OSTEONECROSIS OF THE HIP IN SLE - OBSERVER AND PATIENT VARIATION ON 6 METHODS OF ASSESSING FEMORAL-HEAD INVOLVEMENT

Osteonecrosis (ON) of the hip is a major cause of morbidity in patients with SLE. The lack of a quantitative method of measuring the amount of bone and articular surface involvement in ON has hindered the reporting of the progression of ON. We have developed quantitative methods to measure sphericity of the femoral head, the size and location of the collapsed segment and the size and location of the sclerotic bone along with the staging of ON of the hip. These measures were then read by five examiners (three rheumatologists and two orthopedic surgeons), who blindly reviewed AP views of the pelvis in five patients with varying stages of involvement, Measurements of stage, sphericity, lateral collapse and lateral sclerosis could be distinguished among patients (analysis of variance, max p = 0.0006), while medial collapse border and sclerosis could not (p = 0.056-0.257). There was interobserver agreement on stage, lateral and medial border, and size of the collapsed segment and lateral sclerosis size. Despite disagreement among examiners on sphericity, medial sclerosis border and size, the intraclass correlation coefficients ail exceeded 0.6 indicating reasonable agreement. This method is potentially useful for assessing the natural history and prognosis of osteonecrosis of the hip.