Bone Response to a Novel Porous PLLA Scaffold

Objectives: The development of resorbable porous materials that encourage rapid bone growth under loading conditions may improve the options for surgical treatment of bone defects. A novel PLLA scaffold has been developed to enhance the mechanical condition effects due to its controlling release of calcium channel agonist, (BAY). We report a preliminary study to assess bone response to the scaffolds in vivo. Methods: PLLA scaffolds with 90% porosity and 250-350 µm pore size were produced and trimmed into blocks 3 x 2 x 1mm. Samples where collagen coated or incorporated with BAY and collagen coated. Male Wistar rats had either one implant placed into the right femur PLLA/collagen (n=3) or PLLA/collagen/BAY (n=3) or surgery without implant placement (n=3). Surgery was carried out under general anaesthesia using a standard technique. Animals were sacrificed at 5 weeks; the femurs were excised, fixed in formalin, decalcified and processed for routine H&E sections. Results: Two sham operated femurs had fractured and healed with callus formation, the other healed normally. One femur in each test group also fractured and was difficult to assess. The remaining femurs showed significant bone growth into the pores of the scaffold in both the cortex and medullary space. Where scaffold had not completely filled the medullary space there was no new bone. Macrophages and multinucleate giant cells were seen in association with scaffold material. From the limited samples it was not possible to determine if the incorporation of BAY significantly influenced bone formation but the scaffold itself was associated with increased bone formation. The presence of scaffold may have reduced the incidence of fracture in this load bearing site. Conclusions: Porous PLLA with collagen or collagen + BAY may enhance trabecular bone growth in this model.

Acknowledgments: EXPERTISSUES Network of Excellence (NoE)–NMP3-CT-2004-500283. EPSRC GR/S11510/01