Effective atomic number of paraspinal muscles is associated with acute vertebral fracture risk.

ABSTRACT

OBJECTIVES: To investigate the relations among effective atomic number (Zeff), density, and area of paraspinal muscles, volumetric BMD (vBMD), and acute vertebral fractures (VF) by using spectral base images (SBIs) and routine CT images. METHODS: A total of 223 patients (52 men and 171 women) with acute VF and seven hundred and seventy-six subjects (286 men and 390 women) without VF of at least 60 years were enrolled and underwent dual-layer detector CT scans. We quantified the cross-sectional area (paraSMA), density (paraSMD) and Zeff of paraspinal muscles by CT images and SBIs and measured vBMD of the lumbar spine by quantitative CT. RESULTS: Higher vBMD was associated with lower VF risk in both sexes (adjusted OR, 0.33 and 0.43). After adjusting for age and BMI, the associations of ParaSMD with VF were not significant in men, and in women the association was borderline significant (OR, 0.80; 95% CI, 0.64 to 1.00). However, higher Zeff of paraspinal muscles was associated with lower VF risk in men (adjusted OR, 0.59; 0.36 to 0.96) but not in women. The associations of all muscle indexes with VF were not significant after further adjusting for vBMD. CONCLUSIONS: A higher Zeff of paraspinal muscles is associated with lower VF risk in older men but not in older women. The density, area and Zeff of paraspinal muscles were not vBMD independent risk factors for acute VF. ADVANCES IN KNOWLEDGE The effective atomic number of paraspinal muscles might be a potential marker for vertebral fracture risk prediction.