MRI/MR Arthrogram

MRI is the reference imaging technique for evaluating labral tears, cartilage lesions, and other intra-articular soft-tissue pathology of the hip1. There are two distinct approaches to imaging the hip prior to arthroscopy.

Non-contrast MRI is a high-resolution, small field-of-view (15–20 cm) study performed with flexible surface coils, obtained in axial, coronal, and sagittal planes using proton-density fat-saturated sequences, which outperform standard T1/T2 sequences for differentiating cartilage from the labrum and joint capsule. Many high-volume hip preservation centers now use 3T non-contrast MRI as their default study, since it avoids the morbidity and added cost of intra-articular contrast injection while still adequately characterizing labral tears and identifying alternative extra-articular pathology such as gluteal tendinopathy, ischiofemoral impingement, stress fracture, or neoplasm2.

MR arthrography (MRA) involves injecting dilute gadolinium contrast (approximately 0.0025 mmol/mL) directly into the joint to distend the capsule. Distension improves delineation of the labral-chondral junction and allows the radiologist to differentiate a true labral tear from normal intrasubstance signal variation3. Systematic review evidence supports direct MRA over unenhanced MRI and indirect MRA specifically for detecting labral and cartilage abnormalities, and direct MRA remains the traditional gold standard for labral tear detection. MRA sensitivity for labral tears is strong, 87% specificity around 64% depending on protocol and imaging plane4.

In practice, most centers reserve MRA for equivocal presentations, revision cases, or detailed pre-operative mapping when a labral repair or capsular procedure is anticipated, while using non-contrast 3T MRI as an adequate first-line study in more straightforward cases1.