Risk factors for failed closed reduction in dislocated developmental dysplastic hips

AIM OF THE STUDY: The present study aimed to identify risk factors for unsuccessful CR. INTRODUCTION: Closed reduction (CR) represents the gold standard for treatment of developmental dysplasia of the hip (DDH), but to a minor percentage, it fails to reduce dysplastic hips successfully. METHODS: Seventy-three dysplastic hips underwent closed reduction and post-interventional MRI of the pelvis. MRIs were evaluated for successful reduction of the hip, volumes of femoral heads, and acetabular diameter. Initial treatment results were correlated to AC angles at two years of follow-up. Contralateral, healthy hips served as control. RESULTS: Out of 73 instable, dysplastic hips, there were nine cases of CR failure. These cases showed significantly increased femoral head volumes (p = 0.002) and a significantly (p = 0.02) larger ratio of femoral head volume to acetabular opening area. There was no significant difference (p = 0.15) in acetabular diameter between both groups. At two years of follow-up, AC angles were significantly (p = 0.003) larger and pathologic in cases of CR failure. CONCLUSION: Exclusive enlargement of the femoral head is a risk factor for unsuccessful reduction and its ratio to the acetabular opening surface is predictive for CR success in DDH.