Therapeutic Effects of Noninvasive Technology Modalities on Lower-Limb Motor Function in Spinal Cord Injury: A Systematic Review

Abstract

Objectives: To systematically evaluate the effects of noninvasive technology modalities, defined as externally applied stimulation or feedback devices, on lower-limb motor outcomes in individuals with spinal cord injury (SCI), addressing gaps in generalizability and classification to support evidence-based rehabilitation strategies.

Data sources: We systematically searched PubMed, Web of Science, EMBASE, and the Cochrane Library for English-language articles from database inception to 2023 (initial search conducted in April 2024 and updated in January 2025).

Study selection: We included randomized controlled trials involving adults with SCI that investigated noninvasive technology modalities applied to any body region and reported outcomes related to motor score, muscle performance, or walking ability. Of 2325 records screened, 22 full-text articles were independently evaluated by 2 reviewers, and 11 met the inclusion criteria and were included in the review.

Data extraction: Two reviewers independently extracted data from eligible studies, with disagreements resolved through consensus with a third reviewer. The risk of bias (RoB) was assessed using the Cochrane RoB 2 tool by 2 reviewers.

Data synthesis: Across the included studies (224 participants; mean age=44.9 y), interventions typically consisted of 30-minute sessions, 4 times weekly, over 6 weeks. Four studies applied transcranial stimulation, 4 used transspinal stimulation, and 3 targeted muscle stimulation. Outcomes were evaluated in 4 studies for motor score, 7 for muscle performance, and 7 for walking ability. Most interventions, combined with standard rehabilitation, showed improvements across these outcomes, although only a subset demonstrated statistically significant between-group effects. RoB was low in 6 studies, had some concerns in 3, and was high in 2.

Conclusions: Noninvasive modalities appear effective in enhancing lower-limb motor function in individuals with SCI. However, variability in intervention protocols and methodological quality limits the ability to draw definitive conclusions. Further studies should standardize protocols and minimize bias to strengthen the evidence for SCI rehabilitation strategies.

Keywords: Lower motor function; Noninvasive stimulation; Rehabilitation; Spinal cord injury; Systematic review; Transcranial direct current stimulation; Transcranial magnetic stimulation.

Fig 1

Flowchart of study identification based on the PRISMA statement.

Fig 2

RoB assessment across the included studies using the Cochrane RoB 2 tools. This figure summarizes the RoB assessments for the included studies, categorized into low risk, some concerns, or high risk, across 5 domains (D1-5). Results reflect the overall judgment of each study, with color-coded classifications (green: low risk, yellow: some concerns, red: high risk).