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Osteogenic Protein-1 Overcomes the Inhibitory Effect of Nicotine on Posterolateral Lumbar Fusion

Study Design. An established rabbit posterolateral lumbar fusion model was used to evaluate the ability of osteogenic protein-1 to overcome the inhibitory effect of nicotine. Objective. To determine whether osteogenic protein-1 should be considered as a bone graft alternative for the patient who smokes. Summary of Background Data. Smoking interferes with the success of posterolateral lumbar fusion. This inhibitory effect has been attributed to nicotine and confirmed in a New Zealand white rabbit model. Osteoinductive protein-1 has been shown to induce posterolateral spine fusion reliably in the rabbit model. The effectiveness with which osteogenic protein-1 induces fusion in the presence of nicotine has not been studied previously. Methods. Single-level posterolateral intertransverse process fusions were performed at L5–L6 in 18 New Zealand white rabbits. Either autograft or osteogenic protein-1 was used as grafting material. Nicotine was administered via subcutaneous mini-osmotic pumps. The animals were killed 5 weeks after surgery, and the resulting fusion masses were studied. Results. Three rabbits (17%) were excluded because of complications. By manual palpation, two of the eight nicotine-exposed autograft rabbits (25%) and all of the nicotine-exposed osteogenic protein-1 rabbits (100%) were found to be fused.. These results correlated well with those obtained from biomechanical testing. Histologically, the fusion zones of the nicotine-exposed autograft rabbits were distinctly less mature than the fusion masses of the nicotine-exposed osteogenic protein-1 rabbits. Conclusion. Osteoinductive protein-1 was able to overcome the inhibitory effects of nicotine in a rabbit posterolateral spine fusion model, and to induce bony fusion reliably at 5 weeks.