Acute Increase in Lateral Bending of the Canine Lumbar Disc Following Chymopapain Injection

Abstract

Twenty-four lumbar discs in six adult beagle dogs were injected with either 0.1 ml CP (ChymodiactinR) (200 U) (12 discs) or 0.1 ml saline (12 discs) under direct vision at laparotomy. All animals were killed 1 hour later; the lumbar spine was immediately excised en bloc and frozen until biomechanical testing. After overnight thawing, test specimens were prepared and consisted of a disc and half a vertebral body on each side. The posterior elements were discarded. Each motion segment was mounted on a testing plate, with bone cement used for fixation. Lateral bending of the motion segment was tested as an analog to the motion of a disc during correction of a scoliotic spine with a distraction force. Lateral bending forces of 2 kg and 4 kg were applied for 30 minutes each. Lateral bending, creep, and residual deformity (in degrees) were recorded. CP injected disc showed an acute increase in lateral bending of 28% and 26%, respectively (2-kg and 4-kg loads) (P less than 0.001). In addition, CP injected discs showed a 25% increase in their residual angular deformity compared with the control discs (P less than 0.001). No significant changes were noted in creep values between CP and saline injected discs. This study demonstrates a significant acute increase of 28% and 26% in lateral bending of the canine disc following enzyme injection.