A comparison of resorbable and metallic fixation in healing of calvarial bone grafts

The effects of a resorbable fixation plate composed of a polylactic acid-polyglycolic acid copolymer were compared with those of a metallic fixation plate of similar dimensions in an animal calvarial bone-graft healing model. Bilateral parietal bone grafts in 20 mature rabbits were fixed into position with a titanium mesh plate on one side and a polymer mesh plate on the other side. After 2, 6, 9, and 12 months, cross-sectional histology was used to compare osteotomy line healing, tissue response to the fixation material, and the amount of resorbable plate degradation. After 2 months, no changes in the dimensions of the resorbable plate were observed. The bone grafts fixed by both metal and polymer plates exhibited incomplete healing along the osteotomy lines. After 6 months, there was a 66 percent reduction in the dimensions of the resorbable plate and vertical shortening of screw length. Complete healing was seen along all osteotomy lines of both bone grafts. After 9 months, less than 1 percent of the resorbable mesh plate remained as a small film underneath a collagenous capsule. No polymer was seen within the confines of the screw holes. After 1 year, no evidence of polymer was seen either on the external cranial surface or within any of the screw holes. Bony union was observed across all osteotomy sites. The screw hole outlines persisted. The resorbable plate demonstrated fixation stability similar to that of metal with comparable osteotomy line healing. No adverse local inflammatory reactions were seen as the polymer composite progressed to complete degradation by 1 year.