RESUMO
Despite the promise of powered lower limb prostheses, existing controllers do not assist many daily activities that require continuous control of prosthetic joints according to human states and environments. The objective of this case study was to investigate the feasibility of direct, continuous electromyographic (dEMG) control of a powered ankle prosthesis, combined with physical therapist-guided training, for improved standing postural control in an individual with transtibial amputation. Specifically, EMG signals of the residual antagonistic muscles (i.e. lateral gastrocnemius and tibialis anterior) were used to proportionally drive pneumatical artificial muscles to move a prosthetic ankle. Clinical-based activities were used in the training and evaluation protocol of the control paradigm. We quantified the EMG signals in the bilateral shank muscles as well as measures of postural control and stability. Compared to the participant's daily passive prosthesis, the dEMG-controlled ankle, combined with the training, yielded improved clinical balance scores and reduced compensation from intact joints. Cross-correlation coefficient of bilateral center of pressure excursions, a metric for quantifying standing postural control, increased to .83(±.07) when using dEMG ankle control (passive device: .39(±.29)). We observed synchronized activation of homologous muscles, rapid improvement in performance on the first day of the training for load transfer tasks, and further improvement in performance across training days (p = .006). This case study showed the feasibility of this dEMG control paradigm of a powered prosthetic ankle to assist postural control. This study lays the foundation for future study to extend these results through the inclusion of more participants and activities.
RESUMO
OBJECTIVE: To examine the relationship between balance, attention, and dual-task performance in individuals with acquired brain injury. DESIGN: Cross-sectional study. SETTING: Rehabilitation center and supported living program. PARTICIPANTS: Twenty-four individuals aged 18 to 58 years (mean = 39 years) with acquired brain injury who were able to ambulate 40 ft with (29%) or without an assistive device. Fifty-eight percent were independent community ambulators. Fifty-four percent had fallen in the past 6 months; and 42% reported feeling unsteady with standing or walking. INTERVENTIONS: Participants completed a battery of balance, attention, and dual-task assessments. MAIN OUTCOME MEASURES: Balance: Berg Balance Scale (BBS), Four Square Step Test (FSST), High Level Mobility Assessment Test (HiMAT); Attention: Symbol Digit Modalities Test (SDMT), Moss Attention Rating Scale (MARS), modified for a single test session; and a walking dual-task assessment, the Walking and Remembering Test. RESULTS: Mean scores: BBS, 48 of 56; FSST, 19.6 seconds; HiMAT, 20 of 54; SDMT, 30 correct; and MARS, 80. Dual-task costs were observed with variable patterns across subjects: 48% demonstrated primarily motor slowing, 9% had reduced cognitive accuracy without motor slowing, and 35% demonstrated decrements in both tasks. Subjects with a falls history had more impaired balance (HiMAT, BBS, and FSST, all P <.026) but were not significantly different in dual-task performance or attention measures. CONCLUSIONS: The test battery matched the range of motor and cognitive abilities of the sample. Balance was more strongly related to falls history than measures of attention or dual-task performance. Injury chronicity may have allowed some subjects to develop strategies to optimize dual-task performance. Alternatively, motor slowing in dual-task conditions may be an adaptive strategy, allowing performance of multiple tasks with reduced safety risk. Further investigation in this area is warranted to clarify the utility of dual-task methods in identifying falls risk after brain injury.
