• Teruhisa Mihata, Michelle H McGarry, James E Tibone, Michael J Fitzpatrick, Mitsuo Kinoshita, and Thay Q Lee.
• Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, 5901 East 7th Street, Long Beach, CA 90822, USA.
• Am J Sports Med. 2008 Aug 1; 36 (8): 1604-10.

BackgroundType II superior labral anterior-posterior lesions in throwers are often associated with anterior shoulder capsular laxity.HypothesisShoulder instability in patients with type II superior labral anterior-posterior lesions may result from the associated shoulder capsular laxity rather than the superior labral anterior-posterior lesion alone.Study DesignControlled laboratory study.MethodsSix cadaveric shoulders were externally rotated to 20% beyond the maximum humeral external rotation at 60 degrees of glenohumeral abduction, which simulated 90 degrees of shoulder abduction, to detach the superior labrum and elongate the anterior shoulder capsular ligaments. The detached labrum was then repaired to isolate the effect of the detached superior labrum and that of the capsular laxity. Rotational range of motion was measured at 60 degrees of glenohumeral abduction. Anterior-posterior glenohumeral translation was measured at 30 degrees and 60 degrees of glenohumeral abduction. Superior-inferior glenohumeral translation was measured at 0 degrees and 60 degrees of glenohumeral abduction.ResultsThe experimentally created type II superior labral anterior-posterior lesion and capsular laxity significantly increased anterior translation at 30 degrees (mean difference, 1.0 +/- 0.8 mm; P < .05) and 60 degrees (mean difference, 2.2 +/- 2.0 mm; P < .05) of glenohumeral abduction. Subsequent superior labral anterior-posterior repair restored the anterior translation but only at 30 degrees of glenohumeral abduction (mean difference, 0.9 +/- 0.6 mm; P < .05).ConclusionBecause of the anterior capsular laxity associated with type II superior labral anterior-posterior lesions, superior labral anterior-posterior repair of the peeled-back superior labrum may not restore anterior glenohumeral translation at 90 degrees of shoulder abduction.Clinical RelevanceAnterior shoulder capsular laxity associated with type II superior labral anterior-posterior lesions may cause anterior shoulder instability at 90 degrees of shoulder abduction in throwers even after superior labral anterior-posterior lesion repair.

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