School of Precision and Biomedical Engineering, University of Bern, Bern, Switzerland; Institute for Biomechanics, ETH Zürich, Zürich, Switzerland.
Shoulder, Elbow and Orthopaedic Sports Medicine, Orthopaedics Sonnenhof, Bern, Switzerland; Department of Orthopaedics and Trauma Surgery, Hospital San José-Clínica Santa María, Santiago, Chile.
J Shoulder Elbow Surg. 2024 Dec;33(12):2586-2595. doi: 10.1016/j.jse.2024.03.019. Epub 2024 Apr 19.
Tendon transfers are established techniques to regain external rotation mobility in patients with an irreparable, posterosuperior massive rotator cuff tear (MRCT). Posterosuperior MRCT with intact teres minor (type D MRCT) can lead to excessive teres minor loading to maintain external rotation. We hypothesize that tendon transfers are effective in relieving teres minor loading in type D MRCTs. Our aim was to biomechanically assess muscle synergism with latissimus dorsi (LD transfer) and lower trapezius (LT transfer) tendon transfer during external rotation at different abduction heights.
Using musculoskeletal modeling, we analyzed and compared the moment arm, muscle torque, and muscle activity between a healthy and type D MRCT pathologic model with and without the LD- or LT transfer at infraspinatus and teres minor insertion sites. Output measures were analyzed during external rotation at different abduction angles and 10-50 N resistance against external rotation. We assessed its impact on teres minor loading in a type D MRCT. Morphologic variations were parameterized using the critical shoulder angle and the acromiohumeral distance to address variations among patients.
Both transfer types reduced teres minor torque and activity significantly, reaching physiological state at 40 N external resistance (P < .001), with insertion to infraspinatus site being more effective than teres minor site (P < .001). External rotation moment arms of LD transfer were larger than LT transfer at 90° abduction (25.1 ± 0.8 mm vs. 21.2 ± 0.6 mm, P < .001) and vice versa at 0° abduction (17.4 ± 0.5 mm vs. 24.0 ± 0.2 mm, P < .001). Although the healthy infraspinatus was the main external rotator in all abduction angles (50%-70% torque), a type D MRCT resulted in a 70%-90% increase of teres minor torque and an up to 7-fold increase in its activity leading to excessive loadings beyond 10 N resistance against external rotation. Varying the critical shoulder angle and the acromiohumeral distance led to minor variations in muscle moment arm and muscle activity.
We identified biomechanical efficacy of both tendon transfers in type D MRCT regarding teres minor load relief and superior performance of the transfers at the infraspinatus insertion site.
对于无法修复的后上方巨大肩袖撕裂（MRCT）患者，肌腱转位是恢复外旋活动度的成熟技术。伴有小菱形肌完整的后上方 MRCT（D 型 MRCT）可导致小菱形肌过度负荷以维持外旋。我们假设肌腱转位对于 D 型 MRCT 中小菱形肌的负荷减轻是有效的。我们的目的是通过生物力学评估 Latissimus dorsi（LD 转移）和 Lower trapezius（LT 转移）肌腱转移在外展不同高度时的外旋中的肌肉协同作用。
使用肌肉骨骼建模，我们分析并比较了健康模型和 D 型 MRCT 病理模型在冈下肌和小菱形肌插入部位有无 LD 或 LT 转移时，在不同外展角度和 10-50 N 外旋阻力下的力臂、肌肉扭矩和肌肉活动。我们在外展角度为 0°和 90°时评估了其对 D 型 MRCT 中小菱形肌负荷的影响。使用临界肩角和肩峰肱骨距离对形态学变异进行参数化，以解决患者之间的变异。
两种转移类型均显著降低小菱形肌扭矩和活动，在 40 N 外旋阻力下达到生理状态（P<.001），冈下肌插入部位比小菱形肌插入部位更有效（P<.001）。在 90°外展时，LD 转移的外旋力臂大于 LT 转移（25.1±0.8 mm 比 21.2±0.6 mm，P<.001），而在 0°外展时则相反（17.4±0.5 mm 比 24.0±0.2 mm，P<.001）。尽管在所有外展角度下（50%-70%的扭矩），健康的冈下肌都是主要的外旋肌，但 D 型 MRCT 导致小菱形肌扭矩增加 70%-90%，其活动增加 7 倍以上，导致超过 10 N 外旋阻力的过度负荷。临界肩角和肩峰肱骨距离的变化导致肌肉力臂和肌肉活动的微小变化。
我们确定了 D 型 MRCT 中小菱形肌负荷减轻方面两种肌腱转移的生物力学效果，以及冈下肌插入部位转移的优越性能。
