Positive effect on bone fusion by the combination of platelet-rich plasma and a gelatin β-tricalcium phosphate sponge: a study using a posterolateral fusion model of lumbar vertebrae in rats.

We developed a novel method for bone fusion by combining platelet-rich plasma (PRP) and a gelatin β-tricalcium phosphate (β-TCP) sponge. The PRP is an autologous concentration of platelets that includes several growth factors. The gelatin β-TCP sponge comprises gelatin and β-TCP, thus enabling the sustained release of growth factors and osteoconduction. To evaluate this method, we generated a posterolateral fusion model of lumbar vertebrae in rats and divided it into five groups by implanting the following materials between transverse processes of vertebrae, (1) the gelatin β-TCP sponge with PRP (PRP sponge), (2) the gelatin β-TCP sponge with platelet-poor plasma, (3) gelatin hydrogel with PRP, (4) autologous iliac bone (autograft), and (5) no material was implanted as a control. The assessment of bone fusion by a radiographic assessment, a biomechanical test, microcomputed tomography, and histological evaluations demonstrated that there were no significant differences between the PRP sponge and the autograft groups regarding the osteogenic effect. Subsequent examinations revealed that no significant differences existed between the PRP sponge and the autograft groups in either biomechanical stiffness or the bone volume over time; whereas the radiographic and histological composition underwent similar changes in the fusion process. These results indicate that the PRP sponge could, therefore, be potentially useful as an attractive and less invasive method for bone fusion.