Among the types of glenoid labral tear, it has been shown that the posterosuperior(PS) labral tear can occur in both athletes and non-athletes using overhead throwing motion with posterosuperior impingement or having tension overload in the rotator cuff and repetitive shearing of the humeral head against the PS labrum. For the definite diagnosis of PS labral tear, arthroscopy, arthrography, or magnetic resonance imaging(MRI) are usually required. However, in recent studies, the ultrasound(US) arthrosonography has been reported as one of useful method to diagnose PS labral tear.
In addition to conventional US scanning of shoulder labrum, we propose a novel method for dynamic evaluation of the PS labral tear. When examining the PS labrum with US, a high-frequency(5-12 MHz) linear probe is used, with the patient sitting down in front of the examiner. First, the conventional US scanning of PS labrum, with the patient’s arm passively adducted and internally rotated with the elbow flexion of 90 degrees, is done. Than a dynamic examination is performed by abducting and externally rotating the arm, passively. The humeral head is rotated externally when the arm is passively abducted and external rotated, which gives stress to the PS labrum(ABER stress test). In a normal PS labrum, there would not be any significant finding(Figure 1). However, in injured PS labrum, this stress may cause posterior and medial detachment of the labrum, or joint fluid leakage through the torn PS labrum(Figure 2). |
