The anterior labroligamentous periosteal sleeve avulsion lesion: a cause of anterior instability of the shoulder.

Recurrent anterior unidirectional instability of the shoulder is not always associated with a classic Bankart lesion, which is an avulsion of the anterior labroligamentous structures from the anterior glenoid rim. Because the anterior scapular periosteum ruptures, the labrum and the attached ligaments are found to float out anterior to the glenoid rim when viewed arthroscopically. The anterior labroligamentous periosteal sleeve avulsion (ALPSA) of the supporting anterior inferior ligamentous and labral structures of the shoulder joint was found in four of eight acute primary anterior shoulder dislocations. This lesion differs from the Bankart lesion because the anterior scapular periosteum does not rupture, thereby allowing the labroligamentous structures to displace medially and rotate inferiorly on the scapular neck. These lesions eventually heal, and lead to recurrent anterior dislocations because of the subsequent incompetence of the anterior inferior glenohumeral ligament. An arthroscopic technique that converts the ALPSA lesion to a Bankart lesion and subsequently reconstructs the supporting anterior inferior structures of the shoulder has been successful in 26 cases (4 acute and 22 chronic) which were followed for > or = 2 years. Only one dislocation occurred, and it was the result of severe trauma.