Posterolateral and anterior interbody spinal fusion models in the sheep

Posterolateral and anterior interbody spinal arthrodesis is a frequent proc edure. but high nonunion rates are reported and harvesting autologous bone graft from the iliac crest significantly increases morbidity, Bone graft su bstitutes are an alternative, but to date clinical results are not conclusi ve, Bone substitutes can be organic or inorganic, biologic or synthetic. Th ey can have osteoconductive properties, inductive properties or both. Anima l experiments are essential to investigating bone substitutes using biomech anical and histologic methods not available in clinical studies. Few author s reported on instrumented anterior fusion models, but none used the sheep model. In the current study posterolateral and anterior interbody fusion mo dels in sheep are described. Both models used instrumented fusions, applyin g porous mineral scaffolds, alone or mixed with bone. The surgical techniqu es are described step-by-step and potential difficulties are highlighted. P reliminary results are reported for the posterolateral fusion model using c oralline graft substitutes. The coral granules mixed with locally harvested bone had fusion outcomes similar to pure autologous bone, The graft substi tute showed marked resorption between 12 and 20 weeks, All fusions had bone cortex and good trabecular connectivity. Histologic evaluation suggests af ter 20 weeks nearly the entire surface of the substitute is covered with ne w bone, Porous mineral bone substitutes mixed with locally harvested autolo gous bone are thought to be a valid alternative for posterolateral fusions.