Endplate and intervertebral disc injuries in acute and single level osteoporotic vertebral fractures: is there any association with the process of bone healing?

BACKGROUND: The endplate-intervertebral disc (IVD) complex is closely interrelated with the vertebral body (VB) in the structural integrity of the anterior spinal column, including biomechanical and biological functions. Endplate and IVD injuries are usually found in association with vertebral fractures (VFs); however, little is known about their relevance to the healing of osteoporotic VFs (OVFs). The first purpose of this study was to evaluate the incidence and occurrence pattern of endplate and IVD injuries associated with single- and acute-OVFs, and the second was to evaluate the influence of endplate and IVD injuries on the occurrence of delayed union. METHODS: Endplate and IVD injuries associated with single- and acute-OVFs were retrospectively evaluated using magnetic resonance imaging (MRI). Vertebrae of 168 patients were included in the study. The occurrence rate and type of endplate and IVD injuries were radiologically evaluated, and the association between endplate and IVD injuries was statistically analyzed. Vertebrae of 85 patients, who received conservative treatment for acute OVFs, were included in the study and classified into two groups, union and delayed union, at 6 months after injury. To identify factors predicting delayed union, uni- and multivariate statistical analyses were performed. Vertebral MRI signal alternation patterns and endplate and IVD injuries were included as candidate factors in the logistic model. RESULTS: In association with OVFs, endplate injuries were observed in 103 of the 168 vertebrae (61%), and IVDs lesions were observed in 101 of 168 OVFs (60%); the occurrence of both injuries was significantly associated. Although no significant association with endplate and IVD injuries was identified, multivariate analysis demonstrated that intravertebral signal alternation (focal high signal intensity) and posterior wall injury were independent risk factors that predicted delayed union. CONCLUSIONS: The results of this study showed that endplate and IVD injuries were found in approximately 60% of single and acute OVFs. These results suggest that fracture healing of OVFs would be mainly attributed to vertebral factors, including mechanical stress and metabolic status, among the three components of the anterior spinal column.