Comparison of hip reduction using magnetic resonance imaging or computed tomography in hip dysplasia

The purpose of this paper was to compare the use of computed tomography (CT) versus magnetic resonance imaging (MRI) to evaluate hip reduction in patients with dysplasia of the hip.

A retrospective review of postoperative pelvic CT and MRI in patients <13 months of age with hip dysplasia was performed. Scanner time, anesthesia requirement, cost, and radiation dosage were recorded. Hips were classified as dislocated, subluxated, or reduced. Sensitivity and specificity of CT and MRI were calculated. The outcomes of the subluxated hips were followed.

Thirty-two CT scans and 33 MRI scans in 39 patients were evaluated. CT scanner time was 2.8 minutes, which was significantly less than the 8.9 minutes required for MRI (P=0.0001). Postoperative anesthesia was only required for 1 CT case. Average cost of CT examination was $788 and $1104 for MRI. Average radiation dose with CT examinations was 1 mSv. Of the postoperative nonsubluxated hips (n=30 for CT and n=37 for MRI), CT demonstrated a sensitivity of 100% and a specificity of 96%, whereas MRI exhibited a sensitivity of 100% and a specificity of 100%. Of the postoperative subluxated hips, 66.7% spontaneously reduced, 22.2% remained subluxated, and 11.1% redislocated.

This is the first study to compare these imaging modalities in the evaluation of hip reduction in DDH. This study affirms MRI as an alternative to CT scan. The sensitivity and specificity of both modalities appears excellent. Similar to other studies, a large percentage of subluxated hips in both groups reduce without additional surgical intervention.

Diagnostic level II.