Augment Bone Graft Products Compare Favorably With Autologous Bone Graft in an Ovine Model of Lumbar Interbody Spine Fusion

Study Design. This study was designed to determine whether Augment Bone Graft (Augment, Biomimetic Therapeutics, Inc., Franklin, TN) and Augment Injectable Bone Graft (Augment Injectable, Biomimetic Therapeutics, Inc., Franklin, TN), 2 combination devices comprising recombinant human platelet-derived growth factor-BB and &bgr;-tricalcium phosphate–containing matrices, promote bone bridging in an ovine model of lumbar spine fusion. Autologous bone graft (autograft) was used as a positive control. Objective. The purpose of this study was to determine the ability of Augment products to promote fusion of the L2–L3 and L4–L5 vertebral bodies in an ovine model. Summary of Background Data. In interbody spine fusion, the intervertebral disc is removed and a spacer is inserted for support and to facilitate bone growth. The fusion is commonly enhanced with grafts. Autograft is the “gold standard” but it has limitations including availability and donor-site morbidity. Synthetic graft substitutes eliminate these complications. Augment products are combination devices including recombinant human platelet-derived growth factor-BB, a well-characterized chemotactic, mitogenic, and proangiogenic protein essential in wound and bone healing. Methods. Twenty-two sheep received an uninstrumented, double-level, interbody lumbar spinal fusion procedure using a polyetheretherketone spacer, which was either empty or packed with iliac crest autograft, Augment or Augment Injectable. The same treatment was used at both levels. Animals were 24 weeks after surgery, and fusion was assessed by micro-computed tomography (micro-CT) and histology. Results. Micro-CT and histologic assessment of fusion revealed that empty controls had significantly lower fusion rates. No differences were detected among autografts, Augment, and Augment Injectable–treated specimens. Residual &bgr;-tricalcium phosphate particles embedded in the newly formed bone were visible in Augment- and Augment Injectable–treated specimens. Conclusion. Augment-treated specimens had the highest fusion scores. Treatment with either of the Augment products significantly promoted interbody spine fusion compared with empty spacers and was equivalent to autograft-induced fusion. No adverse events were noted.