Tendon stump type on magnetic resonance imaging is a predictive factor for retear after arthroscopic rotator cuff repair

Background Fatty infiltration of the rotator cuff musculature increases in larger tears and is a factor in retearing. However, tearing may recur even in patients with small original tears and little fatty infiltration of the rotator cuff musculature. We devised a system to classify the rotator cuff tendon stump by magnetic resonance imaging (MRI) signal intensity and investigated prognosis-related factors associated with retear based on other MRI findings. Methods We analyzed and compared the signal intensity of the rotator cuff tendon stump and deltoid on preoperative T2-weighted fat-suppressed MRI in 305 patients who underwent primary arthroscopic rotator cuff repair. We also investigated the tear size, Goutallier stage, and global fatty degeneration index. Results In a type 1 stump, the tendon stump had a lower (darker) signal intensity than the deltoid. In type 2, the signal intensities of the tendon stump and deltoid were equivalent. In type 3, the signal intensity of the tendon stump was higher (whiter) than that of the deltoid. Multiple regression analysis of the association between retear and other parameters identified stump type (odds ratio [OR], 4.28), global fatty degeneration index (OR, 2.99), and anteroposterior tear size (OR, 1.06) as significant factors. The retear rates were 3.4% for type 1 stumps, 4.9% for type 2, and 17.7% for type 3. Conclusions Type 3 stumps had a significantly higher retear rate, suggesting that stump signal intensity may be an important indicator for assessing the stump's condition. Our stump classification may be useful in choosing suture techniques and postoperative therapies.