Study On The Assessment Of Synchrotron Radiation Contrast CT Imaging In Tibial Fracture Healing In Kunming Mice

Objective1.To explore the feasibility of synchrotron radiation phase contrast CT imaging in detecting multi-stage morphological and structural changes tibial fracture healing in mice.2.To explore the different expression of II collagen(Col II),X collagen(Col X)and osteocalcin(Osteocalcin)in the process of tibial fracture healing in mice,and to compare and analyze the correlation between them with the imaging of multi-stage synchronous radiation CT fracture healing process.Material and MethodsTwenty-five 6-week-old Kunming male mice were randomly divided into five groups: A、B、C、D and E,Five in each group.All mice were treated with artificial fractures to the right tibia,Fixed with self-made external fixator.The right tibia was extracted 5,10,15,21 and 28 days after operation.Fixed with 4% formaldehyde for 12 hours.These samples dried naturally,then imaged with synchrotron radiation phase contrast CT.These imaged samples were decalcified with EDTA disodium.Then embedded in paraffin,Dyed with HE,saffron O,tartrate-resistant acid phosphatase.COLII、COLX and osteocalcin were detected by immunohistochemistry.All tissue slice images were compared with CT images.ResultsThis technology clearly revealed callus morphology during fracture healing.At day 5 after fracture,calluses were mainly in the form of osseous calluses.These are formed by intramembranous ossification,shown as thick-walled grids or radii.A few cartilaginous calluses formed by endochondral ossification were found on day 5;these had relatively low density.On days 10 and 15,callus formation by endochondral ossification reached its peak,with differences in morphology and density involving the transformation of the cartilaginous callus.There were also a small number of fibrous calluses.On day 21,the cartilaginous calluses had disappeared and mainly osseous calluses remained.On day 28,the fracture remodeled and part of the callus was absorbed.In cartilage callus,mainly on the 10 th day of fracture,saffron-O dyed early chondrocytes dark red or orange.Osteoclasts were stained red with tartrate-resistant acid phosphatase and were found in different regions at different stages.On the 15 th and 21 st day of fracture,tartrate-resistant acid phosphatase staining stained red osteoclasts at each stage,and Col II、Col X and osteocalcin were detected by immunohistochemistry.ConclusionThe technique could detect fracture healing,especially cartilage callus,osseous callus and remodeling,and the different expressions of II collagen(Col II),X collagen(Col X)and Osteocalcin were matched with the multi-stage synchronous radiation CT fracture healing process.