Inter- and intraobserver variation in staging patients with proven avascular necrosis of the hip

Diagnosis and treatment of avascular necrosis of the hip has long been predicated on the evaluation of plain radiographs, though other modalities (such as magnetic resonance imaging) are being increasingly used to aid in this evaluation. The Ficat classification is commonly used to assess plain radiographs and to help determine what treatment is appropriate for a given patient. It also is used to help evaluate patient outcome after surgical or nonsurgical treatment. This study was designed to evaluate the adequacy of plain radiographs in the evaluation of avascular necrosis of the hip. The plain radiographs of 25 hips with avascular necrosis were analyzed on 3 occasions by 6 readers (450 total readings). A clinically significant difference in radiographic staging was defined as a Stage I or II reading of the radiographs of a given hip on 1 reading and a separate reading of the same radiographs as Stage III or IV. By this definition, interobserver variability for the first reading resulted in clinically significant differences in 10 (40%) of the 25 hips. Intraobserver variability resulted in clinically significant differences for 10 (40%) of the 25 hips as well. The most experienced readers in the study (a total joint specialist and a musculoskeletal radiologist) were consistent internally in their readings in 90% of cases, and had a clinically significant difference in only 1 case (1%); however, these same 2 readers disagreed with one another on the staging of 9 (36%) of 25 hips, with 4 (16%) of 25 hips having a clinically significant difference in readings.(ABSTRACT TRUNCATED AT 250 WORDS)