18. THE TERES MINOR MUSCLE IN ROTATOR CUFF TEARS

Abstract

Purpose of the study: Data concerning the teres minor in the context of rotator cuff tears is scarce despite the fact that this muscle plays a crucial role in the event of an infraspinaus tear. The purpose of this study was to analyse the computed tomography and magnetic resonance images of the teres minor muscle in rotator cuff tears.

Material and method: The aspect of the teres minor muscle was studied in 1624 shoulders with rotator cuff tears. The axial and sagittal CT or MRI aspect was noted as normal, hypertrophic, atrophic or absent (Walch classification). We searched for correlations with the tendon torn, tear mechanism (trauma, degeneration, mixed), gender, dominance, time to imaging, age at imaging, and fatty infiltration of the supraspinatus, infraspinatus and subscapularis.

Results: The teres minor was noted normal in 90.9% of the shoulder, hypertrophic in 5.2%, atrophic in 3.2% and absent in 0.2%. The type of cuff tear had a significant impact (p< 0.0005). Regarding the aspect of the teres minor muscle, the highest percentages were as follows: normal for isolated supraspinatus tears, hypertrophic for supraspinatus and subscapularis tears, atrophic for posterosuperior (supraspinatus, infraspinatus ± teres minor) tears and absent for massive tears involving the supraspinatus, the infraspinatus ± the subscapularis (p< 0.0005). The correlation was statistically significant between the aspect of the teres minor and the grade of fatty infiltration of the infraspinatus (p< 0.0005) and the subscapularis (p< 0.0005).

Discussion: The aspect of an atrophic or absent teres minor, which correlates with the trumpet sign in massive tears, was only found in 3.5% of the tears. There would thus be few indications for latissimus dorsi transfer to restore active external rotation.