesis use may alter recovery mechanisms in response to a perturbation.

Research Question: The purpose of this study was to investigate the reactive response of individuals with unilateral transradial ULA to perturbations during walking compared to control participants, and to determine the effect of prosthesis use on perturbation response strategies and resultant dynamics.

Methods: 10 upper limb prosthesis users and 10 matched able-bodied control participants completed two walking treadmill tasks: 1) a steady-state walking baseline trial at 1.0 m/s, and 2) 12 perturbation trials containing an unexpected, rapid treadmill belt acceleration and deceleration while walking. Six perturbations were delivered to each leg during single limb stance. Prosthesis users completed both tasks with and without their customary prosthesis. Whole-body angular momentum ranges (L) in each plane during baseline and perturbation response were compared between prosthesis users and controls using one-sided independent t-tests. A two-way repeated measures ANCOVA, with years of prosthesis use modeled as a covariate, assessed the main and interaction effects of prosthesis use and perturbation side of L in three planes, and shoulder add-abduction and flexion-extension ranges in prosthesis users.

Results And Significance: Prosthesis users exhibited greater L than controls during baseline and perturbation response, in the sagittal-plane only. L during perturbation response was significantly greater when the prosthesis was not worn, also in the sagittal-plane only. Perturbations may present a greater recovery challenge to people with transradial ULA partially due to a mass and inertia imbalance between the sound and impaired limbs when not wearing a prosthesis. Holistic rehabilitation regimes including both prosthesis and balance training should be considered for ULA populations.