Sonographic versus magnetic resonance arthrographic evaluation of full-thickness rotator cuff tears in millimeters.

Preoperative knowledge of full-thickness rotator cuff tear size is important in counseling patients because tear size affects the choice of surgical techniques and the functional outcome of surgery. Twenty-six shoulders of twenty-five consecutive patients were included in a prospective study that compared the preoperative accuracy of magnetic resonance arthrography and ultrasonography for tear size in millimeters with intraoperative findings. No significant differences were found between intraoperative, ultrasonographic, and magnetic resonance arthrographic data for the width of tears. Adoption of a "curved line measurement" for ultrasonographic evaluation of large tears eliminated the tendency of ultrasonography to underestimate tears greater than or equal to 35 mm in width. No significant differences were found between intraoperative, ultrasonographic, and magnetic resonancearthrographic data for retraction of tears. However, a limitation of ultrasonography to evaluate retractions of more than 30 mm was found. Therefore, ultrasound is of equal value for tears less than 30 mm, but magnetic resonance arthrography is more accurate for tears greater than 30 mm.