Biomechanical analysis of canine intervertebral discs after chymopapain injection. A preliminary report.

With the renewed interest in using chymopapain (CP) as a chemonucleolytic agent for treatment of sciatica and low-back pain, the present study was undertaken to investigate the biomechanical property changes in canine lumbar discs after CP injections. The short-term (30- to 120-minute) in vitro effects of such an enzymatic agent appear to be the same as those of saline solution, causing increased disc heights, stiffness values, and creep rates. In the in vivo study, after three weeks, CP-injected discs had significant reductions in disc height and compressive stiffness, but the creep rate was increased substantially. However, at three months after injection, these biomechanical properties began to reverse and approached those of the uninjected controls. Buffer solution (cysteine and EDTA) was tried, but the sample size was too small to provide conclusive information. The results suggest that CP causes a disc to change its material property, but such effects appear to be time-related.