Shoulder Bankart lesion with posterior instability: A case report of ultrasound detection.

Minor instability of the shoulder has recently drawn attention as a cause of shoulder pain in athletes. However, it is difficult to correctly diagnose the direction in which the humeral head translates and subluxates, and to clarify the pathology of the instability. We present a case of a 20-year-old male with an unstable shoulder who could not raise his left arm due to pain. Since 6 years prior to the onset of pain, the patient could asymptomatically perform voluntary subluxation, but it was slight and the direction of the subluxation could not be confirmed. On physical examination, the conventional apprehension test and Castagna test were positive, but the jerk test was negative. Imaging studies including arthroscopy showed a Bankart lesion associated with anterior labrum detachment. There was no posterior Bankart lesion. Due to painful anterior shoulder instability, arthroscopic Bankart repair was successfully done; however, 9 months later the patient began experiencing symptomatic subluxation of the shoulder. At this time, the conventional apprehension test and Castagna test were both negative. It was difficult to detect the direction of the subluxation, just like in the preoperative condition. We performed an ultrasonographic examination from the posterior side; this clearly revealed the posterior subluxation mechanism as posterior slide of the humeral head and anterior shift of the glenoid. Based on these findings, we modified the rehabilitation and the subluxation resolved. This case suggests that ultrasound imaging can be an effective practical option for evaluating shoulder instability, especially in cases of slight posterior subluxation.