[Normal anatomy and pathological conditions of subscapular muscle: US findings compared with surgery]

Abstract

Purpose: To compare US results with those of surgery in the assessment of the subscapularis tendon.

Material and methods: From January 1995 to December 1998 1500 patients underwent US of the shoulder. 12 of these patients had an injured subscapularis tendon. US results of these patients were evaluated retrospectively and compared with those of surgery. US examinations of the subscapularis tendon were performed with two US units (AU4 Idea and HDI 3000), using linear arrays 10-13 MHz transducers. The following features of the tendon were evaluated: morphology, thickness and echotexture.

Results: A) US findings. US showed: - chronic degenerative tendon changes with diffusely inhomogeneous echotexture (5 cases); - focal tears with small hypoechoic ill-defined areas or gross hypo-anechoic areas involving the full thickness of the tendon (4 cases); - complete tendon tear with disappearance on US of the subscapularis tendon or with severe thickening of the tendon (2 cases); - in 1 case of recent anterior dislocation of the shoulder a bulky hematoma was seen with coexisting thickening and subtotal tear of the tendon. B) Surgical findings. US findings were confirmerd at surgery in 10 of the 12 patients. In the patient with anterior dislocation of shoulder the diagnosis hematoma was confirmed, but the subscapularis tendon was undamaged. Moreover, in 1 out of the 5 patients with US diagnosis of chronic degenerative tendon changes, a small focal tear of the tendon was found at surgery.

Conclusion: US is a first level investigation which is able to demonstrate early changes of the subscapularis tendon and nearby structures. Awareness of pitfalls might decrease the use of second level investigations such as CT arthrography and MR imaging, which on the other hand allow a better definition and assessment of the extent of the injury.