Accurate reduction of the hip is important for children with dislocated hips that undergo reduction. Plain radiographs are routinely used to evaluate the reduction but can be tricky to interpret. CT imaging is sometimes used but there are concerns of radiation exposure particularly in the children. Magnetic resonance imaging (MRI) is an effective method to evaluate the adequacy of the reduction, but limitations of MR imaging include longer scanning time, need for sedation and higher expense.
Gould et al recently conducted a study at the Alfred I. duPont Hospital for Children, Wilmington, DE, to provide an MRI protocol in DDH patients that does not require sedation and can be performed in <15 minutes.
They reviewed 34 consecutive MRI studies performed without sedation after spica cast placement in 24 developmental hip dysplasia patients. 97 % percent of studies were diagnostic, although 18% of examinations had significant motion artifact. T2-weighted fast spin echo sequences (a special type of MR sequence now routinely available) had the best overall scores and were performed in <3 minutes. T1 and fat-suppressed T2-weighted fast spin echo sequences (other sequences more commonly used today) did not score as well, and also required <3 minutes. Sequences like single-shot fast spin echo and three-dimensional (3D) gradient recovery sequence scored poorly.
Authors concluded that MRI is a useful tool in evaluating the hips without radiation exposure and without sedation in infants and toddlers after spica cast immobilization.
Orthopaedic surgeons can request these 2 sequences for accurate assessment of concentric reduction with a potential study time of 15 minutes, obviating the need for sedation.
This article outlines a possible method of using MR imaging to evaluate reduction after DDH closed/ or open reduction procedures. It is helpful to know the specific sequences that are better than others and also the fact that it is less time consuming than before and sedation is not required.