Imaging of traumatic dislocation of the hip in childhood

Background Traumatic hip dislocation in childhood is a rare consequence of violent trauma. After reduction, outcome is usually favourable although epiphyseal necrosis can occur. Reduction must be carried out as soon as possible and is achieved easily, although if the labrum is involved, surgery may be required to achieve complete reduction.Objective To analyze a retrospective series of traumatic hip dislocations in children, describing the therapeutic and imaging strategy.Materials and methods A total of 42 patients were studied. Their mean age was 10 years 3 months. All relevant radiographic, CT, MRI and radionuclide bone scan examinations were reviewed. Special attention was paid to associated lesions.Results In 22 patients the dislocation was caused by low-energy trauma. Road traffic accidents accounted for 17 dislocations. An acetabular fracture was present in six patients and the femoral head was fractured in three. Reduction was easily achieved in 31 patients. In 11 patients the postreduction radiograph and CT showed joint space asymmetry secondary to labral entrapment. Only two patients developed epiphyseal necrosis.Conclusions It has been difficult to define and evaluate accurate principles for a medical imaging strategy in this group of patients. Analysis of plain radiographs is essential before and after reduction of the joint, and it is important to perform postreduction CT in every patient whose joint space remains widened. A radionuclide bone scan should be performed between the second and third weeks after injury to assess epiphyseal vascularity. With the use of specific sequences, MRI may be an alternative modality to assess epiphyseal vitality.