Evaluation of the risk factors of avascular necrosis of the femoral head in developmental dysplasia of the hip in infants younger than 18 months of age.

Sixty-seven dysplastic hips of 54 infants with an average age of 11.9 months were treated by the same surgical technique, including iliopsoas and adductor tenotomies via medial approach and arthrography for verification of the concentric reduction. The average follow-up period was 44.5 months. The rate of overall avascular necrosis (AVN) was 27% and that of severe AVN was 7%. With the numbers available in the study, a statistically significant relationship could not be found between the rate and severity of AVN and several preoperative and intraoperative components such as age, sex, side, dislocation grade, development of the ossific nucleus and qualitv of intraoperative reduction. Nevertheless, hips of infants treated between 13 months and 15 months of age, hips of male patients and left hips had slightly higher ratios of ischemic changes that were not statistically significant.