Osteonecrosis of the femoral head: using CT, MRI and gross specimen to characterize the location, shape and size of the lesion

Objective: To investigate the accuracy of using CT and MRI to characterize lesions of osteonecrosis of the femoral head (ONFH). Methods: Coronal CT and MRI scans were performed on 30 femoral head specimens collected from 23 patients who had undertaken hip arthroplasty owing to ONFH. The results were compared with findings from coronal sectional gross specimens. Two radiologists independently measured the volume of necrotic lesions from CT and MR images using computer software, and the results were averaged. The volume of specimens' necrotic lesion was measured using the water displacement method. Results: There was a high degree of consistency between CT, MRI and the coronal sectional gross specimen on the location, shape and spatial structure of lesions. Differences of the lesion volume measured from CT and MR images were not statistically significant between two radiologists. The necrotic lesion volumes measured from CT and MR images and gross specimens were 22.07 +/- 5.35, 22.21 +/- 5.15 and 21.12 +/- 4.96 cm(3), respectively, and the differences were not statistically significant (F = 0.396; p = 0.674). Conclusion: For patients with ONFH in Association Research Circulation Osseous stage III or above, CT and MRI can accurately display the characterization of lesion. Advances in knowledge: The size and location of necrotic lesions are major factors associated with femoral head collapse. CT is superior to MRI in identifying subchondral fracture. CT can help diagnose and predict the prognosis of ONFH.