JMIR Publications

ABSTRACT

Background:

As many as 60% of individuals use a wheelchair long-term after a spinal cord injury (SCI). This mode of locomotion leads to chronic decline in lower-extremity weight-bearing activities and contributes to the development of severe sublesional osteoporosis and high rates of fragility fracture. Overground exoskeleton-assisted walking programs provide a novel opportunity to increase lower-extremity weight-bearing, with the potential to improve bone health.

Objective:

To measure the potential effects of an exoskeleton assisted walking program on lower-extremity bone strength and bone remodeling biomarkers in individuals with chronic (≥18 months) SCI who use a wheelchair.

Methods:

Ten participants completed a 16-week exoskeleton assisted walking program (34 individualized 1-hour sessions, progressing from 1 to 3 per week). Bone mineral density and bone strength markers (Dual-energy X-ray absorptiometry, DEXA: total body, and left arm, leg, total hip and femoral neck; peripheral quantitative computed tomography, pQCT: 25% of left femur and 66% of left tibia), as well as bone remodeling biomarkers (formation = osteocalcin, resorption = c-telopeptide) were measured pre- and post-intervention and compared using nonparametric tests. Changes were considered significant and meaningful if the following criteria were met: p<0.1, effect size ≥0.5 and relative variation >5%.

Results:

Significant and meaningful increases were observed at the femur (femoral neck bone mineral content, bone strength index, stress-strain index) and tibia (cortical cross-sectional area, polar moment of inertia) after the intervention. We also noted a decrease in estimated femoral cortical thickness. However, no changes in bone remodeling biomarkers were found.

Conclusions:

These initial results suggest promising improvements in bone strength markers after a 16-week exoskeleton-assisted walking program in individuals with chronic SCI. Additional research with larger sample sizes, longer interventions (possibly of greater loading intensity), and with combined modalities (e.g., pharmacotherapy or functional electrical stimulation) are warranted to strengthen current evidence. Clinical Trial: U.S. National Library of Medicine (registration number NCT03989752) on June 7, 2019.