Reliability and intraoperative validity of preoperative assessment of standardized plain radiographs in predicting bone loss at revision hip surgery

Background: The most challenging aspect of revision hip surgery is the mana gement of bone loss. A reliable and valid measure of bone loss is important since it will aid in future studies of hip revisions and in preoperative p lanning. We developed a measure of femoral and acetabular bone loss associa ted with failed total hip arthroplasty. The purpose of the present study wa s to measure the reliability and the intraoperative validity of this measur e and to determine how it may be useful in preoperative planning. Methods: From July 1997 to December 1998, forty-five consecutive patients w ith a failed hip prosthesis in need of revision surgery were prospectively followed. Three general orthopaedic surgeons were taught the radiographic c lassification system, and two of them classified standardized preoperative anteroposterior and lateral hip radiographs with use of the system. Interob server testing was carried out in a blinded fashion. These results were the n compared with the intraoperative findings of the third surgeon, who was b linded to the preoperative ratings. Kappa statistics (unweighted and weight ed) were used to assess correlation. Interobserver reliability was assessed by examining the agreement between the two preoperative raters. Prognostic validity was assessed by examining the agreement between the assessment by either Rater 1 or Rater 2 and the intraoperative assessment (reference sta ndard). Results: With regard to the assessments of both the femur and the acetabulu m, there was significant agreement (p < 0.0001) between the preoperative ra ters (reliability), with weighted kappa values of >0.75. There was also sig nificant agreement (p < 0.0001) between each rater's assessment and the int raoperative assessment (validity) of both the femur and the acetabulum, wit h weighted kappa values of >0.75. Conclusions: With use of the newly developed classification system, preoper ative radiographs are reliable and valid for assessment of the severity of bone loss that will be found intraoperatively.