The Effect Spinal Bracing System on Gait in Adult Scoliosis Patients

Overview

Degenerative adult scoliosis (ADS) results from age related changes leading to segmental instability, deformity and stenosis. Patients with scoliosis demonstrate an altered gait pattern.Furthermore, scoliosis patients exert 30% more physical effort than healthy subjects to ensure habitual locomotion, and this additional effort requires a reciprocal increase of oxygen consumption. Bracing has been found to reduce pain within a short time in ADS patients. A new brace has recently become available, the Peak™ Scoliosis Brace (Aspen Medical Products), designed to alleviate pain in adult patients with chronic pain secondary to scoliosis. The purpose of this study is to investigate the impact of spinal bracing using Peak™ Scoliosis Brace on pain and lower extremities kinematics of gait.

Degenerative adult scoliosis (ADS) results from age related changes leading to segmental instability, deformity and stenosis. Although the etiology is unclear, degenerative adult scoliosis is associated with progressive and asymmetric degeneration of the disc and facet joints, which typically leads to stenosis. By virtue of the narrowed spinal canal associated with the degeneration these patients frequently develop back pain, as well as leg pain, weakness, and numbness. With an aging population in the USA and an increased attention to quality of life versus cost issues in the current healthcare environment, degenerative adult scoliosis has become a considerable healthcare concern. Patients with scoliosis demonstrate an altered gait pattern.Such differences include decreased step length and reduced range of motion in the upper and lower extremities asymmetry of trunk rotation and ground reaction force in three-dimensions. Previous research found a decrease in the muscular mechanical work associated with an increase of energy cost and a decrease in the muscular efficiency in a scoliosis population compared to healthy controls. Furthermore, scoliosis patients exert 30% more physical effort than healthy subjects to ensure habitual locomotion, and this additional effort requires a reciprocal increase of oxygen consumption. This altered gait pattern demonstrated by subjects with scoliosis may be due to changes in global postural control strategies caused by pain and the spinal deformity. Previous research showed that scoliosis patients do not have impaired postural balance when compared to healthy controls, while several others did find an effect of scoliosis on postural balance. This discrepancy in findings may be due to differences in curve characteristics included and their effects on postural balance, curve types (single or double), number of different curve types, location of curves (thoracic and lumbar), and/or Cobb angles. Bracing has been found to reduce pain within a short time in ADS patients. Custom-made rigid torso braces, similar to those commonly used for children, are sometimes used in ADS patients; however, only anecdotal evidence of their efficacy is available and problems with comfort and compliance are quite frequent. A new brace has recently become available, the Peak™ Scoliosis Brace (Aspen Medical Products), designed to alleviate pain in adult patients with chronic pain secondary to scoliosis. The Peak Scoliosis Brace led to some improvement of pain at 1 month in a group of adult women with scoliosis and chronic low back pain, but the quality of life did not change significantly. This is may be due to the very short follow-up time. The effect of these braces on functional tasks and activities of daily living including walking have not been studied either. The purpose of this study is to investigate the impact of spinal bracing using Peak™ Scoliosis Brace on pain and lower extremities kinematics of gait. METHODS Design This study will be a repeated measurement design. This study will be a non-randomized, prospective, concurrent control cohort study of patients with adult degenerative scoliosis who are clinically indicated for brace intervention and will serve as their own controls via their own pre-treatment evaluation. The proposal design is based on highly recommended Bayesian Design along with the Bayesian and Gaussian analysis for such population and sample size. Sample Thirty candidates with symptomatic ADS will be enrolled. The sample size needed to approach 80% statistical power for differences between conditions was estimated from the literature.17,23,24 An effect size index of f = 0.50 was estimated. For a desired power of 80% (1 - β = 0.80) and desired α = 0.05, the effect size index requires a minimum sample size of 26. Inclusion/Exclusion Criteria Thirty spinal deformity patients will be enrolled. Patients will be classified using the adult deformity SRS-Schwab system. Radiographs made prior to brace treatment and at the two pre-defined follow-up points will be measured and recorded for each patient. Patients will report to the Spine Biomechanics Laboratory in the Texas Back Institute, be educated on the study and will be asked to provide written informed consent after their questions, if any, are answered. They will then be scheduled for a test session in the lab. Each patient will be evaluated on 2 different occasions: first day of bracing, and 2±0.5 months post-bracing. Subjects will be fitted with 22 external reflective markers. These markers will be placed based on those validated and published in the literature. A static trial will be recorded with subjects positioned in a neutral, standing posture to create a reference for defining neutral joint angles. Each subject will perform a series of over-ground gait trials with self-selected speed. On all visits, subjects will walk 10 meters, stepping on three sequenced force platforms. Subjects will perform a series of gait trials until five acceptable trials are obtained. In addition, each subject will perform 2 additional tests: 1. Timed up and go, and 6 minutes' walk test. After completion of functional testing, the brace will be fitted to each subject by a spine orthopedic surgeon before the testing. The subject will wear the fitted brace for at least 45 minutes prior to retesting. The subject will then repeat the functional testing as mentioned above. Total time required for each subject to participate in one session will be approximately 90 minutes.Three-dimensional (3D) kinematic data will be recorded at 120 Hz via a Vicon-Peak system (Vicon Nexus 2.0 Inc.). Ground reaction force (GRF) (AMTI Corp.) data will be recorded simultaneously at 1200 Hz. Spine, pelvis, hip, knee, and ankle kinematics and GRF will be analyzed using a custom MATLAB program. Clinical Data Collection Prior to each gait evaluation, patients will be asked to complete a visual analog scale (VAS) to assess back and leg pain intensity, the Oswestry Disability Index (ODI, version 2.1.a), a pain drawing to record symptom location. Patients will also complete an SRS-22r, Fear Avoidance Beliefs Questionnaire (FABQ), and Tampa Scale for Kinesiophobia (TSK) to record how their spinal deformity affects them across several physical and psycho-social domains. Long cassette sagittal and coronal radiographs will be collected at first visit before brace fitting to assess the extent of spinal deformity. As previously stated, the deformity will be measured via the SRS/Schwab deformity classification system.The bracing system to be used is the Peak Scoliosis Bracing System (Aspen Medical Product Inc., Irvine, CA). The data will be analyzed with a repeated measurement two-way ANOVA to determine differences between pre- and post-bracing measurements. A conservative alpha correction will be made within each statistical family using Bonferroni correction for the multiple dependent variables in order to avoid type I error. Data will also be analyzed to determine whether any outcomes from the gait and balance analysis correlate with patient completed assessments (pain scores) based on Pearson's R correlation.