Stopping nicotine exposure before surgery - The effect on spinal fusion in a rabbit model

Study Design. A double-blind, prospective, randomized study using a validated rabbit model of intertransverse process fusion. Objectives. To determine the effect of stopping prolonged nicotine exposure on autogenous bone graft incorporation in a rabbit lumbar spinal fusion model. Summary of Background Data. There is a growing body of evidence that systemic nicotine impairs healing of spinal fusions and fractures. However, it remains to be; determined whether, if nicotine increases the nonunion rate of spinal fusion surgery, stopping nicotine exposure before surgery will negate this inhibitory effect. Methods. Forty-seven rabbits were divided into two experimental groups and one control group. The two experimental groups were exposed to systemic nicotine for 8 weeks. Nicotine exposure was stopped in one group 1 week before surgery; nicotine exposure was continued in the other group throughout the study. All rabbits underwent an L5-L6 intertransverse process fusion with autogenous iliac crest bone graft. All rabbits were killed 35 days after surgery. Forty rabbits completed the study and underwent radiographic, biomechanical, and histologic testing. Results. Fusion, as determined by a blinded examiner palpating the spine, occurred in 7 of 13 control rabbits, 4 of 13 rabbits that quit nicotine, and none of the 14 rabbits exposed to continuous nicotine. There was a statistically significant difference between the control and continuous nicotine (P = 0.0015) and between the discontinued nicotine and continuous nicotine groups (P = : 0.025). Biomechanical testing showed no significant differences between groups (P = 0.11). A blinded musculoskeletal pathologist was unable to detect a difference between groups based on histologic analysis. Conclusions. Chronic nicotine exposure was shown to decrease spinal fusion rates. Discontinuing nicotine before surgery improved fusion rates.