Location of Rotator Cuff Tear Initiation A Magnetic Resonance Imaging Study of 191 Shoulders

Background: Degenerative rotator cuff tears (RCTs) are generally thought to originate at the anterior margin of the supraspinatus tendon. However, a recent ultrasonography study suggested that they might originate more posteriorly than originally thought, perhaps even from the isolated infraspinatus (ISP) tendon, and propagate toward the anterior supraspinatus. Hypothesis/Purpose: It was hypothesized that this finding could be reproduced with magnetic resonance imaging (MRI). The purpose was to determine the most common location of degenerative RCTs by using 3-dimensional multiplanar MRI reconstruction. It was assumed that the location of the partial-thickness tears would identify the area of the initiation of full-thickness tears. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A retrospective analysis was conducted including 245 patients who had RCTs (nearly full-or partial-thickness tears) at the outpatient department between January 2011 and December 2013. RCTs were measured on 3-dimensional multiplanar reconstruction MRI with OsiriX software. The width and distance from the biceps tendon to the anterior margin of the tear were measured on T2-weighted sagittal images. In a spreadsheet, columns of consecutive numbers represented the size of each tear (anteroposterior width) and their locations with respect to the biceps brachii tendon. Data were pooled to graphically represent the width and location of all tears. Frequency histograms of the columns were made to visualize the distribution of tears. The tears were divided into 2 groups based on width (group A, <10 mm; group B, <20 and >= 10 mm) and analyzed for any differences in location related to size. Results: The mean width of all RCTs was 11.9 +/- 4.1 mm, and the mean length was 11.1 +/- 5.0 mm. Histograms showed the most common location of origin to be 9 to 10 mm posterior to the biceps tendon. The histograms of groups A and B showed similar tear location distributions, indicating that the region approximately 10 mm posterior to the biceps tendon is the most common site of tear initiation. Conclusion: These results demonstrate that degenerative RCTs most commonly originate from approximately 9 to 10 mm posterior to the biceps tendon.