Mobility Skills With Exoskeletal-Assisted Walking in Persons With SCI: Results From a Three Center Randomized Clinical Trial

Abstract

Background: Clinical exoskeletal-assisted walking (EAW) programs for individuals with spinal cord injury (SCI) have been established, but many unknown variables remain. These include addressing staffing needs, determining the number of sessions needed to achieve a successful walking velocity milestone for ambulation, distinguishing potential achievement goals according to level of injury, and deciding the number of sessions participants need to perform in order to meet the Food and Drug Administration (FDA) criteria for personal use prescription in the home and community. The primary aim of this study was to determine the number of sessions necessary to achieve adequate EAW skills and velocity milestones, and the percentage of participants able to achieve these skills by 12 sessions and to determine the skill progression over the course of 36 sessions. Methods: A randomized clinical trial (RCT) was conducted across three sites, in persons with chronic (≥6 months) non-ambulatory SCI. Eligible participants were randomized (within site) to either the EAW arm first (Group 1), three times per week for 36 sessions, striving to be completed in 12 weeks or the usual activity arm (UA) first (Group 2), followed by a crossover to the other arm for both groups. The 10-meter walk test seconds (s) (10MWT), 6-min walk test meters (m) (6MWT), and the Timed-Up-and-Go (s) (TUG) were performed at 12, 24, and 36 sessions. To test walking performance in the exoskeletal devices, nominal velocities and distance milestones were chosen prior to study initiation, and were used for the 10MWT (≤ 40s), 6MWT (≥80m), and TUG (≤ 90s). All walking tests were performed with the exoskeletons. Results: A total of 50 participants completed 36 sessions of EAW training. At 12 sessions, 31 (62%), 35 (70%), and 36 (72%) participants achieved the 10MWT, 6MWT, and TUG milestones, respectively. By 36 sessions, 40 (80%), 41 (82%), and 42 (84%) achieved the 10MWT, 6MWT, and TUG criteria, respectively. Conclusions: It is feasible to train chronic non-ambulatory individuals with SCI in performance of EAW sufficiently to achieve reasonable mobility skill outcome milestones.

Keywords: 10MWT; 6MWT; Food and Drug Administration; TUG; exoskeletal-assisted walking; mobility walking tests.

Figure 1

Exoskeletons used in this study: (A) ReWalk (ReWalk Robotics, Inc. Marlborough, MA, USA) and (B) Ekso GT (Ekso Bionics, Richmond, CA, USA).

Figure 2

Results of average steps per session block (A) and by session (B) split by device. Both those using the ReWalk (r² = 0.0956, y = 27.90x+931.24) and Ekso (r² = 0.082, y = 16.62x+1267.96) took more steps during later sessions. Since the first 6 sessions were pilot sessions where the participants were introduced to the device, the linear regression models were performed with data from sessions 7 to 36. The Ekso users increased the number of steps per session by 6 to 12 sessions then plateaued, whereas, the ReWalk users initially had less steps per session, but progressively increased by 36 sessions.

Figure 3

Results of Walking Tests across 12, 24, and 36 sessions by (A) device and (B) neurological deficit. Neurological deficit: Com Tetra (Motor Complete Tetraplegia); Inc Tetra (Motor Incomplete Tetraplegia); Com Para (Motor Complete Paraplegia); and Inc Para (Motor Incomplete Paraplegia). The main effects for neurological deficit (ANOVA: 10MWT (F_{(3, 46)} = 2.568, p = 0.658), 6MWT (F_{(3, 46)} = 2.267, p = 0.0933), TUG (F_{(3, 46)} = 0.946, p = 0.4263)) were not significantly different, but the main effects for sessions and device (10MWT: p < 0.0001, 6MWT: p < 0.0001, TUG-12: p = 0.0006, TUG-24: p = 0.1299, TUG-36: p < 0.0001) were statistically significant for each walk test as shown.

Figure 4

The average best number of total steps in a session block by level of SCI by device. The mean ± standard error of the best number of total steps/sessions achieved during each 12-session block by Tetra (Tetraplegia), Para (Paraplegia) and by device (ReWalk, Ekso) are reported. The overall best number of steps in a single session is reported for 1–36. The number of steps significantly increased by session block, but no significant effects were found for combination of Tetra/Para and Device.

Figure 5

Relationship between the total steps and 10MWT velocity at 36 session by Device. At 36 sessions, participants using either device showed that with more steps taken there was an associated increase in 10MWT velocity. A significant relationship was noted for those who used the ReWalk (r² = 0.296, p = 0.0028) and a trend for those who used the Ekso (r² = 0.131; p = 0.0983).