Construct Validity of the Gait Deviation Index for People With Incomplete Spinal Cord Injury (GDI-SCI).

BACKGROUND: The Gait Deviation Index for Spinal Cord Injury (SCI-GDI) was recently proposed as a dimensionless multivariate kinematic measure based on 21 gait features derived from 3-dimensional kinematic data which quantifies gait impairment of adult population with incomplete spinal cord injury (iSCI) relative to the normative gait of a healthy group. Nevertheless, no validity studies of the SCI-GDI have been published to date. OBJECTIVE: To assess the construct validity of the SCI-GDI in adult population following iSCI. Methods. SCI-GDI data were obtained from a sample of 50 healthy volunteers and 35 adults with iSCI. iSCI group was also assessed with the following measures: 10-Meter Walk Test (10MWT) at both self-selected (SS) and maximum speeds, Timed Up and Go Test (TUGT), SS and maximum levels of the Walking Index for Spinal Cord Injury (WISCI) II, mobility items of the Spinal Cord Independence Measure III (SCIM IIIIOMob), Lower Extremity Motor Score (LEMS), and Modified Ashworth Scale (MAS). Spearman's correlation coefficient was used to investigate the relationship with the SCI-GDI. RESULTS: SCI-GDI shows strong correlation with the 10MWT (r ≥ -.716) and good correlation with LEMS (r = .638), TUGT (r = -.582), SS WISCI II levels (r = .521), and SCIM IIIIOMob (r = .501). No significant correlations were found with maximum WISCI II levels and MAS (P > .006). CONCLUSIONS: Construct validity of the SCI-GDI was demonstrated with the 10MWT, TUGT, LEMS, SCIM IIIIOMob, and SS WISCI II levels for independently walking adults with iSCI. Future work will include assessing the psychometric characteristics with a more heterogeneous sample, also considering the pediatric population.

Exoskeleton-based training improves walking independence in incomplete spinal cord injury patients: results from a randomized controlled trial.

BACKGROUND: In recent years, ambulatory lower limb exoskeletons are being gradually introduced into the clinical practice to complement walking rehabilitation programs. However, the clinical evidence of the outcomes attained with these devices is still limited and nonconclusive. Furthermore, the user-to-robot adaptation mechanisms responsible for functional improvement are still not adequately unveiled. This study aimed to (1) assess the safety and feasibility of using the HANK exoskeleton for walking rehabilitation, and (2) investigate the effects on walking function after a training program with it. METHODS: A randomized controlled trial was conducted including a cohort of 23 patients with less than 1 year since injury, neurological level of injury (C2-L4) and severity (American Spinal Cord Injury Association Impairment Scale [AIS] C or D). The intervention was comprised of 15 one-hour gait training sessions with lower limb exoskeleton HANK. Safety was assessed through monitoring of adverse events, and pain and fatigue through a Visual Analogue Scale. LEMS, WISCI-II, and SCIM-III scales were assessed, along with the 10MWT, 6MWT, and the TUG walking tests (see text for acronyms). RESULTS: No major adverse events were reported. Participants in the intervention group (IG) reported 1.8 cm (SD 1.0) for pain and 3.8 (SD 1.7) for fatigue using the VAS. Statistically significant differences were observed for the WISCI-II for both the "group" factor (F = 16.75, p < 0.001) and "group-time" interactions (F = 8.87; p < 0.01). A post-hoc analysis revealed a statistically significant increase of 3.54 points (SD 2.65, p < 0.0001) after intervention for the IG but not in the CG (0.7 points, SD 1.49, p = 0.285). No statistical differences were observed between groups for the remaining variables. CONCLUSIONS: The use of HANK exoskeleton in clinical settings is safe and well-tolerated by the patients. Patients receiving treatment with the exoskeleton improved their walking independence as measured by the WISCI-II after the treatment.

Derivation of the Gait Deviation Index for Spinal Cord Injury.

The Gait Deviation Index (GDI) is a dimensionless multivariate measure of overall gait pathology represented as a single score that indicates the gait deviation from a normal gait average. It is calculated using kinematic data recorded during a three-dimensional gait analysis and an orthonormal vectorial basis with 15 gait features that was originally obtained using singular value decomposition and feature analysis on a dataset of children with cerebral palsy. Ever since, it has been used as an outcome measure to study gait in several conditions, including spinal cord injury (SCI). Nevertheless, the validity of implementing the GDI in a population with SCI has not been studied yet. We investigate the application of these mathematical methods to derive a similar metric but with a dataset of adults with SCI (SCI-GDI). The new SCI-GDI is compared with the original GDI to evaluate their differences and assess the need for a specific GDI for SCI and with the WISCI II to evaluate its sensibility. Our findings show that a 21-feature basis is necessary to account for most of the variance in gait patterns in the SCI population and to provide high-quality reconstructions of the gait curves included in the dataset and in foreign data. Furthermore, using only the first 15 features of our SCI basis, the fidelity of the reconstructions obtained in our population is higher than that when using the basis of the original GDI. The results showed that the SCI-GDI discriminates most levels of the WISCI II scale, except for levels 12 and 18. Statistically significant differences were found between both indexes within each WISCI II level except for 12, 20, and the control group (p < 0.05). In all levels, the average GDI value was greater than the average SCI-GDI value, but the difference between both indexes is larger in data with greater impairment and it reduces progressively toward a normal gait pattern. In conclusion, the implementation of the original GDI in SCI may lead to overestimation of gait function, and our new SCI-GDI is more sensitive to larger gait impairment than the GDI. Further validation of the SCI-GDI with other scales validated in SCI is needed.

Application of the Gait Deviation Index to Study Gait Impairment in Adult Population With Spinal Cord Injury: Comparison With the Walking Index for Spinal Cord Injury Levels.

The Gait Deviation Index (GDI) is a multivariate measure of overall gait pathology based on 15 gait features derived from three-dimensional (3D) kinematic data. GDI aims at providing a comprehensive, easy to interpret, and clinically meaningful metric of overall gait function. It has been used as an outcome measure to study gait in several conditions: cerebral palsy (CP), post-stroke hemiparetic gait, Duchenne muscular dystrophy, and Parkinson's disease, among others. Nevertheless, its use in population with Spinal Cord Injury (SCI) has not been studied yet. The aim of the present study was to investigate the applicability of the GDI to SCI through the assessment of the relationship of the GDI with the Walking Index for Spinal Cord Injury (WISCI) II. 3D gait kinematics of 34 patients with incomplete SCI (iSCI) was obtained. Besides, 3D gait kinematics of a sample of 50 healthy volunteers (HV) was also gathered with Codamotion motion capture system. A total of 302 (iSCI) and 446 (HV) strides were collected. GDI was calculated for each stride and grouped for each WISCI II level. HV data were analyzed as an additional set. Normal distribution for each group was assessed with Kolmogorov-Smirnov tests. Afterward, ANOVA tests were performed between each pair of WISCI II levels to identify differences among groups (p < 0.05). The results showed that the GDI was normally distributed across all WISCI II levels in both iSCI and HV groups. Furthermore, our results showed an increasing relationship between the GDI values and WISCI II levels in subjects with iSCI, but only discriminative in WISCI II levels 13, 19, and 20. The index successfully distinguished HV group from all the individuals with iSCI. Findings of this study indicated that the GDI is not an appropriate multivariate walking metric to represent the deviation of gait pattern in adult population with iSCI from a normal gait profile when it is compared with the levels of walking impairment described by the WISCI II. Future work should aim at defining and validating an overall gait index derived from 3D kinematic gait variables appropriate for SCI, additionally taking into account other walking ability outcome measures.

Walking Ability Outcome Measures in Individuals with Spinal Cord Injury: A Systematic Review.

Walking function recovery in spinal cord injury (SCI) is tackled through several therapeutic approaches in which precise evaluation is essential. A systematic review was performed to provide an updated qualitative review of walking ability outcome measures in SCI and to analyze their psychometric properties. PubMed, Cochrane, and PEDro databases were consulted until 1 April 2020. Seventeen articles written in English were included. Five of them studied the walking index for SCI, four studied the 10 meter walk test, and two studied the six-minute walk test, the timed Up and go test, and the Berg balance scale. The rest of the articles studied the following metrics: gait profile score, spinal cord injury functional ambulation profile, five times sit-to-stand test, spinal cord injury functional ambulation inventory, spinal cord independence measure (indoors and outdoors mobility items), locomotor stages in spinal cord injury, community balance and mobility scale, and activity-based balance level evaluation scale. The choice of a single or a set of metrics should be determined by the clinician. Based on the results obtained in this review, a combination of outcome measures is proposed to assess walking ability. Future work is required to integrate a more realistic environment for walking assessment.