Changes in Endplate Vascularity After an Outer Anulus Tear in the Sheep

Abstract

In 31 2-year-old sheep, a 5-mm deep cut was made parallel to the end plates in the left anterolateral anulus fibrosus of 3 randomly selected lumbar intervertebral discs. At 2 months, the area of the end plate occupied by blood vessels on the left (operated) side had increased significantly (P < 0.05) in the cranial end plate to 9.94%, and to 9.39% in the caudal and plate, compared with nonoperated values of 5.17% (cranial) and 5.87% (caudal). One year after opertion, these elevated values had diminished significantly (P < 0.05) to 7.92% (cranial) and 7.13% (caudal), and continued to decline progressively to 7.48% (cranial) and 6.88% (caudal) by 2 years. In contrast, no significant differences were found on the right (nonoperated) side of the discs. Thus, there was an early proliferation of vascular channels in the end plate in the vicinity of the experimental anular lesion, but not on the nonoperated side of the same disc. Thereafter, the end plate vascularity progressively diminished toward a normal level.