Clinically occult avascular necrosis of the hip: prevalence in an asymptomatic population at risk.

An abbreviated screening magnetic resonance (MR) imaging examination was used to determine the prevalence of clinically occult avascular necrosis (AVN) of the hip in 100 asymptomatic renal transplantation patients treated with corticosteroids. All patients were more than 18 years old, had been treated with corticosteroids for at least 6 months, and had no symptoms of AVN before MR imaging. Of the 100 patients screened, six were found to have clinically occult AVN at MR imaging (rate: 6%, with a 95% confidence interval of 2.2%-12.6%). No significant differences were found regarding the total dose of corticosteroids and exposure time between patients with and patients without asymptomatic AVN. The authors conclude that there is a significant prevalence of asymptomatic, clinically occult AVN among renal transplantation patients treated with corticosteroids and that a potentially low-cost screening MR imaging examination can be used to detect such disease.