Effects of collagenase upon the intervertebral disc in monkeys

The authors studied 5 rhesus monkeys for the effects of annulotomy, with or without the addition of a bacterially-derived collagenase into the nuclear-evacuated centrum of lumbar intervertebral discs. The animals were sacrificed from 3 weeks to 21 months after the single or staged double procedures. The earliest radiographic changes were loss of height of the interspace at 7 days, erosion of the vertebral body margins at 3 weeks, malalignment at 6 weeks, osteophytic formation at 3 1/2 months, sclerosis of vertebral body surfaces at 9 1/2 months, and fusion of adjacent vertebral bodies at 13 1/2 months. Pathological changes included early loss of disc convexity, focal new home formation, osteophytic new growth, through-and-through bone formation, irregular cystification, and disc replacement by hyaline fibrous tissue. Changes were reminiscent of those seen in humans with naturally acquired disc disease or aging of the disc. Injuries were produced in a tissue that probably has a limited scope of variation in reaction to insult.