REVERSING THE INHIBITORY EFFECT OF NICOTINE ON SPINAL-FUSION USING ANOSTEOINDUCTIVE PROTEIN EXTRACT

Study Design, The effect on spinal fusion of an osteoinductive bone pr otein extract in the presence of a known inhibitor of spinal fusion (s ystemic nicotine) was studied prospectively in an animal model of post erolateral lumbar fusion. Objectives. To evaluate the ability of a bov ine-derived osteoinductive bone protein extract to overcome the inhibi tory effect of nicotine in a rabbit Spine fusion model. Summary of Bac kground Data. Multiple studies have demonstrated the ability of a vari ety of osteoinductive growth factors to serve as a bone graft substitu te or lumbar spinal fusion under ''normal'' healing conditions. Method s. Forty-eight adult female New Zealand white rabbits underwent spine arthrodesis at L5-L6 while receiving systemic nicotine through a subcu taneous miniosmotic pump. Arthrodesis was performed using one of the f ollowing three graft materials: 1) autogenous iliac crest, 2) osteoind uctive bone protein delivered in an allogeneic demineralized bone matr ix/collagen carrier, or 3) osteoinductive bone protein delivered with autogenous iliac crest. Fusions were assessed by blinded manual palpat ion, radiography, and biomechanical testing. Results. Of the 44 rabbit s manually tested by blinded observers, all 14 in the osteoinductive b one protein plus autogenous iliac crest bone group had solid fusions ( 14 of 14), whereas the fusion rate was less in the osteoinductive bone protein plus demineralized bone matrix group (nine of 14, 64%; P = 0. 02), and there were no fusions in the autogenous iliac crest only grou p (0 of 16, 0%; P = 0.000001). The use of osteoinductive bone protein with autogenous bone produced stronger and stiffer fusions compared wi th those using autogenous bone alone or osteoinductive bone protein wi th allograft bone. Conclusions. Cigarette smoking and nicotine are inh ibitory factors in the healing of fractures and spine fusions. This st udy shows that the inhibitory effect of nicotine can be overcome with an osteoinductive bone growth factor in an animal model.