rhBMP-2 in an injectable Gelfoam carrier enhances consolidation of the distracted callus in a sheep model

BACKGROUND: A major problem associated with distraction osteogenesis is the long time required for consolidation. OBJECTIVE: The goal of this study was to determine whether a percutaneous injection of recombinant human bone morphogenetic protein-2 (rhBMP-2) in a Gelfoam carrier would enhance bone consolidation following distraction. METHODS: A unilateral tibial osteotomy combined with external stabilization was performed in 14 adult sheep. After a latency of four days, distraction was performed at 1.25 millimetres per day for 20 days. On days 23 and 30, the sheep received an injection of rhBMP-2/Gelfoam or buffer/Gelfoam. During the following 50 days, radiographs and in vivo torsional stiffness measurements were obtained weekly. The effect of rhBMP-2 treatment post-mortem was assessed using destructive biomechanical testing, quantitative CT and DXA analysis. RESULTS: The in vivo stiffness measurements of the sheep treated with rhBMP-2 were significantly higher than those of the carrier control group (p< 0.05). These in vivo data were verified by post-mortem biomechanical testing and quantitative CT analysis. The maximum torsional moment observed was 55% greater in the sheep treated with rhBMP-2. CONCLUSIONS: These data support the potential use of rhBMP-2 in an injectable carrier for enhancing consolidation, as it may ultimately lead to shorter treatment times for patients undergoing distraction procedures.