BACKGROUNDMany potential causative factors are related to the initiation and progression of osteonecrosis of the femoral head. The aim of this research was to investigate the etiology and clinical features of osteonecrosis of the femoral head in Chinese patients.

METHODSFrom January 1990 to July 2011, 643 cases of osteonecrosis of the femoral head were investigated retrospectively to analyze the potential causative factors, age, gender, latency period, time from the onset of pain to diagnosis, and Association Research Circulation Osseous stage.

RESULTSOf 643 cases, 315 cases were bilateral and 328 cases were unilateral, with an average age of (47.55 ± 15.27) years. In the steroid-induced group, the average age at symptom onset was (41.80 ± 15.47) years, and the median duration from taking steroid to the onset of pain was 36 months. The underlying diseases in the steroid-induced osteonecrosis of the femoral head group consisted of autoimmune and other diseases, of which systemic lupus erythematosus was the most common. In the alcohol-induced group, the average age at onset of symptoms was (48.06 ± 11.90) years and the median time of habitual alcohol use was 240 months. In the traumatic group, the average age was (51.43 ± 14.23) years and the median time from trauma to the onset of pain was 20 months. In the idiopathic group, the average age was (50.33 ± 15.88) years. Of the total of 958 hips, 647 were at stage III or IV. The stage at diagnosis was earlier in the steroid-induced group than in the alcohol-induced, traumatic, or idiopathic groups.

CONCLUSIONSSteroid use is the most common cause for osteonecrosis of the femoral head in this study. The age at diagnosis, time from the onset of pain to diagnosis, and stage were significantly earlier in the steroid-induced group.