Effects of Active Spinal Orthosis on Fatty Infiltration in Paraspinal Muscles in Kyphotic Women with Osteoporotic Vertebral Fracture—Sub-Analysis of a Randomized Controlled Trial

<b>Background/Objectives</b>: Fatty infiltration of muscle is a predictor of degeneration. The present study determined the effect of an active spinal orthosis on muscle quality as determined by fatty infiltration in paraspinal muscles in older women with vertebral fractures and kyphosis. <b>Methods</b>: Twenty-one community-dwelling women ≥65 years with chronic back pain and vertebral fractures ≥3 months were randomly allocated to a group which wore the Spinomed active orthoses 2 × 2-3 h/d for 16 weeks (SOG: <i>n</i> = 11) or an untreated control group (CG: <i>n</i> = 10). Outcomes of the present study were parameters related to fatty infiltration of the musculi erector spinae and psoas major as determined by Magnetic Resonance Imaging (MRI). We applied a per protocol analysis; data were consistently adjusted for baseline values applying an ANCOVA. <b>Results</b>: Despite positive trends for all MRI parameters, no significant effects of the active spinal orthosis on fat infiltration of the musculus erector spinae were observed. Significant positive effects were, however, determined for musculus psoas major intra-fascial volume (<i>p</i> = 0.021; d': 1.18) and muscle tissue volume (<i>p</i> = 0.001; d': 1.80). No further significant effects on m. psoas major intra-fascial or muscle tissue average fat fraction or m. psoas major intramuscular adipose tissue volume were assessed. Of importance, no changes in variables that might have confounded the present result were reported. <b>Conclusions</b>: In line with recent exercise studies, the present high-volume, low-intensity back-strengthening intervention, induced by an active spinal orthosis, failed to generate significant effects on MRI measures of the m. erector spinae. On the other hand, significant effects on m. psoas major hypertrophy, albeit not fatty muscle infiltration, were determined. This new and unexpected finding should be confirmed by future studies.