Belotti Natalia, Fox Aaron S, Henze Janina, Page Richard S, Ernstbrunner Lukas, Ackland David C
University of Melbourne, Melbourne, Australia.
Deakin University, Geelong, Australia.
Orthop J Sports Med. 2025 Apr 14;13(4):23259671251329516. doi: 10.1177/23259671251329516. eCollection 2025 Apr.
Splitting the subscapularis in the Latarjet procedure is known to influence subscapularis muscle mechanics postoperatively; however, the influence of split level on postoperative muscle and joint function remains poorly understood.
To assess the effects of midlevel, lower-third, and upper-third subscapularis split levels in the Latarjet procedure on subscapularis lines of action and moment arms in the shoulder abduction, abduction and external rotation (ABER), and apprehension positions.
Controlled laboratory study.
The Latarjet procedure was performed on 8 fresh-frozen human cadaveric upper extremities with a simulated 20% anteroinferior glenoid bone defect. A midwidth subscapularis muscle belly split was first performed on all specimens in which the conjoint tendon was routed. Lines of action and moment arms of 4 subregions of the subscapularis muscle (superior, mid-superior, mid-inferior, and inferior) were quantified radiographically with the conjoint tendon unloaded and loaded and the glenohumeral joint positioned in (1) 0° of abduction, (2) 90° of abduction, (3) 90° of abduction and full external rotation (ABER), and (4) the apprehension position, defined as ABER with 30° of horizontal extension. Testing was then repeated in random order after rerouting the conjoint tendon through both an upper- and then lower-third subscapularis split. Utmost care was taken to ensure that the subscapularis muscle integrity was not disrupted during the rerouting process.
Subscapularis splitting in Latarjet surgery deformed the muscle fibers below the split level, significantly increasing the inferior inclination of subscapularis muscle lines of action, but only for the midlevel and lower-third subscapularis split levels ( < .001). This increased inferior inclination was significantly greater in the ABER and apprehension positions compared with those at 0° and 90° of abduction ( < .05). In the ABER and apprehension positions, the adduction moment arms of the mid-superior subscapularis muscle subregion were also significantly larger for the midlevel split compared with the lower-third and upper-third split ( < .05), indicating greater depressor capacity.
Latarjet surgery deforms subscapularis muscle fibers below the level of the split, changing subscapularis leverage and line of force. The midlevel subscapularis muscle split in the Latarjet procedure confers greater mechanical advantage in terms of shoulder depressor function and stabilizing potential than that associated with an upper-third or lower-third split, particularly in the ABER and apprehension positions.
Subscapularis muscle leverage and force potential are significantly influenced by split location in Latarjet surgery. A midlevel subscapularis split is likely to provide the greatest mechanical stability, particularly in positions of shoulder instability.
已知在Latarjet手术中劈开肩胛下肌会影响术后肩胛下肌的力学功能；然而，劈开水平对术后肌肉和关节功能的影响仍知之甚少。
评估Latarjet手术中肩胛下肌中部、下三分之一和上三分之一劈开水平对肩胛下肌在肩关节外展、外展和外旋（ABER）以及恐惧试验位时的作用线和力臂的影响。
对照实验室研究。
对8具新鲜冷冻的人体尸体上肢进行Latarjet手术，模拟20%的前下盂肱关节骨缺损。首先在所有标本上进行中宽的肩胛下肌肌腹劈开，然后将联合腱穿过劈开处。在联合腱卸载和加载且盂肱关节处于以下位置时，通过影像学定量分析肩胛下肌4个亚区域（上部、中上、中下和下部）的作用线和力臂：（1）外展0°；（2）外展90°；（3）外展90°且完全外旋（ABER）；（4）恐惧试验位，定义为外展90°且水平伸展30°的ABER位。然后在联合腱依次穿过肩胛下肌上三分之一和下三分之一劈开处后，以随机顺序重复测试。在重新穿线过程中，尽最大努力确保肩胛下肌的完整性未受到破坏。
Latarjet手术中劈开肩胛下肌使劈开水平以下的肌纤维变形，显著增加了肩胛下肌作用线的下倾角度，但仅在肩胛下肌中部和下三分之一劈开水平时出现这种情况（P<0.001）。与外展0°和90°时相比，在ABER和恐惧试验位时，这种增加的下倾角度明显更大（P<0.05）。在ABER和恐惧试验位时，肩胛下肌中上亚区域的内收力臂在中部劈开时也显著大于下三分之一和上三分之一劈开时（P<0.05），表明其下压能力更强。
Latarjet手术使劈开水平以下的肩胛下肌纤维变形，改变了肩胛下肌的杠杆作用和力的方向。Latarjet手术中肩胛下肌中部劈开在肩关节下压功能和稳定潜力方面比上三分之一或下三分之一劈开具有更大的机械优势，尤其是在ABER和恐惧试验位时。
Latarjet手术中劈开位置对肩胛下肌的杠杆作用和力的潜力有显著影响。肩胛下肌中部劈开可能提供最大的机械稳定性，尤其是在肩关节不稳定的位置。
