Preliminary investigation of the lateral postural stability of spinal cord-injured individuals subjected to dynamic perturbations

Abstract

Study Design: A study of the impact of spinal cord injury (SCI) on seated balance was conducted by comparing the results obtained from experiments with able-bodied and SCI subjects. Objectives: The purpose of this preliminary study was to examine the lateral postural stability of seated individuals with SCI in a dynamic environment. Setting: Experiments were conducted at the Cleveland Clinic Foundation in Cleveland, Ohio. Methods: Controlled perturbations were applied to each subject, seated in a wheelchair, through the use of a servo-controlled tilt platform. The platform was rotated so as to create disturbances similar in nature to those experienced in the frontal plane during left turns in a vehicle. Four quadriplegic, four paraplegic, and ®ve able-bodied subjects participated in this study. Kinematic information and center of pressure (COP) movement were recorded. Results: None of the spinal cord-injured subjects was able to maintain his stability when exposed to the stronger perturbations, while all of the able-bodied subjects stayed upright for all of the trials. On an individual basis, injury level was not always indicative of balance. However, regression results suggest a correlation between ability to perform static leaning and dynamic balance (P50.001). Conclusions: SCI subjects lost stability under dynamic conditions even though they were stable in the static situation. Initial results also raise some questions about where and when external support may be needed. Information of this nature could help to guide the design of new lateral supports with improved client acceptance.

Sitting balance and limits of stability in persons with paraplegia

“…The ability to perform both tasks can be quantified through posturographic static and dynamic tests like those conducted in our study. Although there are previous studies in which balance assessment was conducted, 15 logistical and methodological difficulties occurred in the development of the valuation, which makes it necessary to consider the protocols employed. We attempted to design an experiment with the greatest possible external validity employing a sitting position.…”

“…This result may be due to the fact that level of injury is not always a strong prognosticator of stability, 15 as many factors can influence balance, like skill, experience, tight muscles, multilevel fusion surgery, spasticity, etc. Furthermore, the classification of the injury level employed the American Spinal Injury Association Impairment Scale, 14 which does not allow differentiation of the motor level of the trunk.…”

Preserving transfer independence among individuals with spinal cord injury

“…Transfers to seats positioned higher than wheelchair seat height resulted in a shift of thè friction force' from a primarily anterior-posterior direction to a more medial-lateral direction, requiring greater biceps brachii EMG activation levels. Wang et al 45 reported that equal wheelchair seat and transfer destination heights enabled subjects to perform transfers with considerably less UE muscular e ort. Allison and Singer 46 assessed the changes in center of sitting pressure location of a patient with tetraplegia during transfer and reaching tasks with and without a specially designed orthosis, but failed to identify signi®cant di erences between conditions.…”

“…They reported that all non-impaired subjects maintained stability with all perturbations, while all individuals with a SCI failed to maintain stability when exposed to higher-level perturbations. 48 Limitations of previous investigations Several reports have examined UE kinematics, 49 ± 58 EMG activation levels, 59,60 and kinetics (ground reaction forces, pressures) 45,57,60 among individuals with SCI during wheelchair propulsion. Sitting balance characteristics among individuals with SCI have also been evaluated using kinematic, 46 ± 48 EMG activation level 17,43 and kinetic measurements.…”

“…17,46,48 Considerably less research has focused on transfers among any group of subjects, including individuals with SCI. 41,42,45 Increasing our understanding of UE function during wheelchair transfers to any of several destinations (chair, bed, commode, automobile) would increase the likelihood of intervening appropriately to decrease UE injury risk and preserve UE function. Existing studies of transfers among individuals with SCI have relied upon small groups of asymptomatic 41,42 or non-impaired subjects 45 using component UE EMG 41,42,45 or ground reaction force 45 measure-ments.…”