仙骨筋の剛性測定におけるせん断波エラストグラフィーと閉経後女性の椎体骨折（VF）との関連：横断研究

Vertebral fracture (VF) is a significant public health issue that frequently occurs in postmenopausal women, leading to a decrease in quality of life and an increase in healthcare costs. Therefore, it is important to identify factors associated with VF. Even with high bone mineral density (BMD), VF can still occur, indicating that non-bone factors also play a significant role. Therefore, investigating the relationship between the trunk muscles involved in spinal stabilization and balance and VF is important for preventing VF. The aim of this study is to investigate the relationship between the stiffness of trunk muscles measured by elastography and VF in postmenopausal women over 60 years of age, controlling for the potential confounding effect of BMD.

This cross-sectional study included 81 women who visited the outpatient clinic between November 2024 and January 2025. Participants included those with VF (n = 41) and those without VF (n = 40). The group with VF was divided into two groups: those with osteopenia (n = 19) and those with osteoporosis (n = 22). Analyses were then performed on these three groups. The stiffness of the rectus abdominis (RA), obliquus externus (OE), obliquus internus (OI), transversus abdominis (TA), multifidus (MF), and erector spinae (ES) muscles of all participants was evaluated by calculating the Young's modulus using shear wave elastography. Functional assessment included the Berg Balance Scale (BBS), Time Up Go test (TUG), Functional Reaching Test (FRT), and QUELLEFFO-41.

There were no differences between groups in terms of demographic data, age, and body mass index (p > 0.05). No significant differences were found between groups in terms of the stiffness of the RA, OE, OI, and TA muscles (p > 0.05). In the analysis controlling for the covariate effect of BMD, there was a significant difference between groups in the stiffness values of the MF and ES muscles (p < 0.05); it was lower in the osteopenic group with VF than in the group without VF. There was a significant difference between the groups in the FRT (p < 0.05); it was highest in the group without VF and similar in the other two groups. There was no difference between the groups in terms of BBS, TUG, and QUALLEFFO-41 (p > 0.05).

In this study, the stiffness of the multifidus and erector spinae muscles was found to be lower in the osteopenic group with VF compared to the group without VF, after adjustment for the covariate effect of BMD. This finding suggests that trunk muscle stiffness is associated with VF in postmenopausal osteopenic women, after adjustment for lumbar spine BMD. Furthermore, the higher level of functional reach test in the group without VF suggests that paraspinal muscle stiffness may be related to trunk balance and reach function.