Relationship Between Muscle Mass of the Lower Limbs and Falls Caused by Spinal Misalignment in Women Aged 70 Years: A Retrospective Study

Study design: This retrospective study was conducted from 2015 to 2016 at the osteoporosis outpatient clinic of Showa University School of Medicine.

Objective: This study aimed to investigate the association between lower-limb muscle mass and spinal misalignment-related falls in elderly women.

Summary of background data: Poor spinal alignment affects gait and balance, reducing the quality of life. Negative correlations between age-associated skeletal muscle loss and spinal sagittal alignment have been reported.

Materials and methods: This study included 127 women with osteoporosis aged more than 70 years. The correlation between lower-limb skeletal muscle index (SMI) and sagittal vertical axis (SVA) was calculated using radiographic measurements. Spinopelvic parameters, including SVA, sacral slope, pelvic tilt (PT), pelvic incidence, and lumbar lordosis, were measured. Lower-limb SMI was measured using whole-body dual-energy x-ray absorptiometry and calculated as SMI=nonfat mass/height2. The balance function was evaluated using the single-leg stance test. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests; significance level was set at P<0.05. Bivariate and multivariate logistic regression analyses were used to determine correlations.

Results: Participants were classified into the balance and mismatch groups on the basis of a threshold SVA value of 50 mm. The groups did not differ significantly in age, height, weight, pelvic incidence, or sacral slope. Lumbar lordosis significantly decreased and PT and lower-limb SMI significantly increased in the mismatch group compared with the balance group. Lower-limb SMI was significantly correlated with increased SVA in bivariate and multivariate regression analyses. Patients with PT ≥20 degrees and SVA ≥50 mm had significantly increased lower-limb SMI.

Conclusions: Increased SVA is associated with increased lower-limb SMI, which negatively affects standing balance. An increased lower-limb SMI may represent a novel compensatory mechanism for poor spinal alignment in elderly women with osteoporosis.

Level of evidence: Level III.