Ultrasound was superior to MRI in diagnosing partial-thickness subscapularis tear, according to a study published in the journal Arthroscopy.¹

A total of 437 patients who underwent arthroscopic rotator cuff repair between January 2019 and December 2020 were recruited for this study to compare ultrasonography (US) and magnetic resonance imaging (MRI) in preoperative diagnoses of subscapularis tears using shoulder arthroscopy as the gold standard. The study did not include patients with past history of shoulder fracture or surgery, unstable shoulder joint and systemic inflammatory disease.

On arthroscopy, 157 patients were found to have subscapularis tears. Of these, 126 were partial-thickness tears. According to the results, ultrasound could correctly diagnose the subscapularis tears in 122 out of the 157 patients with an overall sensitivity of 77.7% vis-à-vis 49.7% sensitivity of MRI.

USG also reliably diagnosed partial thickness tears in 93 patients out of 126 positive patients and 276 of 311 negative with 84.4% accuracy, 73.8% sensitivity and 88.7% specificity. The sensitivity and specificity of MRI for diagnosis of partial thickness subscapularis tears were 38.1% and 86.5%, respectively, while its accuracy was 72.5%.

Researchers also examined two signs on MRI that are indicative of subscapularis tears viz. cysts within the lesser tuberosity of humerus and subcoracoid cysts. Both the signs had low sensitivity (19.8% and 33.8%) but high specificity (98.2% and 94.6%).

This study shows that preoperative ultrasound had significantly greater sensitivity and specificity than MRI in diagnosing subscapularis tears. According to the authors, USG was also able to diagnose partial thickness tears with greater accuracy in nearly 74% of patients compared to 38% patients diagnosed with MRI. These findings suggest USG as a reliable diagnostic tool in patients with subscapularis tears, in particular the partial thickness tears, which often go undiagnosed. However, it’s prudent to point out here that ultrasound is a highly operator-dependent modality and individual skill affects the results.

Reference

1. Zhu S, et al. Ultrasonography outperforms magnetic resonance imaging in diagnosing partial-thickness subscapularis tear. Arthroscopy. 2022 Feb;38(2):278-284.doi: 10.1016/j.arthro.2021.07.015.