The effect of chymopapain treatment on the rabbit intervertebral disc was studied in vivo. Different doses of chymopapain (0.3 to 80pKunits/10μl) were injected into the intervertebral disc of 18 Japanese white rabbits. One week after injection, disc heights had decreased in the groups receiving 2.5 pKunits/10μl or more. Twelve weeks after injection, disc heights had recovered only in the group receiving 2.5pKunits/10μl. Histologically, only 2.5pKunits/10μl injected discs showed disc regeneration. The loss of safranin-O staining was observed in the groups injected with 5pKunits/10μl or more chymopapain, and a large defect in the bony end-plate was seen in the discs injected with over 20pKunits/10μl. It was concluded that disc regeneration depends upon the dose of injected chymopapain. Also clinically, more desirable results may be expected by control of the injection dose.
