Abstract

Study Design. This study was designed to determine whether Augment Bone Graft (Augment) and Augment Injectable Bone Graft (Augment Injectable), two combination devices comprised of human recombinant platelet-derived growth factor-BB (rhPDGF-BB) and β-tricalcium phosphate (TCP)-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 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 rhPDGF-BB, a well characterized chemotactic, mitogenic and pro-angiogenic protein essential in wound and bone healing.Methods. Twenty-two sheep received an un-instrumented, double-level, interbody lumbar spinal fusion procedure using a polyetheretherketone (PEEK) 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 euthanized 24 weeks after surgery and fusion was assessed by microCT and histolology.Results. MicroCT and histologic assessment of fusion revealed that empty controls had significantly lower fusion rates. No differences were detected among autograft, Augment and Augment Injectable-treated specimens. Residual β-TCP 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 to empty spacers and was equivalent to autograft-induced fusion. No adverse events were noted.