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A Quantitative Model of Post-laminectomy Scar Formation: Effects of a Nonsteroidal Anti-inflammatory Drug

Study Design. A quantitative model of peridural post-laminectomy fibrosis in rats was designed in this study. Concurrently, the effects of a nonsteroidal antiinflammatory drug (ketoprofen) were evaluated. Objectives To quantify the amount of fibrotic tissue, the extent of adhesion to the dura mater, and the cell nature and density for drug trials requiring large series of animals. Summary of Background Data Most of the previous analyses of experimental post-laminectomy fibrosis were qualitative in nature. Only one quantitative analysis was reported in the rabbit, and the rat has seldom been used. The effects of nonsteroidal anti-inflammatory drugs on post-laminectomy scar formation have never been evaluated. Methods L5 laminectomies were performed in 32 rats. The treated group (16 rats) received a systemic injection of ketoprofen (5 mg/kg, once daily from the day before the operation to the seventh postoperative day), the other 16 rats constituted a control group. The post-laminectomy scar formation was evaluated on postoperative days 8, 15, 30, and 90 using a semiautomatic image analysis system. Results The course of post-laminectomy scar formation was similar to that described in larger animals. There was a good correlation among the measurements of fibrous tissue area obtained by 2 independent observers. The mean amount of peridural scar tissue was significantly smaller in the treated group than in the control group. The extent of adherence to the dura mater and the density of fibroblasts and fibrocytes was not different between the two groups. The density of inflammatory cells was significantly less in the treated group than in the control group only at day 8. Conclusion Quantitative evaluation of post-laminectomy fibrosis can easily be performed in rats and is reproducible. This model could allow trials with drugs administered locally or systemically as preventive treatment of post-laminectomy scar formation. Nonsteroidal anti-inflammatory drugs could decrease the amount of fibrotic tissue.