To examine the relative frequency of patients with idiopathic osteonecrosis of the femoral head (ION) and its trend in recent years, all inclusive patients with ION who underwent surgery during the past 16.5 years at our hospital were studied. The total 16.5-year period was divided into 3, and change of the number of patients with ION per 10,000 initial visit patients at our department during the 3 periods was analyzed. The analysis was performed by classifying patients by gender and inducible

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... actors (steroid and alcohol). The total number of patients with ION did not show any significant changes during the period. The number of patients with ION with steroid use, especially female patients, had increased significantly, whereas female patients without any inducible factors significantly deceased. Our results should be tested in a larger sample study.