Different Dose Nicotine Affect Posterolateral Lumbar Spinal Fusion: An Experimental Study In Rabbit Model

Purpose: To evaluate nicotine effect on rabbit model of integration.Toclarify the correlation between the dose of nicotine and spinal fusionrate.Methods:Select60healthy New Zealand white rabbits which months for sixto eight months.All rabbits were randomly divided into four groups, eachgroup have15rabbits.Group1as control group;2,3,4group asexperimental group.Four groups of animals were cut through the posteriorL5-6bilateral transverse process posterolateral fusion (PLF) underpentobarbital sodium anesthesia.For group1(control group)，use themethod of subcutaneous injection to inject saline solution,1ml/kg/t,3times a day,after the operation.For group2,3,4(experimentalgroup),use the method of subcutaneous injection to inject nicotinerespectively,2mg/kg/t,4mg/kg/t,8mg/kg/t,3times a day,after theoperation.To kill rabbits with air embolism method after12weekspostoperatively.Intercept the spine specimen of L4-L7, using touchingexamination, X-ray, CT scan method to evaluate nicotine effect on rabbitmodel of integration.Finally,the specimens of fusion was made ofmechanics specimen with using self-curing denture acrylic,and then dobiomechanical testing experiment.Record the displacement and stresscurve after applying anteflexion loading in each specimen.Record themaximum stress when the specimen fracture.Through the comparison of theexperimental group and control group,and the comparison between differentdose of nicotine group,exploring the influence of the fusion rate afterthe injection of nicotine. Results: At12weeks after surgery， judge convergence rate thoughtouching method, group1fusion rate was73.3%, group2fusion rate was66.7%, the third group of the fusion rate was20.0%, the fourth group ofthe fusion rate was13.3%;judge convergence rate though X-ray, group1fusion rate was93.3%, group2fusion rate was86.7%, the third group ofthe fusion rate was26.7%, the fourth group of the fusion rate was20.0%;judge convergence rate though CT scan, group1fusion rate was80.0%,group2fusion rate was66.7%, the third group of the fusion rate was33.3%,the fourth group of the fusion rate was26.7%.Three methods to judge thefusion rate, the difference of fusion rate between group1and group2has no statistical significance (P>0.05).The difference of fusion ratebetween group1and group3,group1and group4has statisticalsignificance（P<0.05）.That has certain influence of rabbit spinal fusionwith the increase of nicotine dose.Biomechanical testing results showthat:①all of the experimental group, low dose or high doses of nicotinegroup compared with control group (normal saline group), the differencehad statistical significance (P <0.01).②the low dose group (group2)and middle dose group (group3) and high dose group (group4) the differencehad statistical significance (P <0.01).③medium dose group (group3)and high dose group (group4) the differences had no statisticalsignificance (P>0.05).Conclusions: Touching method and imaging evaluation proved that low dosesof nicotine had no obvious effect on spinal fusion, moderate dose and highdose of nicotine hindered the fusion of the spine.Though biomechanicsresearch shows that:all doses of nicotine had effect on lumbarposterolateral fusion, and with the increase of nicotine dose, spinalfusion rate dropped significantly.