The accuracy of magnetic resonance arthrography in hip arthroscopic labral revision surgery.

The interpretation of a magnetic resonance arthrogram (MRA) after a labral tear has been surgically treated can be challenging and there is no published evidence on its accuracy. The aim of this study was to evaluate the MRA accuracy in identifying labral pathology after hip arthroscopy. We reviewed 60 patients who had undergone a revision hip arthroscopy. Patients were divided into two groups. First, a study group (n = 40), which included patients who had undergone arthroscopic labral surgery at index operation. Secondly, there was a control group (n = 20), for patients who had not undergone labral surgery at index procedure. Findings regarding labral pathologies at MRA and at revision surgery were recorded. Sensitivity for MRA after hip arthroscopy was 53% and 71% in the study and control groups, respectively; specificity was 50% and 92%, positive predictive value was 81% and 83%, negative predictive value was 21% and 86% and accuracy was 53% and 85%. We conclude that the MRA is not reliable after hip arthroscopy where a labral tear has been addressed. When a labral tear has been repaired or partial labral excision has been performed, a postoperative MRA may inaccurately diagnose the presence of a persistent, recurrent, or unhealed tear.