title: The effects of chemonucleolysis on the mechanical properties of the canine lumbar disc.
abstract: One hundred and twenty-two lumbar intervertebral discs from 43 mongrel dogs were used to study the effect of chemonucleolysis on the flexion, torsion, and lateral bending flexibilities of the disc. The dogs were killed 2, 4, 12, 26, and 52 weeks following injection with 0.1-0.15 ml of either crude collagenase, semipurified collagenase, or chymopapain. Controls consisted of saline-injected and uninjected discs. The bending and torsional properties of each disc were determined by applying incremental moments up to 0.8 Nm and measuring the resultant rotations 60 seconds after each load increment was applied. The discs were then sectioned for morphologic evaluation. Increases in disc flexibilities ranging from 1.4 to 5.8-fold were found 2 weeks after injection with all three enzymes. The largest increase was noted in flexion in discs injected with chymopapain. By 3 months, all lateral bending flexibilities had returned to control values. In general, however, flexion and torsion flexibilities did not return to control values 6 months following chemonucleolysis. The extent of the gross morphologic changes produced by each of the three enzyme preparations did not correlate with the acute increases in disc flexibilities. Chymopapain and semipurified collagenase had similar morphologic and mechanical effects. The temporary increases in flexibility appeared to be due to decreases in the overall compression, tensile and shear stiffness of the annulus caused by the enzymes.
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002917:Chymopapain / Q000494:pharmacology*; D004285:Dogs; D007403:Intervertebral Disc / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D008159:Lumbar Vertebrae; D003012:Microbial Collagenase / Q000494:pharmacology*; D009068:Movement / Q000187:drug effects*
chemical_list: D002917:Chymopapain; D003012:Microbial Collagenase