MRI in Hip Dysplasia: How to Shorten your MR-Protocol?

Abstract

Objective: Congenital hip dysplasia is a common orthopedic disorder in childhood. MRI is widely used to image high grade dysplastic hips after reduction and fixation within a cast. The purpose of this study was to optimize and shorten the MR study to the requests of the pediatric orthopedic surgeons. Material and Methods: 13 consecutive MR studies of the hip were included in the study (1-5 months of age) between 2003 and 2011. Two pediatric orthopedic surgeons, who were blind for the diagnosis and therapy of the study patients, evaluated all magnetic resonance images (MRI) to determine the type of hip dysplasia. The usefulness of the MR-images was assessed using a 5-point scale. The type of hip dysplasia was assessed using the Tonnis criteria. In addition two radiologists in consensus evaluated the status of sedation and motion artifacts. Original MRI-reports were reviewed. Results: The most valuable sequences for the position of the femoral head and the evaluation of the anatomic details of the 13 MR-studies were: (a) In coronal planes: TIRM 3 mm (Score 4.6), T2 TSE 3mm (Score 4.1). (b) In axial planes: PD axial 3mm (Score 4.75), DESS reformats 1.5 mm (Score 4.5). (c) All sagittal sequences and non-fat saturated T1w images were not supportive for the orthopedic surgeons. Mild and major motion artifacts are observed in 33% of the patients with sedation and in 71% without sedation. Conclusion: After reduction of high-grade hip dysplasia and Spica-cast fixation, MRI examination offers valuable information for the orthopedic surgeon. The MRI study may fulfill the orthopedic surgeon’s needs using only one coronal and axial plane (e.g. T2w, PD or DESS) to image the dysplastic hip after treatment in a Spica-cast reliably. The shortening of the protocol may reduce the requirement of general anesthesia or sedation, however optimal images without motion artifacts play an important role in image interpretation.