Aim: The aim of the study was to determine the thickness of the tendinous and capsuloligamentous layers in the supraspinatus and infraspinatus zones of the shoulder. Materials and methods: Anatomical and ultrasonographic assessment of three fresh anatomical specimens consisting of the humeral head together with the capsuloligamentous layer called the superior complex and the supraspinatus and infraspinatus myotendinous units cut off at the level of the scapular glenoid rim. The first specimen was dissected on the length of approx. 10 mm from the glenoid insertion – the superior complex insertional zone to the scapula. Distally anterior (coraco-humeral and gleno-humeral superior ligaments) and posterior (gleno-humeral superior posterior ligament) limbs are connected by a transversely oriented ligament called the rotator cuff cable. This structure, together with the rest of the superior complex, belongs to the capsuloligamentous layer of the rotator cuff. The two other specimens were dissected (superior complex from the myotendinous units) from the level of the glenoid rim to the humeral insertion. Then the three specimens were scanned by ultrasound in a water bath and the measurements of both distinct layers were taken. Results: The rotator cuff in the supraspinatus and infraspinatus zone is a two-layer structure. The thickness of the tendinous and the capsuloligamentous layer is comparable. Conclusions: It may be concluded that the rotator cuff in the supraspinatus and infraspinatus zone is a two-layer structure, with the outer myotendinous layer, and the inner capsuloligamentous layer, which is called the superior complex. Since the thickness of these layers is comparable, it is important to bear in mind that the superior complex is an important part of shoulder biomechanics. Two different structures are found here – tendinous (dynamic) and capsuloligamentous (passive).
