BACKGROUND: Spiral CT three-dimensional reconstruction has been used to observe the femoral head coverage fate of developmental dislocation of the hip (DDH). However, most of research containing certain observing point, which lack of long-term follow-up and comprehensive analysis. This article wants to fill the gaps.OBJECTIVE: To study changes of femoral head coverage fate in DDH child after 3 years treatment by CT reconstruction. METHODS: Totally 73 patients with unilateral DDH treated by aluminium plate after manual close reduction was selected. Spiral CT scanning of femoral articulation was performed at 1 day before and 12, 24, and 36 months after reduction to measure the femoral head coverage fate changes. The normal hip of patient was served as control.RESULTS AND CONCLUSION: All patients were included in the 42-53 months follow-up. After treatment, the femoral head coverage fate of patients were obviously than that of before treatment (P<0.01), which gradually approach to the normal level in 3 years, the first year after treatment is a key period for acetabulum development.