Degenerative changes of porcine intervertebral disc induced by vertebral endplate injuries

Study Design. Graded endplate injuries were performed in porcine lumbar discs. The effects of such injuries were compared to control animals in which a sham operation was performed. Objectives. To investigate the effects of endplate injuries on disc tissue. Summary of Background Data. Studies have shown that injuries of vertebral endplates are frequently found at autopsy. However, little is known on the effects of acute injuries of vertebral endplates in vivo. Methods. Ten domestic pigs were included in the study group. Under general anesthesia, the lower three discs of the lumbar spine were exposed and randomly submitted to multiple endplate injuries, isolated endplate injury, and no treatment. A sham operation was performed in 5 pigs used as control group. Animals were killed 7 months after surgery and the harvested lumbar spine submitted to MRI investigations, histologic, and biochemical analysis. Results. MRI showed that all but one discs treated with multiple endplate injuries were markedly degenerated while, of the discs treated with an isolated injury, one was markedly degenerated, five slightly degenerated and two were normal (P=0.01). Histologic analysis showed severe changes in discs treated with multiple injuries. In those who had an isolated injury, changes were less severe and essentially limited to the posterior anulus or the inner anterior anulus. Biochemical analysis showed an inverse correlation between uronate content in the nucleus pulposus and severity of endplate injuries. Conclusions. Injuries of vertebral endplates in porcine discs were found to cause degenerative changes in the disc tissue on MRI, histologic, and biochemical investigations. The severity of such degenerative changes was related to the severity of endplate injuries. Injuries of vertebral endplate may be one of the pathomechanisms leading to early changes in the disc matrix and eventually to abnormal biomechanical behavior of the whole disc. The present animal model seems to be a suitable experimental model for disc degeneration.