| Objective:To detect the articular cartilage changes of the hip joint at early stage of the osteonecrosis of femoral head(ONFH),and provide theoretic evidence for understanding the pathomechanism of ONFH and performing rational therapy.Methods:This study was divided into three parts,(1) The animal model of subchondral bone detect of femoral head was established,articular cartilage changes of femoral head were evaluated by histological and histochemical assay at various time point.18 adult hybrid dogs were applied for bone defect model of femoral head.Of the femoral heads, the left was applied for bone defect model,the right for shame-operation.5,5,and 8 animals were sacreficed respectively at 4,12 and 24 weeks after operation and the femoral heads were received for examinations.The X-rays films were taken just before the animals were sacreficed.After the cartilage specimens were decalcified,dehydrated and embedded,6 u thick sections were made.They were stained with hematoxylin-eosin, sirius-red and toilude blue.The biochemical assay were performed.(2) the articular cartilage changes of stageⅡ,Ⅲof ONFH were determined by delayed gadolinium-enhanced magnetic resonance imaging of cartilage(dGEMRIC).5 asymptomatic volunteers and 20 patients with ONFH participated in the test.According to ARCO classification of ONFH,stageⅡin 11 cases,stageⅢin 9 cases,they were all steroid type.All participants underwent the tests by dGEMRIC(1.5 T),and the data of T1Gd were collected and analyzed by means of Matlab and mrimapper software.(3) The biological markers of cartilage were analyzed to determine the cartilage metabolic changes of ONFH.Serum levels of Cartilage oligomeric matrix protein(COMP) and Keratan sulfate(KS) were quantified with a sandwich-ELISA for ten cases of ONFH and five asymptomatic volunteers respectively. Results:(1) At 12 and 24 weeks after operation for bone defect,cartilage histology and biochemistry demonstrated the signs of articular cartilage pathological changes.The arrangement of chondrocytes was in disorder.The number of chondrocytes decreased. The cartilage surface lost its smoothness,and these changes were more severe seen in the area next to the bone defect.Fibrosis and vasiformation were found.Tidemark had the changes of discontinuation and veil.Glycosaminoglycans decreased.(2) The values of T1Gd obtained from the patients with stageⅡ,ⅢONFH,and the healthy volunteers were 441.13±41.32,363.11±56.39,and 544.2±27.83 respectively.The values of T1 Gd in the patients of stageⅡ,ⅢONFH were lower than in volunteers,there was a significant difference in T1Gd between the patients of stageⅡorⅢand the healthy volunteers (P＜0.001).The values of T1Gd of the patients of stageⅢwas 17.7%lower than the patients of stageⅡ,and the difference between two stages was significant statistically (P＜0.05).(3) The serum level of KS was 123.28ng/ml±17.93,105.3ng/ml±14.97 in patients and volunteers respectively;and serum level of COMP was 588.44 ng/ml±99.68, 542.5 ng/ml±28.29 in patients and volunteers respectively.Compared with the volunteer group,there was an increase tendency in the serum level of both KS and COMP,but without statistic significant difference.Conclusion:At early satge of ONFH,articular cartilage of the femoral head appears abnormal metabolic changes,represented by the loss of GAG in the articular cartilage, and aggravated as worsening of ONFH.This demonstrates the metabolism and function of the articular cartilage can be influenced at early stages of ONFH,but the mechanism is not clear and further study is needed.
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