Mihata Teruhisa, Gates Jeffrey, McGarry Michelle H, Neo Masashi, Lee Thay Q
Department of Orthopedic Surgery, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki, Osaka, 569-8686, Japan,
Knee Surg Sports Traumatol Arthrosc. 2015 Feb;23(2):548-54. doi: 10.1007/s00167-013-2381-7. Epub 2013 Jan 16.
Posterior shoulder tightness is common in throwing athletes, especially those with symptomatic shoulder internal impingement. The role of posteroinferior capsular contracture in the pathoetiologies of throwing-related injuries caused by shoulder internal impingement remains unclear. The purpose of this study was to assess effect of posterior shoulder tightness on internal impingement in a cadaveric model of throwing.
Seven fresh-frozen cadaveric shoulders were tested with the shoulder abducted to 90° and at maximum external rotation to simulate the late cocking phase of throwing motion. Glenohumeral joint contact pressure and area through internal impingement, humeral head shift, and the maximum humeral rotation angle were measured. Posteroinferior capsular plication was performed to simulate posteroinferior capsular tightness and induce glenohumeral internal rotation deficit.
Following generation of simulated posteroinferior capsular tightness with resultant glenohumeral internal rotation deficit, glenohumeral contact pressure was significantly increased (P < 0.05), the impinged area of rotator cuff tendon was significantly decreased (P < 0.05), and the humeral head shifted posteriorly (P < 0.05) during shoulder internal impingement.
Excessive posteroinferior capsular tightness can cause forceful internal impingement of the shoulder at maximum external rotation position.
后肩部紧张在投掷运动员中很常见，尤其是那些有症状性肩部内撞击的运动员。后下关节囊挛缩在肩部内撞击引起的与投掷相关损伤的病理病因中的作用仍不清楚。本研究的目的是在一个投掷尸体模型中评估后肩部紧张对肩部内撞击的影响。
对七个新鲜冷冻的尸体肩部进行测试，将肩部外展至90°并处于最大外旋位，以模拟投掷动作的晚期引臂阶段。测量通过内撞击时的盂肱关节接触压力和面积、肱骨头移位以及最大肱骨旋转角度。进行后下关节囊折叠以模拟后下关节囊紧张并诱发盂肱关节内旋不足。
在产生模拟的后下关节囊紧张并导致盂肱关节内旋不足后，在肩部内撞击期间，盂肱关节接触压力显著增加（P < 0.05），肩袖肌腱的撞击面积显著减小（P < 0.05），肱骨头向后移位（P < 0.05）。
后下关节囊过度紧张可导致肩部在最大外旋位时发生强力内撞击。
