INTERVERTEBRAL DISC RECONSTITUTION AFTER CHEMONUCLEOLYSIS WITH CHYMOPAPAIN IS DEPENDENT ON DOSAGE - AN EXPERIMENTAL-STUDY IN BEAGLE DOGS

Study Design. The current report describes a study in beagles in which the effects of intradiscal injection of three doses of chymopapain we re evaluated with respect to the reduction of disc width and reconstit ution of the nucleus pulposus. Objectives. To establish an intradiscal dose of chymopapain that would achieve optimal reduction in disc heig ht followed by maximum reconstitution of the nucleus pulposus. Summary of Background Data. Earlier reports of the efficacy of high and low d oses of chymopapain for chemonucleolysis have provided conflicting dat a, and a scientific basis for an appropriate dose is lacking. Methods. Four mature, female beagles were subjected to chemonucleolysis using three doses of chympopapain as Chymodiactin (31, 63 and 125 picokatals /disc) injected into the L2-C3, L1-L2, and L3-L4 discs. Disc widths we re monitored radiographically over 32 weeks. Proteoglycans were radiol abeled by intravenous injection with (Na2SO4)-S-35 (1 mCi/kg) 24 hours before sacrifice, and their specific activities (disintegrations per minute/mg proteoglycan), hydrodynamic size, and ability to aggregate d etermined. Results. Sixty-three picokatals of Chymodiactin produced op timal disc reconstitution after chemonucleolysis. A reduction in disc height of approximately 35% was evident within 1 month and this slowly returned to approximately 90% of the preinjection value after 32 week s. The nucleus pulposus contained approximately 75% of the proteoglyca n content of control tissues, and most of these formed aggregates with hyaluronan. Disc collagen levels remained relatively unaffected by tr eatment. Conclusions. This study demonstrates that an effective reduct ion in disc width compatible with later reconstitution pulposus can be achieved experimentally with an appropriate dose of chymopain. These data clearly indicate that an optimal dose of chymopapain for chemonuc leolysis in humans needs to be established.