Diaphyseal fractures treated by polylactide and hydroxyapatite pins. Experimental study in rat

In order to develop a biodegradable interlocking nail for fracture fixation, polylactic acid (PLA) pins and hydoxyapatite pins were implanted in the femoral bone in rats. A distal fracture was performed. The union and the tissue reaction to PLA and hydroxyapatite versus stainless steel rods were studied after 15 days, 1, 2 and 6 months implantation. Metal and PLA pins induced a union. Hydroxyapatite pins (Ossatite) did not prevent callus formation, but did not lead to consolidation in all cases because of weakness of the gelatin matrix binding the apatite particles together. PLA and stainless steel pins induced the same union and a similar tissue reaction during the studied implantation of 6 months. The biocompatility of Ossatite is satisfactory and the osteo-inductive properties of hydroxyapatite was confirmed. With injectable Ossatite, we could not obtain rat femoral fracture consolidation. We can confirm good biomaterial tolerance in bone which contrasts with important soft tissue reactions. Use of such material should be carefully limited to filling intra-osseous cavities.