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 inhibi tory effect of nicotine. Objective. To determine whether osteogenic protein-1 should be considered a s a bone graft alternative for the patient who smokes. Summary of Background Data. Smoking interferes with the success of posterol ateral lumbar fusion. This inhibitory effect has been attributed to nicotin e and confirmed in a New Zealand white rabbit model. Osteoinductive protein -1 has been shown to induce posterolateral spine fusion reliably in the rab bit 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 p erformed at L5-L6 in 18 New Zealand white rabbits. Either autograft or oste ogenic protein-1 was used as grafting material. Nicotine was administered v ia subcutaneous mini-osmotic pumps. The animals were killed 5 weeks after s urgery, and the resulting fusion masses were studied. Results. Three rabbits (17%) were excluded because of complications. By man ual palpation, two of the eight nicotine-exposed autograft rabbits (25%) an d all of the nicotine-exposed osteogenic protein-1 rabbits (100%) were foun d to be fused. These results correlated well with those obtained from biome chanical 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 ef fects of nicotine in a rabbit posterolateral spine fusion model, and to ind uce bony fusion reliably at 5 weeks.