Analysis of Posterior Shoulder Instability


Over the past decade, all-arthroscopic techniques have become an accepted method of performing both anterior and posterior shoulder stabilization procedures, with results comparable with and sometimes better than open procedures. Furthermore, even though there is a high association between anterior capsular laxity and Bankart lesions, there is no consensus on the association between posterior capsular laxity and the so-called reverse Bankart lesion. Regardless of the cause, the factor most commonly associated with posterior shoulder instability is thought to be laxity of the posterior capsule, and thus treatment has been focused on reducing posterior capsular redundancy via capsular plication in an attempt to restore stability to the shoulder. In addition, capsular plication of the posteroinferior (PI) quadrant of the glenoid is also used to augment stabilization of a concomitant anterior labral repair or in cases of excessive anterior instability without any appreciable labral tear.

Although it is well known that capsular stitches hold well in the labrum and anterior capsule, the posterior capsule is thinner, less robust biomechanically, and may not provide an optimal fixation construct.5 When addressing laxity, the goal of plication is to arthroscopically create a fold in the capsular tissue, thereby reducing the redundancy created by excessive stretch and/or pull on the capsule. Several methods of capsular plication to the PI quadrant are in current clinical use, and several outcome studies describe results of plication; however, no studies in the literature to date compare the biomechanical properties of several different plication techniques to the PI quadrant of the glenohumeral capsule.

The purpose of the present shoulder surgery study was to determine the clinically relevant biomechanical properties (mode of failure, ultimate load to failure, load at 2 mm of displacement, as well as displacement) of suture plication of the PI quadrant of the glenoid, performed using various plication repair constructs to an intact labrum. Specifically, repairs with simple stitch configuration, horizontal mattress configuration, and figure-of-8 configuration were compared. Our null hypothesis was that there would be no biomechanical differences between the different repair constructs.

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