Objectives: Although the teres minor has received little attention in the literature compared to the other musculotendinous units of the rotator cuff, it is an important component of shoulder function. Our purpose was to study the appearance of the teres minor muscle on CT and MRI images in various patterns of rotator cuff tears.
Materials and methods: We analyzed the appearance of the teres minor according to the Walch classification (normal, hypertrophic, atrophic, or absent) in 1,332 CT and in 240 MRI images of rotator cuff tears and we correlated it with the type of rotator cuff tears, time period between initial onset of symptoms and diagnostic imaging, age of the patient at the time of imaging, and degree of fatty infiltration of other rotator cuff muscles.
Results: The teres minor was classified as normal in 90.8% of cases, hypertrophic in 5.8%, atrophic in 3.2%, and absent in 0.2%. Significant variability existed in the appearance of the teres minor muscle among different patterns of rotator cuff tears in the CT (P < 0.0001) and MRI groups (P < 0.0001). The teres minor appeared most frequently hypertrophic in anterior tears and atrophic in posterior-superior tears.
Conclusions: The teres minor was normal in most rotator cuff tears. A morphologic classification system allowed the appearance of the teres minor to be defined in isolated and multiple rotator cuff tears in CT and MRI images.