REPAIR OF REGIONAL OSTEOPOROSIS AFTER REMOVAL OF RIGID FIXING PLATE -AN EXPERIMENTAL INVESTIGATION

Twenty-four New Zealand white rabbits were plated on their intact left tibiae with stainless steel plates and 4 animals served as controls. The plates were removed 2 months after implantation in 20 plated anima ls. Of them, 4 were sacrificed immediately after plate removal and the other 16 were killed in successive groups with 4 in each group 1,2,3 and 4 months after plate removal respectively. The remaining 4 plated animals were killed at 6 months after implantation. Bone samples under the plates were harvested and prepared for polarized light microscopy to investigate the repair of the regional osteoporosis induced by rig id implant. The results indicated that the regional osteoporosis could recover gradually after plate removal. The repair process manifested itself mainly as the repair of resorption cavities and the remodeling of collagen fibers. The orientation of the collagen fibers remained di sorganized when the resorption cavities had been repaired. It is sugge sted that delayed restoration of bone structure might be one of the po tential causes of refracture after removal of the rigid implant.