Mihata Teruhisa, McGarry Michelle H, Tibone James E, Fitzpatrick Michael J, Kinoshita Mitsuo, Lee Thay Q
Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, 5901 East 7th Street, Long Beach, CA 90822, USA.
Am J Sports Med. 2008 Aug;36(8):1604-10. doi: 10.1177/0363546508315198. Epub 2008 Mar 21.
Type II superior labral anterior-posterior lesions in throwers are often associated with anterior shoulder capsular laxity.
Shoulder 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.
Controlled laboratory study.
Six 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.
The 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).
Because 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.
Anterior 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.
投掷运动员的Ⅱ型上盂唇前后部损伤常与肩关节前囊松弛相关。
Ⅱ型上盂唇前后部损伤患者的肩部不稳定可能是由相关的肩关节囊松弛导致，而非仅由上盂唇前后部损伤引起。
对照实验室研究。
六具尸体肩关节在肱盂外展60度时，外旋至超过肱骨最大外旋角度20%，模拟90度肩关节外展，以分离上盂唇并延长肩关节前囊韧带。然后修复分离的盂唇，以分离分离的上盂唇和关节囊松弛的影响。在肱盂外展60度时测量旋转活动范围。在肱盂外展30度和60度时测量肱盂前后向平移。在肱盂外展0度和60度时测量肱盂上下向平移。
实验造成的Ⅱ型上盂唇前后部损伤和关节囊松弛显著增加了肱盂外展30度（平均差异，1.0±0.8毫米；P<.05）和60度（平均差异，2.2±2.0毫米；P<.05）时的前向平移。随后的上盂唇前后部修复恢复了前向平移，但仅在肱盂外展30度时（平均差异，0.9±0.6毫米；P<.05）。
由于Ⅱ型上盂唇前后部损伤相关的前囊松弛，剥离的上盂唇的上盂唇前后部修复可能无法恢复肩关节外展90度时的肱盂前向平移。
Ⅱ型上盂唇前后部损伤相关的肩关节前囊松弛可能导致投掷运动员在肩关节外展90度时出现肩关节前不稳定，即使在上盂唇前后部损伤修复后也是如此。
