Ultrastructural study on effects of swan-like memory compressive connector on bone healing

Objective:To explore the effect and mechanism of swan like memory compressive connector(SMC) made of Ni Ti shape memory alloy on experimental fracture healing. Methods:A transverse osteotomy on both sides of femoral diaphyses was performed in 25 adult dogs. One side was plated with compression plate(CP) and the other with SMC. Five animals in each group were sacrificed at 1,2,4,8,12 weeks after operation and observed with X ray examination, light microscopy and transmission electron microscopy. Results:In SMC group, the process of fracture healing was accelerated with SMC fixation, and no external callus and osteoporosis were observed. A great number of osteoblasts and chondroblasts with high functional activity emerged 2 4 weeks after operation. While in CP group, the number and functional activity of osteoblasts and chondroblasts were lower than those of SMC group. By 8 weeks after operation, the lamellar bone substituted the woven bone. The osseous callus bridged the fragments of fracture, but the bony absorbed cavities and osteocyte entered into degenerative phase were observed in cortical bone underneath CP. A small number of bony absorbed cavities were formed underneath SMC 12 weeks post operation, the bony absorption cavities underneath CP were enlarged remarkably. Conclusion:Fixation with SMC is stable, and it can provide continual axial stress for fracture fragment, which enhances fracture healing and bone reconstruction.