Animal Model Standardization for Studying Avascular Necrosis of the Femoral Head in Legg-Calvé-Perthes Disease.

 Testing an experimental model for ischemic necrosis of the femoral head in Legg-Calvé-Perthes disease by evaluating gait, imaging and morphohistology.  The operation was done in 11 piglets. Necrosis by cerclage in the right femoral neck was induced. Piglets were divided into group A, with 8 animals, euthanizing two in the 2 , 4 , 6 , and 8 weeks, respectively; and group B, with 2 animals ( ), submitted to the surgical procedure without cerclage of the right femoral neck. The gait classification used was that of Etterlin. The frozen femurs were submitted to digital radiography and computed tomography. The height and width of the epiphysis and epiphysary coefficient were measured at study times. Light microscopy and immunohistochemistry with TGF-β1 were performed.  One animal died of sepsis in Group A. In this group, claudication was observed in all animals. On digital radiography and computed tomography, bone sclerosis, enlargement of the right femoral neck, flattening, collapse, and fragmentation of the right femoral head were observed. All epiphysis height and epiphysary coefficient values of the right femoral head were lower than the contralateral ones, in which were observed chondrocytes disordered and separated by gaps. A reduction in TGF-β1 expression was observed at 2 and 6 weeks in the right femoral head and at eight in the left. In group B, there were no signs of necrosis and gait was normal.  The model presented reproduced macroscopic necrosis on digital radiography, computed tomography, and microscopy. Gait evaluation showed a good correlation with other ischemia findings.  V. Diagnostic studies.