Biomechanical evaluation after five and ten millimeter anterior glenohumeral capsulorrhaphy using a novel shoulder model of increased laxity

Anterior instability of the shoulder is classically treated with a capsulolabral repair, but in cases of capsular redundancy, shortening or shifting of the capsule is added. This study compared glenohumeral translations in intact shoulders after rotational stretching of the capsule and after progressive increasing of anterior-inferior capsular shifts. Seven cadaveric shoulders were mounted on a custom biomechanical testing apparatus. Rotational range of motion and glenohumeral translations were measured. To create laxity, the shoulders were rotationally stretched an additional 30% from the intact rotational range of motion about the axis of the humerus in external and internal rotation. Anterior-inferior capsular shifts of 5 and 10 mm were performed. Rotational stretching of the shoulder capsule created anterior laxity. A 5 mm capsular shift was ineffective, but a 10 mm shift restored anterior and total anteroposterior translation to the intact condition.