The degenerative response of rat tail
intervertebral discs to a stab incision was evaluated.
To examine and compare the postinjury degenerative response of lumbar
Summary of Background Data.
Although successful in larger animals, a stab incision for inducing disc degeneration
in rats has not been evaluated. Rodents are desirable models for disc repair studies due to their low cost, ease of care, and fast healing times.
discs were exposed surgically and stabbed with a number 11 blade. Disc architecture, levels of IL-1β, IL-6, and TNF-α, and biomechanical properties were analyzed. A functional disability secondary to multilevel lumbar
disc injury was quantified and compared with that of rats undergoing sham surgery.
Histologic evaluation of stabbed tail
discs demonstrated a nucleus pulposus size decrease, anular collagen layer disorganization, and cellular metaplasia of anular fibroblasts to chondrocyte-appearing cells. Besides the continued presence of the stab injury tract, few changes were observed in the lumbar
disc histology. Cytokine measurements indicated a transient peak in IL-1β in tail
discs 4 days following injury. No significant changes in IL-1β, IL-6, or TNF-α were measured. No significant differences in biomechanical properties were observed between stab injury and sham surgery discs. Yet, despite insignificant differences in histologic, cytochemical, or biomechanical properties in the lumbar
discs, the rats with lumbar
stab injury had a significant decrease in walking ability 28 days after surgery.
disc stab injury was successful in creating morphologic signs of degeneration
and transient high concentrations of IL-1β. However, the degenerative response in the lumbar
discs was much slower, suggesting that site-specific factors, such as increased stability due to posterior elements and torso musculature, helped facilitate healing. Yet, functional assessment indicated that the rats were partially disabled by multiple lumbar