Imaging and histopathological aspects in aseptic osteonecrosis of the femoral head.

Aseptic osteonecrosis causes various clinical manifestations, depending on its location, but has in common a histopathological and radiological substrate. Aseptic osteonecrosis of the femoral head is a condition whose pathogenesis remains unclear despite many theories developed so far, and the discovery of numerous risk factors. The objective of this study is to emphasize the role of imaging techniques and correlating histology and immunohistochemistry methods in order to more accurately stage the disease. This retrospective study was performed on a total of 103 patients with clinical and radiological suspicion of unilateral or bilateral osteonecrosis. For the diagnosis criteria, we used clinical information, pelvic X-ray images, magnetic resonance imaging (MRI) or computed tomography (CT). For the inclusion of patients in a disease stage, we used the Association Research Circulation Osseous (ARCO) classification system. For patients diagnosed at an advanced stage, who underwent hip arthroplasty, we harvested biological material necessary for the histopathological study. There were differences in the appearance and extent of the lesion on the histological samples compared to macroscopic examination and even those obtained through imaging means, particularly for patients in evolutionary stage III. Aspects such as the extension of the area of fibrosis, bone tissue remodeling, the density of the newly formed vascular network and degree of impairment of the cartilage, are determined more accurately using histology and immunohistochemistry techniques. Before classifying patients in a certain stage, after correlating clinical and imaging data, histopathological aspects have to be considered, particularly in patients in stages III and IV, in which total hip arthroplasty could be delayed.