Impact of spino-pelvic and global spinal alignment on the risk of osteoporotic vertebral collapse

Introduction: Numerous studies have reported the risk factors of osteoporotic vertebral collapse. However, whether spino-pelvic and global spinal alignments are associated with the occurrence of osteoporotic vertebral collapse remains unclear. This study aimed to investigate the association between spino-pelvic and global spinal alignments and the occurrence of osteoporotic vertebral collapse. Methods: A total of 46 consecutive patients who underwent a nonoperative treatment for a single-level fresh osteoporotic thoracolumbar vertebral compression fracture (T10 to L3) were retrospectively reviewed. The parameters evaluated were the pelvic incidence, anterior deviation of the C7 plumb line, distance between the C7 plumb line and the center of the fractured vertebra, and kyphotic wedge angle of the fractured vertebra in a standing whole-spine radiograph at the beginning of the nonoperative treatment. As an outcome measure, the presence or absence of osteoporotic vertebral collapse was radiographically evaluated at the final follow-up. Multiple logistic regression analysis was used to determine significant risk factors of osteoporotic vertebral collapse. Results: The mean values for each parameter were as follows: pelvic incidence, 58.0 degrees; anterior deviation of the C7 plumb line, 3.0 cm; distance between the C7 plumb line and the center of the fractured vertebra, 5.7 cm; and kyphotic wedge angle of the fractured vertebra, 14.6 degrees. Multiple logistic regression analysis revealed that the distance between the C7 plumb line and center of the fractured vertebra was a significant risk factor of osteoporotic vertebral collapse (p = 0.012; odds ratio, 1.025). The anterior deviation of the C7 plumb line (p = 0.214), pelvic incidence (p = 0.728), and kyphotic wedge angle of the fractured vertebra (p = 0.07) did not affect the occurrence of osteoporotic vertebral collapse. Conclusions: A large distance between the C7 plumb line and center of the fractured vertebra was a significant risk factor of osteoporotic vertebral collapse. The distance approximately represents that of between gravity center of trunk cranial to the fractured vertebra and the fractured vertebra. Accordingly, the large distance may cause larger flexion moment to the fractured site, leading to stress concentration that results in insufficient bone healing.