The Effect Of Subtrochanteric Varus Osteotomy To Vascularization And Endochondral Ossification Of The Femoral Head In Rabbit Model Of Perthes' Disease

ObjectivePerthes'disease is still an enigmatic disease after it was described 100 years,and the ideal treatment of it is difficult to get.Lookaround reviews of the literature,the treatment of Perthes'disease with subtrochanteric varus osteotomy has good results.The aim of this study was to explore the change and their significance of VEGF expression in the femoral head after subtrochanteric varus osteotomy in a rabbit model,and to appraise wheather subtrochanteric varus osteotomy can promote new vascular invasion and cartilaginous ossification in the femoral head epiphysial cartilage.Materials and methodsThirty-four 2～2.5-month-old New Zealand rabbits were used(weighing 1.8～2.0Kg). A rabbit model of Perthes'disease was made by excision of right ligamentum teres and retinacular blood supplies of femoral head. At 2 weeks,2 rabbits were selected randomly, histological observations of the femoral head proved that the model of Perthes'disease was made successfully.Thirty-two New Zealand rabbits were divided into groups A and B randomly.Group B were operated with subtrochanteric varus osteotomy at 2 weeks after Perthes'disease model. 4 rabbites in each experimental goup were selected randomly and killed at 2,4,6,8 weeks.The gross appearance,X-ray film, abdominal aortography and histological observations (HE,VEGF) were carried out at 2,4,6,8 weeks after operation;16 left femoral heads were selected randomly from group A and B,which was the blank group,the right femoral heads of group A was the control group and the right femoral heads of group B was the test group. All the data were analyzed by the software SPSS 17.0.ResultsThe rabbit model of Perthes'disease was made successfully;None of rabbits was dead. General observation:All the left femoral heads of group A and B were in grade 0 of the femoral head's general observation grade at all time points after operation.The result of general observation of the right femoral heads of group A at two weeks after operation(2 cases in grade 1,2 cases in grade 2),at four weeks(1 case in grade 1,1 case in grade 2,2 cases in grade 3),at six weeks(1 case in grade1,3 cases in grade 3),at eight weeks(2 cases in grade 2,2 cases in grade 2); The result of general observation of the right femoral heads of group B at two,four,six weeks after operation(2 cases in grade 1,2 cases in grade 2),at eight weeks(2 cases in grade 1,1case in grade 2,1 case in grade 3).The results of X-ray: All the left femoral heads of group A and B were in gradeⅠof the femoral head's X-ray grade,which were normal. The respective result of X-ray of the right femoral heads of group A and B at two weeks after operation(2 cases in gradeⅠ,2 cases in gradeⅡ); The result of X-ray of the right femoral heads of group A at four weeks after operation(4 cases in gradeⅡ),at six weeks(2 cases in gradeⅡ,2 cases in gradeⅢ),at eight weeks(1 case in gradeⅡ,2 cases in gradeⅢ,1 case in gradeⅣ); At four,six and eight weeks,all the right femoral heads of group B were in gradeⅡof the femoral head's X-ray grade.Abdominal aortography data: Visually,There was no difference in both right superficial and profunda femoral arteries by radiographic examinations,and their branches of group A as compared with the left. There were increased number in both right superficial and profunda femoral arteries by radiographic examinations,and their branches of group B as compared with the left.There were increased vascularity in the region of the operated proximal femur.The HE staining observation:By 2 weeks,many empty lacunae were observed in the right femoral head epiphyseal cartilage of the 2 rabbits which were killed by two weeks after the induction of ischemia.The bone marrow cavity filled by the amorphous debris;Trabecular bone fragmented into a sheet or compressed into blocks,but the repair phenomenon was not observed.So,the rabbit model of Perthes'disease was made successfully.The femoral heads had no necrosis changes in blank group.At 2,4,6,8weeks after subtrochanteric varus osteotomy,neovascularization was observed at the periphery of the infarcted femoral head.Vascular granulation tissue was consisted of capillaries,inflammatory cells and fibroblastic cells. Vascular granulation tissue were seen invading the necrotic marrow space,and the resorption of dead bone.However,there were obviously bone reparation and new bone formation at 4 weeks after subtrochanteric varus osteotomy in group B;There were no bone reparation and new bone formation until the 6th weeks in group A.Immunohistochemistry staining:In the epiphyseal cartilage of the femoral heads of blank group,an intensive VEGF immunoreactivity(VEGF-IR) was found in the hypertrophic zone , and a low level of VEGF-IR in the proliferative zone at all time points.There were statistically significant differences in the ratios of VEGF+ cells in hypertrophic zone of the femoral heads between test group and control group at all time points(P<0.001),but the ratios of VEGF+ cells in hypertrophic zone of the femoral heads of test group and control group were significantly lower than blank group at 2,4,6 weeks,there were not reached a considerable level until the 8 weeks after subtrochanteric varus osteotomy of the three groups. The ratios of VEGF+ cells in the proliferative zone of the femoral heads of blank group were significantly lower than test group and control group at all time points.There were statistically significant differences in the ratios of VEGF+ cells in proliferative zone of the femoral heads between test group,control group and blank group by pairwise comparison at all time points(P<0.001). The ratios of VEGF+ cells of test group were significantly higher than blank group at all time points,which was increased with time.Conclusions1,It is obvious that VEGF act a key regulator that couples angiogenesis,cartilage remodeling,and ossification after ischemic damage to restore endochondral ossification in the epiphyseal cartilage.2,Subtrochanteric varus osteotomy can promote vascular invasion in the region of the operated proximal femur.3,Subtrochanteric varus osteotomy can promote VEGF upregulation and the repair of ischemic necrosis of the femoral head,and can shorten the course of Perthes'disease.