Biomechanics of Exoskeleton-Assisted Treadmill Walking.

To exploit the benefits of treadmill-based exoskeletons, it is crucial to assess possible deviations from natural walking depending on assistive parameters. This study evaluated the biomechanics of exoskeleton-assisted treadmill walking by comparing it with free gait. Five healthy participants walked freely on a treadmill and with the assistance of the Lokomat gait trainer, while changing Body Weight Support (BWS), Gait Speed (GS), and Guidance Force (GF). Results showed that the hip and knee joint kinematics depended on BWS and GS, while changes due to GF were limited. Moreover, joint kinematics and the activity of related muscles were altered with respect to free gait, for any combination of robot parameters in the case of the ankle, and especially for low GS and with BWS in the case of hip and knee. Overall, walking with the Lokomat can mostly resemble free gait at high speed and without BWS.

Symbitron Exoskeleton: Design, Control, and Evaluation of a Modular Exoskeleton for Incomplete and Complete Spinal Cord Injured Individuals.

In this paper, we present the design, control, and preliminary evaluation of the Symbitron exoskeleton, a lower limb modular exoskeleton developed for people with a spinal cord injury. The mechanical and electrical configuration and the controller can be personalized to accommodate differences in impairments among individuals with spinal cord injuries (SCI). In hardware, this personalization is accomplished by a modular approach that allows the reconfiguration of a lower-limb exoskeleton with ultimately eight powered series actuated (SEA) joints and high fidelity torque control. For SCI individuals with an incomplete lesion and sufficient hip control, we applied a trajectory-free neuromuscular control (NMC) strategy and used the exoskeleton in the ankle-knee configuration. For complete SCI individuals, we used a combination of a NMC and an impedance based trajectory tracking strategy with the exoskeleton in the ankle-knee-hip configuration. Results of a preliminary evaluation of the developed hardware and software showed that SCI individuals with an incomplete lesion could naturally vary their walking speed and step length and walked faster compared to walking without the device. SCI individuals with a complete lesion, who could not walk without support, were able to walk with the device and with the support of crutches that included a push-button for step initiation Our results demonstrate that an exoskeleton with modular hardware and control allows SCI individuals with limited or no lower limb function to receive tailored support and regain mobility.

Neuromuscular Controller Embedded in a Powered Ankle Exoskeleton: Effects on Gait, Clinical Features and Subjective Perspective of Incomplete Spinal Cord Injured Subjects.

Powered exoskeletons are among the emerging technologies claiming to assist functional ambulation. The potential to adapt robotic assistance based on specific motor abilities of incomplete spinal cord injury (iSCI) subjects, is crucial to optimize Human-Robot Interaction (HRI). Achilles, an autonomous wearable robot able to assist ankle during walking, was developed for iSCI subjects and utilizes a NeuroMuscular Controller (NMC). NMC can be used to adapt robotic assistance based on specific residual functional abilities of subjects. The main aim of this pilot study was to analyze the effects of the NMC-controlled Achilles, used as an assistive device, on chronic iSCI participants' performance, by assessing gait speed during 10-session training of robot-aided walking. Secondary aims were to assess training impact on participants' motion, clinical and functional features and to evaluate subjective perspective in terms of attitude towards technology, workload, usability and satisfaction. Results showed that 5 training sessions were necessary to significantly improve robot-aided gait speed on short paths and consequently to optimize HRI. Moreover, the training allowed participants who initially were not able to walk for 6 minutes, to improve gait endurance during Achilles-aided walking and to reduce perceived fatigue. Improvements were obtained also in gait speed during free walking, thus suggesting a potential rehabilitative impact, even if Achilles-aided walking was not faster than free walking. Participants' subjective evaluations indicated a positive experience.

Gait training with Achilles ankle exoskeleton in chronic incomplete spinal cord injury subjects.

Powered exoskeletons (EXOs) have emerged as potential devices for Spinal Cord Injury (SCI) to support the intervention of physical therapists during therapy (rehabilitation EXOs) as well as to assist lower limb motion during the daily life (assistive EXOs). Although the ankle is considered a key joint for gait restoration after SCI, very few ankle exoskeletons were developed and tested in incomplete SCI (iSCI) population. Among those, the Achilles ankle exoskeleton is the only one embedding a Controller inspired by the neuromuscular system (NeuroMuscular Controller, NMC). In a previous study we demonstrated that a period dedicated to train iSCI subjects in using the Achilles EXO as an assistive aid, improved robot-aided walking speed and surprisingly also generated a positive trend in free walking speed on long and short distances thus suggesting a possible unexpected rehabilitation effect. To further investigate this result, a case-control longitudinal study was conducted in the present work. The aim of this study was to test the hypothesis that Achilles-aided training could improve performance of free walking of chronic iSCI people more than conventional intensity-matched gait rehabilitation. Before and after conventional and robot-aided rehabilitation a number of variables were analyzed, including spatiotemporal parameters, joint kinematics, ground reaction forces, muscle force, spasticity and its related symptoms, balance and personal experience about the training. Results showed that only the NMC-controlled Achilles training allowed participants to significantly walk faster, with a longer step length and a reduced gait cycle time. A slight force and spasticity improvements were also experienced. In terms of subjects' personal experience, Achilles training was perceived more interesting and less physically demanding than conventional rehabilitation.

Walking Index for Spinal Cord Injury version II in acute spinal cord injury: reliability and reproducibility.

STUDY DESIGN: Administration of the walking index for SCI (WISCI) II is recommended to assess walking in spinal cord injury (SCI) patients. Determining the reliability and reproducibility of the WISCI II in acute SCI would be invaluable. OBJECTIVES: The objective of this study is to assess the reliability and reproducibility of the WISCI II in patients with traumatic, acute SCI. DESIGN: Test-retest analysis and calculation of reliability and smallest real difference (SRD). SETTING: SCI unit of a rehabilitation hospital. METHODS: Thirty-three patients, median age 44 years, median time since onset of SCI 40 days. Level: 20 cervical, 8 thoracic, 5 lumbar; ASIA (American Spinal Injury Association) impairment scale (AIS) grade: 32 D/1 C. Assessment of maximum WISCI II levels by two trained, blinded raters to evaluate interrater (IRR) and intrarater reliability. RESULTS: The intrarater reliability was 0.999 for therapists A and 0.979 for therapists B, for the maximum WISCI II level. The IRR for the maximum WISCI II score was 0.996 on day 1 and 0.975 on day 2. The SRD for the maximum WISCI II score was 1.147 for tetraplegics and 1.682 for paraplegics. These results suggest that a change of two WISCI II levels could be considered real. CONCLUSIONS: The WISCI II has high IRR and intrarater reliability and good reproducibility in the acute and subacute phase when administered by trained raters.

Balance training improves static stability and gait in chronic incomplete spinal cord injury subjects: a pilot study.

BACKGROUND: Walking is considered the most important goal after an incomplete spinal cord injury (SCI). Only recently it has been demonstrated that balance is a key factor of walking recovery, but no data on the efficacy of balance training in supporting walking function in SCI subjects are available. AIM: The object of the study was to determine the efficacy of visual biofeedback task-specific balance training (vBFB) in improving balance performance and gait in SCI subjects compared with conventional over-ground rehabilitation (Rehab). DESIGN: Open-case study with retrospective matched control. SETTING: Chronic SCI outpatients and healthy subjects (H). POPULATION: Twelve SCI subjects with ASIA impairment scale grade D-6 in the vBFB group (EXP) and 6 in the Rehab group (CTRL)-and 6 H. METHODS: Data from H were used as reference for physiological balance and gait parameters. CTRL and EXP groups underwent 8 weeks of rehabilitation 5 times/week (CTRL group: 60 minutes devoted to Rehab; EXP group: 40 minutes of Rehab plus 20 of vBFB). At baseline (T0), every 10 vBFB sessions (T1-T2-T3), at the end of training (T4) and 1 and 2 months after vBFB was halted, data on the following parameters were collected and compared between groups and training steps: Berg Balance Scale, Walking Index for Spinal Cord Injury, 6-minute walking, 10-meter walk and timed up and go tests, balance performance (assessed with a stabilometric platform), and kinematic spatio-temporal gait parameters (collected using a 2-dimensional motion analysis system). RESULTS: At T4, only the EXP group experienced a significant improvement in balance and gait demonstrated by clinical and instrumental evaluation; the improvement was maintained at follow-up examinations. Further, in the EXP group, the enhancement in balance that existed at T1 preceded the improvement in gait, and significant correlations between the improvements in gait and balance were observed. In comparison with H data, vBFB treatment demonstrated a significant higher level of effectiveness than conventional Rehab. CONCLUSION: vBFB training is effective in improving balance and gait in chronic SCI subjects. CLINICAL REHABILITATION IMPACT: Inclusion of vBFB in rehabilitation protocols for chronic SCI subjects effects greater improvements in gait than conventional rehabilitation alone.

Distribution-based estimates of clinically significant changes in the International Standards for Neurological Classification of Spinal Cord Injury motor and sensory scores.

BACKGROUND: Although the psychometric properties and statistical significance of the International Standards for Neurological Classification of Spinal Cord Injury Patients (ISNCSCI) have been widely examined, the clinical significance of motor and sensory scores (i.e., the improvement in score that has a meaningful impact on patients) is unknown. AIM: To calculate the clinical significance of the International Standards for Neurological Classification of Spinal Cord Injury Patients (ISNCSCI). DESIGN: Analysis of prospectively collected data. SETTING: Spinal Cord Unit of a rehabilitation hospital in the centre of Italy. PATIENTS AND METHODS: Analysis of the data of 600 patients with registration of the ISNCSCI Motor scores (total score and separately upper and lower extremity scores) and ISNCSCI Sensory scores. Clinical significance was calculated per several distribution-based approaches: minimal important differences, effect size-based estimates for small and substantial changes, standard error of measurement, and minimal detectable change. The calculated clinical significance was compared with improvements by the patients to determine the percentage of patients who achieved significant improvement. Furthermore, the functional status (as evaluated by the Spinal Cord Independence measure [SCIM III]) was studied in patients who achieved significant improvement compared to those who did not achieve them. RESULTS AND DISCUSSION: The results of the study showed that motor scores were more amenable to change than sensory scores. A 5-point change in motor score resulted in a clinically significant improvement of 0.2 standard deviation units, and an 11-point change in motor score was associated with an improvement of 0.5 standard deviation units. The percentages of patients with a significant improvement varied from 8 to 80% according to the level and severity of the lesion. In some AIS grade/level of lesion groups, patients who achieved clinical significant scores also showed a better functional status with significantly higher SCIM III scores than those who did not achieve clinical significant scores: the functional relevance of the ISNCSCI change is maximal for AIS C cervical and thoracic lesions, whereas it appears to be limited for AIS A cervical and thoracic lesions, and null for lumbar lesions of any kind. CONCLUSION: The results of the study provide information on the amount of motor and sensory scores that can be considered as true and clinical significant, as well as on the percentage of patients that achieve clinical significant improvements. Worthy to note, most groups of patients showed a statistically significant improvement of MS and SS between admission and discharge, but in some of the groups (for example thoracic AIS A patients), this improvement was limited to a very low percentage of patients. CLINICAL REHABILITATION IMPACT: Our results provide useful benchmarks for clinicians and researchers with which changes in patient ISNCSCI motor and sensory scores can be interpreted as true and clinically meaningful, thus allowing a clinical judgment on interventions based on patients' progress. The proportion of patients with clinically significant improvements may be a useful benchmark in clinical trials: an intervention should be considered to be effective not only if it produces a greater statistically significant improvement in neurological status than another intervention or the natural course of the lesion, but also if it effects an increase in the percentage of subjects who achieve a clinically significant improvement.

Consumer preference in ranking walking function utilizing the walking index for spinal cord injury II.

STUDY DESIGN: Blinded rank ordering. OBJECTIVE: To determine consumer preference in walking function utilizing the walking Index for spinal cord injury II (WISCI II) in individuals with spinal cord injury (SCI)from the Canada, the Italy and the United States of America. METHOD: In all, 42 consumers with incomplete SCI (25 cervical, 12 thoracic, 5 lumbar) from Canada (12/42), Italy (14/42) and the United States of America (16/42) ranked the 20 levels of the WISCI II scale by their individual preference for walking. Subjects were blinded to the original ranking of the WISCI II scale by clinical scientists. Photographs of each WISCI II level used in a previous pilot study were randomly shuffled and rank ordered. Percentile, conjoint/cluster and graphic analyses were performed. RESULTS: All three analyses illustrated consumer ranking followed a bimodal distribution. Ranking for two levels with physical assistance and two levels with a walker were bimodal with a difference of five to six ranks between consumer subgroups (quartile analysis). The larger cluster (N=20) showed preference for walking with assistance over the smaller cluster (N=12), whose preference was walking without assistance and more devices. In all, 64% (27/42) of consumers ranked WISCI II level with no devices or braces and 1 person assistance higher than multiple levels of the WISCI II requiring no assistance. These results were unexpected, as the hypothesis was that consumers would rank independent walking higher than walking with assistance. CONCLUSION: Consumer preference for walking function should be considered in addition to objective measures in designing SCI trials that use significant improvement in walking function as an outcome measure.

Validity and reliability of the 10-m walk test and the 6-min walk test in spinal cord injury patients.

STUDY DESIGN: The 10-m walk test (10MWT) and the 6-min walk test (6MWT) have been recommended for assessment of walking in spinal cord injury (SCI) patients. The study was designed on test-retest analysis of the 10MWT and 6MWT. OBJECTIVES: The objective of this study was to assess validity/reliability of different methods of performing the tests. SETTING: The study was set at an SCI unit of a rehabilitation hospital. PATIENTS AND METHODS: A total of 37 patients; whose median age was 58.5 years (interquartile range 40-66, full range 19-77); median time since onset of SCI was 24 months (interquartile range 16.25-70.5, full range 6-109). Non-traumatic etiology in 20 out of 37 patients; level: 12C, 14T and 11L; American Spinal Injury Association Impairment Scale grade: 35D/2C. Assessment with the 10MWT (with or without dynamic start) and the 6MWT (short or long track) by two blinded raters to evaluate inter/intra-rater reliabilities. RESULTS: The 10MWT was performed in a median of 19 s (25th-75th interquartile range 13-28) with the dynamic start and of 18.4 s (25th-75th interquartile range 12.6-29.9) with the static start (P=0.092). The correlation between the results of the two methods was between 0.98 and 0.99. The inter- and intra-rater reliabilities were between 0.95 and 0.99 for both the methods. The 6MWT showed significant differences according to the track length: patients walked a median of 226.7 m (25th-75th interquartile range 123.2-319) on the longer track and of 187.6 m (25th-75th interquartile range 69.7-240.6) on the short one (P<0.001). The correlation between the results of the two methods was between 0.91 and 0.93. The inter- and intra-rater reliabilities were between 0.98 and 0.99. CONCLUSION: The 10MWT shows high inter/intra-rater reliability and shows comparable results with both dynamic and static start. The different testing conditions of the 6MWT (track/turns) results in significant differences that need standardization for use in future trials.