Impact Of Stainless Steel Screws Coated With Bisphosphonates On Bone

AIM: To study the fixation of stainless steel screws coated with bisphosphonate and the status of bone formation surrounding them from theradiography ,biomechanics and histology in normal and osteoporotic rats.METHODS :①Thirty-two female rats with nearly same body weight(224g--257g,the average weight is 235g±1g)aredivided into four groups(group A,group B group C and group D at random.②group of C and D are made the model of osteoporotic rats(we use Dexamethasone acetate injection,0.1mg/100g,two times a week.),the group A and C are injected with the same dose normal saline.Modeling time for 8 weeks.③Preparation of stainless steel screws:The Path 1.7mm,length 3mm stainless steel screws,after treatment by chemical reagents,we use chemical coupling to make bisphosphonates to maximize the cover in the stainless steel screw up.④Rats are anesthetized by 10% chloral hydrate ,we implant stainless steel screw in the middle of the right femur,group B,group D implant an ordinary stainless steel screws;group A,group C implant the stainless steel screws coating with bisphosphonate . After operation the right femur are taken X-ray film.⑤All the rats are killed by narcotic overdose 8 weeks later. Then,remove the screws,and take the X film the second time.The bone surrrounding the screws biopsy for histology.⑥Through the imaging observa- tion,biopsy,tartrate-resistant acid phosphatase staining (TRAP), under a microscope,record the width of fiber absorption membrane and the number of tartrate-resistant acid phosphatase-positive staining osteoclasts,then analyzed by statistics.RESULTS:Radiography shows that there are no obvious changes after operation. After eight weeks, remove the screw,the normal group shows around screw appear obvious low-density region, nail holes clearly visible, no obvious callus formation and the cortical bone around the screw become thinner .The treatment group shows callus formation around the bone screw obvious, screw-hole is not clear and the cortical bone around the screw become obvious thickening. On histologic observation , the width of the fiber membrane and the number of artrate-resistant acid phosphatase positive cells have a statistically significant decrease in the bisphosphonate coating groups than those in the normal group.CONCLUSION:No matter normal or osteoporosis rats, stainless steel screws coated with bisphosphonate can strengthen the fixation and inhibit bone resorption.