[Reproducibility of radiological classification criteria of femur head necrosis].

AIM: To assess the reliability of commonly used radiographic features in osteonecrosis of the femoral head.

METHOD: For staging of avascular necrosis of the femoral head two different classification systems, Ficat and ARCO, were applied. To measure the size of the necrotic lesions the combined necrotic angle of Kerboul was used. Radiographs of 49 patients with osteonecrosis of the femoral head were graded by two observers at two different time points. The Spearman's correlation coefficient was calculated for intra- and inter-observer reliability.

RESULTS: We found good intra- (Spearman's correlation coefficient 0.81-0.87) and inter-observer reliability (0.71-0.74) for the Kerboul's angle. Reliability for the ARCO stage classification was acceptable for intra-observer but unacceptable for inter-observer agreement. The reproducibility of the Ficat staging system was unacceptable.

CONCLUSION: The Kerboul angle is a reliable measurement to assess the severity of the osteonecrotic defects in femoral heads. The staging systems of Ficat and ARCO are not sufficiently reliable to assess the disease status of the hip alone.