Avascular Necrosis of the Femoral Head : Correlation of Magnetic Resonance Imaging, Radiograph, Radionuclide Imaging, and Histological Findings

Byun, Young Soo; Lee, Kwang Suk; Park, Sang Won; Lee, Seok Woo

Abstract

Magnetic resonance imaging(MRI) appears to be the most sensitive modality for early diagnosis of avascular necrosis of the femoral head and has recently been recommanded as a means of strengthening individual treatment decisions, However, MR signal patterns in AVN has been described to vary widely. And the understanding of the anatomic and pathologic structures represented on the MRI thus appears desirable for improved tissue characterization, staging of disease, and therapeutic planning. The object of this study was to analyze the correlation of MRI, radiographic staging, radionuclide imaging, and histological findings in AVN of the femoral head. The authors analyzed retrospectively 30 patients(36 hips) of AVN of the femoral head who underwent bipolar hemiarthroplasty or total hip replacement arthroplasty at Korea University Hospital from Nov. 1990 to Oct. 1993. The radiographic stage was evaluated according to Ficat and Arlet classification, and MRI was evaluated according to Mitchell et al. classification. The histologic changes corresponding to MRI abnormalities were assessed in 10 fresh surgical specimens. The obtained results were as follows; 1. Nine cases (25%) were class A, 3 class B (8%), 6 class C (17%) and 18 class D(50%) by Michell et al. classification on MRI and typical double line sign was found in 20 cases(56%). 2. Most of the cases of Ficat and Arlet stage II in simple radiograph showed MR class A or B, and stage III and IV showed class C or D. 3. There cases(10%) showed false negative studies in radionuclide imaging. 4. The necrotic bone & marrow and amorphous cellular debris represented the low signal intensity on both T1WI and T2WI, and repairing tissue, thickened trabeculae with mesenchymal cell infiltration was low signal intensity in T1WI and intermediate signal intensity in T2WI, and fibrous tissue was low signal intensity on both T1WI and T2WI. 5. MR classification by Mitchell et al. was not correlated with histological finding in respect of progression. Above results suggest that MRI provide the information about accurate anatomical location and involved site of necrosis, while MR classification by Mitchell et al. was not useful for staging of pathogenic process of AVN of the femoral head. The therapeutic plan and modalities have to be estabilished by comprehensive analysis of MRI, simple radiograph and other diagnostic modalities.