Teres Minor Hypertrophy Is Responsible For Maintaining Forward Elevation And Function In Patients With Massive Rotator Cuff Tears
Anuli N. Mkparu, MD, Lauren M. Fabian, MD, Thomas R. Gardner, BSE, Christopher S. Ahmad, MD, Louis U. Bigliani, MS, William N. Levine, MD
PURPOSE OF STUDY
While many patients with massive rotator cuff tears present with loss of active shoulder motion, other patients with such tears have remarkable maintenance of mobility. One theory that accounts for this is the idea of axial plane balance of the anterior (subscapularis) and posterior (teres minor) cuff. In the setting of a massive tear, preservation of such a balance requires hypertrophy of the teres minor. We hypothesize that hypertrophy of the teres minor in patients with massive rotator cuff tears is responsible for maintaining forward elevation and better subjective assessment of function.
A retrospective review of charts for 60 patients was performed. The cohort was divided into three, patients with 1) No rotator cuff tear, No-Tear; 2) Massive rotator cuff tear and good forward elevation, Tear-FE and 3) Massive rotator cuff tear with poor forward elevation, Tear-Poor FE. 3D MRI analysis was done and the cross-sectional area of each of the 4 rotator cuff muscles was measured. The ratio of the teres minor cross section was compared to the subscapularis and the total rotator cuff cross-section. A simple shoulder test was also obtained on each patient, as a measure of the patients’ subjective assessment of their function. Statistical analysis was done using one-way ANOVA and Dunnett's multiple comparison test.
SUMMARY OF RESULTS
The Teres Minor/Total Rotator Cuff ratio was similar in No-Tear (0.14 ±0.03) and Tear-Poor FE (0.14 ± 0.04) and larger (p<0.0001) in Tear-FE (0.20 ± 0.05). The Teres Minor/ Subscapularis ratio was similar in No-Tear (0.33 ± 0.12) and Tear-Poor FE (0.30 ± 0.13) and larger (p=0.0012) in Tear-FE (0.44 ± 0.13). The difference in FE between both arms was similar for Tear-FE (0.00 ± 0.00°) and No Tear (1.0 ± 4.4°) and larger (p<0.0001) for Tear poor-FE (63.5 ± 43.4°). The Simple Shoulder Test scores were similar for No-Tear (8.7 ± 3.0) and Tear-FE (6.8 ± 3.7) but significantly smaller (p=0.0173) for Tear Poor-FE (2.6 ± 2.2).
Hypertrophy of the teres minor is responsible for maintaining forward elevation and overall function in patients with massive rotator cuff tears.