Use of Pre-operative Magnetic Resonance Arthrography in Femoroacetabular Impingement

Background: Magnetic resonance arthrography is the current method of choice for investigating patients with a clinical diagnosis of femoroacetabular impingement prior to performing hip arthroscopy. The aim of our study was to assess the efficacy of this investigation by comparing the findings of MR arthrogram with those found at arthroscopy, with reference to labral tears and chondral damage. Methods: A prospective trial to investigate the sensitivity, specificity, accuracy and predictive value of MRA for diagnosis of labral tears and chondral defects. Over a 25-month period 69 hips undergoing hip arthroscopy were investigated with MRA prior to the definitive operative procedure. MRA findings were compared to the intraoperative findings. Results: In the assessment of labral tears, MRA demonstrated a sensitivity of 81% with a specificity of 51% and an accuracy of 58%. Positive predictive value of MRA was 33% and negative predictive value 90%. For chondral defects MRA demonstrated a sensitivity of 17%, a specificity of 100% and accuracy of 55%. Positive predictive value of MRA was 100% and negative predictive value was 51%. Conclusions: In what the authors believe to be the first study to explore both chondral injury and labral tears in a prospective manner and looking specifically at accuracy, it can be seen that the MRA has poor accuracy for both pathologies. We recommend a moved away from MRA, which is an invasive procedure with associated risks. We recommend the use of computed tomography with three dimensional reconstruction to clearly identify the osseous pathology.