| Objective:To study the distence of bone fragment displaced influence on the fracture union of long diaphysis and the role of histomorphology changes among fracture union process through animal experiments,that can provide a theoretical basis for clinically doctors to use biology memory reasonablly to fix comminuted fracture of long bone.Methods: 120 New Zealand white rabbits , 4-month-old , not limited to male and female ,were randomly divided into 5 groups of 24. After the success of intravenous anesthesia, use tachnician drilling interception a wedge-shaped bone fragment at the central radial of the right forelimb of the rabbits.With two pieces of Kirschner wire fixed the bone fragment and the main bone, to maintain the fracture gap in different distance. Then divided into 5 groups according to the different distance,and the distance of 5 group were,group A(in situ fixed),group B(1/5 diameter of the radial shaft),group C(2/5 diameter),group D(3/5 diameter ),group E(4/5 diameter).Toke X-ray photos to make sure that the fixation was firmly and the division was exactly.The experimental animals were killed at 2,4,6,8weeks after operation in batch.Took X-ray photos to observe the fracture healing conditions,and scored by the standers of improved Gary X-ray. After generally observe the fracture place,then extration material, fractionated two halves lengthways, tissue sectioning.One half of the material make HE staining after tissue sectioned,observed the changes of fracture healing histomorphology by light microscope. Another half was carried on immuno histochemical testing,to ditermine BMP-2 expression values.Results: X-ray photos found, group A and group B was similar to X-ray findings.There was a large number of subperiosteal callus, fracture line fuzzy at 2 weeks. Callus began to shap and reconstruct at 4 weeks.At 6 weeks the fracture line had almost disappeared and the cavitas medullaris had recanalizationed but less regular.At 8 weeks fracture line had disappeared and cavitas medullaris restored. The X-ray findings of group C was similar to group D. Callus just began to reconstruct at 6 weeks and the cavitas medullaris restored but irregular at 8 weeks.The group E fracture line was clearly all long,the fragment had gradually been absorbed.Group A was the control group, scored every groups with the standers of improved Gary X-ray,use anallysis of bariance,the influence of fragment displaced distance on fracture healing has statistical significance (F=410.47,P<0.001). Time's effect to fracture healing also has Statistics Significance (F = 975.59, P <0.001).Observe the organization morphological: In group A and B there were woven bones in fracture gap, a large number of cartilage cells and osteoblasts can be seen, new trabecular bone has emerged at 2 weeks. Trabecular arranged regular, bony plates and early bone units emerged, osteoblasts increased and osteoclasts appeared occasionally in the gap.At 6 weeks fractures gap occured more bone building units and bone plates, osteoclasts increased. The new bone rebuild completely, there are more bone units, osteoblasts, osteoclasts, and bone trabecula become ruled at 8 weeks. Other groups compared with group A,the time of callus appeare and reconstruction was late, and relatively have smaller numbers of osteoblasts ,however,collagenoblasts increase, fracture healing delayed and nonunion,especilly in group C , D and E. Observed the value of BMP-2 expression by immunohistochemistry,the influence of fragment displaced distance on the value of BMP-2 has statistical significanc(eF=175.50,P<0.001). In group comparison, group B ( 0.968±0.013 ) compared with group A(0.979±0.012)there was no significant difference,but group C(0.953±0.019),group D(0.933±0.015),group E(0.745±0.014) compared with group A there was prominent difference(P<0.001).There was statistically significant only between group E(0.716±0.032) and goup A(0.878±0.039)(P <0.001).At 6 and 8 weeks every groups has significance difference(P>0.05).Conclusion: The distance of fracture fragment displaced can influence fracture healing, with the distance increased, bony callus was gradually reduced in fracture gap, the time of fracture line disappeared and callus begained to rebuild delayed,and the fracture fragment was gradually absorbed.The larger distance of the fragment displaced,the more obviously influence on fracture healing.When the distance of fracture fragment displaced less than 2/5diameter of the bone shaft,would have no influence on fracture healing, when the distance of fracture fragment displaced was 2/5 to 3/5,the fracture healing delayed, when the distance of fracture fragment displaced was 4/5 ,the fracture nonunion .In order to reduce the incidence of the healing delayed and nonunion, with regard to the distance more than 2/5 diameter of the bone shaft should be resetted. |
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