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Arthroscopic anteroinferior suture plication resulting in decreased glenohumeral translation and external rotation. Study of a cadaver model.

BACKGROUND
The consequences of arthroscopic plication for the treatment of anterior shoulder instability are unknown. The purpose of this study was to evaluate the effects of arthroscopic plication on glenohumeral translation, the rotational range of motion, and the positions of the glenohumeral center of rotation.


METHODS
Six cadaver shoulders were tested in the intact state, after simulation of anterior instability by anterior capsular stretching, after creation of arthroscopic portals, and following a 10-mm anteroinferior arthroscopic suture plication. Capsulolabral build-up was measured to quantify the increase after plication.


RESULTS
Stretching resulted in a significant increase, compared with the intact state, in external rotation (mean increase, 23.2 degrees [14.3%]; p < 0.001) but not in glenohumeral translation (mean increase, 0.8 mm [7.4%] under a 20-N translational load; p = 0.06). After plication, external rotation decreased significantly (by 12.6 degrees [6.7%], p = 0.003) compared with that following the stretching. After plication, the glenohumeral center of rotation was significantly shifted posteriorly at 60 degrees , 90 degrees , and 120 degrees of external rotation and inferiorly at 90 degrees and 120 degrees . Plication also resulted in significant decreases in anterior translation (mean decrease, 61.1% under a 15-N translational load and 49.8% under a 20-N translational load; p < 0.001), posterior translation (mean decrease, 11.4% under a 15-N translational load and 13.1% under a 20-N translational load; p = 0.002 and p < 0.001, respectively), and inferior translation (mean decrease, 3.2% under a 20-N load; p = 0.04). The height of the capsulolabral "bumper" increased from 2.9 mm in the intact state to 6.4 mm following plication (p = 0.001).


CONCLUSIONS
Arthroscopic anteroinferior plication effectively reduces anterior translation and external rotation. Capsulolabral buildup may help limit anterior translation without affecting rotation. Plication resulted in a shift of the glenohumeral center of rotation posteriorly and inferiorly.