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

Study Design. A double-blind, prospective, randomized study using a validat ed 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 mo del. Summary of Background Data. There is a growing body of evidence that system ic nicotine impairs healing of spinal fusions and fractures. However, it re mains to be; determined whether, if nicotine increases the nonunion rate of spinal fusion surgery, stopping nicotine exposure before surgery will nega te 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 nic otine 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 su rgery. Forty rabbits completed the study and underwent radiographic, biomec hanical, and histologic testing. Results. Fusion, as determined by a blinded examiner palpating the spine, o ccurred in 7 of 13 control rabbits, 4 of 13 rabbits that "quit" nicotine, a nd none of the 14 rabbits exposed to continuous nicotine. There was a stati stically 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 differen ces between groups (P = 0.11). A blinded musculoskeletal pathologist was un able 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.