Magnetic resonance imaging as the primary imaging modality in children presenting with acute non-traumatic hip pain

The role of magnetic resonance imaging (MRI) in children presenting with ac ute non-traumatic hip pain was evaluated prospectively. Hip MRI was perform ed in addition to standard investigations (arthrosonography +/- hip radiogr aphs) in 50 children presenting to the accident and emergency department of a paediatric hospital. MRI was performed on an open 0.23T system and compr ised gradient echo T1 weighted coronal, fast spin echo T2 weighted coronal and inversion recovery spin echo (IRSE) axial sequences. Diagnostic quality MRI examinations were obtained in 94% of children. The IRSE sequence was t he most reliable at determining underlying disorder (p<0.002). Interobserve r agreement on the MRI examinations was very good with unweighted <kappa> v alue of 0.89, 95% confidence intervals 0.79, 0.99. Sensitivity of MRI was 0 .79 (0.68, 0.90, specificity 1.00 (0.89, 1.00), accuracy 0.81 (0.70, 0.92), PPV 1.00 (0.89, 1), NPV 0.36 (0.25, 0.47). Sensitivity of standard imaging was 0.70 (0.54-0.86), specificity 0.57 (0.41, 0.73), accuracy 0.72 (0.56, 0.88), PPV 0.91 (0.75, 1.00), NPV 0.24 (0.08, 0.40). MRI correctly identifi ed all seven children with serious underlying disorder whereas conventional imaging correctly diagnosed only two. Pelvic musculoskeletal infection was associated with the combination of marked alteration in signal in tissues adjacent to a symptomatic hip and an erythrocyte sedimentation rate of >20 mm 1st h (p<0.0001). In conclusion, MRI is a practical, wed accepted and ac curate noninvasive imaging technique in children presenting with acute non- traumatic hip pain. Combined with inflammatory markers MRI can be used to d etermine those children who require aggressive management. Where it is avai lable, MRI is the imaging modality of choice in this condition.