Interstitial tears of the rotator cuff: difficulty in preoperative diagnosis.

BACKGROUND: Few studies have investigated the characteristic findings of preoperative magnetic resonance imaging (MRI) and the clinical and radiologic outcomes of interstitial tear of the rotator cuff treated with arthroscopic repair after tear completion.

METHODS: Forty-one patients (14 men and 27 women; mean age, 56.5 years) with arthroscopically confirmed interstitial tears underwent single-row repair after tear completion. The minimum follow-up period was 2 years.

RESULTS: Twenty-eight patients (68.3%) were properly evaluated with MRI before surgery. Seven cases (17.1%) were misdiagnosed as bursal-sided tears and 5 cases (12.2%) were misdiagnosed as articular-sided tears on the basis of presurgical MRI findings. Arthroscopy revealed fibrillation and dimpling of the tendon surface in all cases and congestion within the defect in 36 cases (87.8%). At the final follow-up, the visual analog scale score for pain during motion decreased to 0.8 from a preoperative mean of 6.1 (P <.001). Moreover, at the final follow-up, the mean University of California-Los Angeles score and Constant score improved from 15.7 and 51.8 to 32.1 and 83.8, respectively (P <.001 for all). At 9 months after surgery, MRI revealed no cases of retear.

CONCLUSION: Interstitial tears are difficult to diagnose before surgery because MRI findings may lead to the misdiagnosis of interstitial tears as articular- or bursal-sided tears. If MRI-based diagnosis is indicative of articular- or bursal-sided tears but arthroscopy reveals fibrillation and dimpling of the tendon surface, interstitial tears should be suspected. The defective sites in interstitial tears are usually accompanied by congestion.