Chan Kevin, Langohr G Daniel G, Welsh Mark, Johnson James A, Athwal George S
Roth/McFarlane Hand and Upper Limb Centre, St Joseph's Health Care, University of Western Ontario, London, ON, Canada.
JSES Int. 2020 Dec 11;5(2):277-281. doi: 10.1016/j.jseint.2020.10.013. eCollection 2021 Mar.
The optimal insertion location of a latissimus dorsi tendon transfer to restore external rotation after reverse shoulder arthroplasty (RSA) is not well established. The aim of this biomechanical study was to determine the effect of tendon transfer location on external rotation torque, in conjunction with varying RSA humeral component lateralization. We hypothesized that proximal tendon transfers, along with increasing humeral lateralization, would maximize external rotation torque.
Eight fresh-frozen cadaveric shoulders underwent RSA and were tested on an in vitro shoulder simulator. A latissimus dorsi tendon transfer was tested at three insertion locations (lateral greater tuberosity [Lat-GT]; teres minor footprint [Tm-FP]; lateral shaft [Lat-Shft]), and external rotation torque was measured. Additional test conditions included varying humeral component lateralization (-5, 0, +5, +10, +15 mm), abduction angle (0°, 45°, 90°), and internal/external rotation (-60°, -30°, 0°, 30°, 60°).
The Lat-GT and Tm-FP insertions of the latissimus dorsi transfer both generated significantly greater torques ( < .001) than the Lat-Shft. When comparing Lat-GT to Tm-FP, there were no significant differences ( = .362). At 60˚ of external rotation, RSA humeral component lateralization from -5 to +15 mm significantly increased the external rotation torque of Lat-GT by 67% ( = .035), Tm-FP by 43% ( = .001), and of Lat-Shft by 42% ( = .002).
Latissimus dorsi tendon transfer to the proximal lateral aspect of the greater tuberosity and to the insertion site of the teres minor generated significantly more external rotation torque than transfer to the lateral humeral shaft. In addition, the use of a humeral component with greater offset also substantially increases the torque generated by the tendon transfer.
背阔肌肌腱转移术在反肩关节置换术（RSA）后恢复外旋功能时的最佳植入位置尚未明确。本生物力学研究的目的是结合不同的RSA肱骨组件外偏情况，确定肌腱转移位置对外旋扭矩的影响。我们假设近端肌腱转移术，连同增加肱骨外偏，将使外旋扭矩最大化。
对八个新鲜冷冻尸体肩关节进行RSA手术，并在体外肩关节模拟器上进行测试。在三个植入位置（大结节外侧[Lat-GT]；小圆肌足迹[Tm-FP]；肱骨外侧骨干[Lat-Shft]）测试背阔肌肌腱转移术，并测量外旋扭矩。其他测试条件包括改变肱骨组件外偏（-5、0、+5、+10、+15毫米）、外展角度（0°、45°、90°）以及内/外旋（-60°、-30°、0°、30°、60°）。
背阔肌转移至Lat-GT和Tm-FP植入点产生的扭矩均显著大于Lat-Shft植入点（<0.001）。比较Lat-GT和Tm-FP时，无显著差异（=0.362）。在外旋60°时，RSA肱骨组件外偏从-5毫米至+15毫米显著增加Lat-GT的外旋扭矩67%（=0.035），Tm-FP增加43%（=0.001），Lat-Shft增加42%（=0.002）。
背阔肌肌腱转移至大结节近端外侧和小圆肌插入部位产生的外旋扭矩显著大于转移至肱骨外侧骨干。此外，使用更大偏移量的肱骨组件也会显著增加肌腱转移产生的扭矩。
