Variation Patterns and Correlation Between BTMs and Microparameters of Trabecular Bone and Macro－mechanical Strength of Lumbar Vertebrae

Summary: This 4-month study was conducted in 64 white rabbits.The correlation between the microstructure, micro-mechanical properties and macroscopic mechanical strength of BTMs, bone trabeculae was investigated. CTX-I showed the strongest correlation with microstructure and micromechanical properties, while OC showed the strongest correlation with macroscopic mechanical strength. Objective: To investigate the variation patterns and correlations among serum bone turnover markers (BTMs), microstructure of trabecular bone, micro-mechanical properties, and macro-mechanical strength during the process of osteoporosis, and to identify BTMs that show strong correlations with all three. Methods: A total of 64 female New Zealand white rabbits were randomly divided into a sham surgery group (Sham group, n=32) and an osteoporosis model group (OP group, n=32). Rabbits in both groups were further randomly assigned to baseline (Pre-ovx), and three subsequent groups at 1, 2, and 4 months (n=8 each). Bone mineral density (BMD) was measured at Pre-ovx, and 1, 2, and 4 months post-surgery. Serum BTMs were collected from arterial blood, and lumbar vertebrae specimens were obtained to measure the microstructure, micro-mechanical properties, and macro-mechanical strength of trabecular bone. Results: BMD, maximum load (L _max ), elastic modulus of trabecular bone, hardness, trabecular thickness (Tb.Th, mm), trabecular number (Tb.N, 1/mm), and bone volume fraction (BV/TV, %) gradually decreased, while trabecular space (Tb.Sp, mm), osteocalcin (OC), type I procollagen N-terminal propeptide (PⅠNP), and C-terminal telopeptide of type I collagen (CTX-I) gradually increased. Multiple linear regression showed that Tb.Th (β=0.369, P=0.038) and the elastic modulus of trabecular bone (β=0.594, P=0.002) were positively correlated with Lmax, while CTX-I was negatively correlated with both Tb.Th (β=-0.953, P=0.002) and the elastic modulus of trabecular bone (β=-0.963, P=0.000). OC was negatively correlated with L _max (β=-0.966, P=0.000). Conclusion: The elastic modulus of trabecular bone has the most significant impact on macro-mechanical strength. CTX-I showed the strongest correlation with microstructure and micromechanical properties, while OC showed the strongest correlation with macroscopic mechanical strength.