Micro-computed tomography evaluation of trabecular bone structure on loaded mice tail vertebrae.

Study Design: A micro-computed tomography (CT) study of the trabecular bone structure on loaded mice tail vertebral bodies was conducted.

Objective: To depict and characterize changes in the trabecular bone structure of mice tail vertebral bodies after in vivo application of static compressive load.

Summary Of Background Data: Static compressive loading leads to significant structural changes in murine tail intervertebral discs, such as disorganization of the anulus fibrosus, increase in apoptosis, and associated loss of cellularity. Wolff's Law suggests that alterations in spinal loading will also influence the architecture of the adjacent vertebral bodies. Because of biomechanical and biologic interdependencies between the disc and vertebra, these tissues should be considered simultaneously when investigating the etiology of degenerative spinal conditions.

Methods: Mice tail discs between the ninth and 10th caudal vertebrae were compressed in vivo for 7 days with static axial loads using external fixators. Micro-CT scans of the vertebral bodies were performed at an isotropic resolution of 18 microm, to obtain trabecular bone structural parameters. Random effects models were used to evaluate statistical significance of these parameters in different compressed conditions.

Results: With loading, the connectivity density of the trabecular network increases significantly. After a period of in vivo recovery on load removal, the trabeculae become more rod-like; corresponding changes such as disorganization of the anulus fibrosus and loss of nuclear and inner-anular cellularity are also seen.

Conclusions: In vivo compressive loading leads to significant architectural changes within vertebral bodies. These observations may be helpful in understanding the pathologic processes and the chronology of degenerative spinal conditions.