Relationship between Health-Related Quality of Life and Sagittal Whole-Body Alignment, Standing Balance, and Skeletal Muscle Mass.

Introduction: Impaired standing alignment and postural instability diminish health-related quality of life (HRQOL). Reduced trunk muscle mass is correlated with worsened spinal alignment and HRQOL in patients with spinal disease. However, the interplay among standing balance, whole-body alignment, muscle mass, and HRQOL remains unclear. This study aimed to elucidate this relationship. Methods: This study evaluated the influence of whole-body alignment, standing balance, skeletal muscle mass (SMM), aging, and sex on HRQOL in healthy volunteers (HV; men/women: 37/63, median age: 45), patients with lumbar degeneration (LD; men/women: 100/100, median age: 65), and patients with spinal deformity (SD; men/women: 16/84, median age: 71). HRQOL was assessed using the Scoliosis Research Society-22 (SRS-22r). Whole-body alignment and standing balance were measured using EOS Imaging combined with simultaneous force plate measurements. SMM was measured using a medical body composition analyzer. Based on univariate analysis and multicollinearity, 10 selected parameters were used in multivariate logistic regression analysis to identify factors affecting SRS-22r. Results: The SRS-22r score was significantly higher in the HV group than in the LD and SD groups; however, there were no significant differences between men and women. The whole-body alignment and standing balance were better in the HV group, followed by the LD and SD groups. The total-body SMM (SMM.total) of men was significantly lower in the LD and SD groups than in the HV group. In females, the SMM.total was significantly lower in the SD group than in the HV and LD groups. However, trunk SMM did not significantly differ among the three groups. Based on the multivariate analyses, diagnosis, body mass index (BMI), SMM.total, lumbar lordosis (LL), and T1 pelvic angle (TPA) were correlated with the SRS-22r score. Conclusions: HRQOL was negatively affected by spinal disease, as well as by higher BMI, lower SMM.total, and sagittal malalignment (smaller LL and greater TPA).