Background 

Knotted and knotless single-anchor reconstruction techniques are frequently performed to reconstruct full-thickness tears of the upper portion of subscapularis tendon. However, it is unclear whether one technique is superior to the other.

Questions/purposes 

(1) When comparing knotless and knotted single-anchor reconstruction techniques in full-thickness tears of the upper subscapularis tendon, is there a difference in stiffness under cyclic load? (2) Are there differences in cyclic gapping between knotless and knotted reconstructions? (3) Are there differences in the maximal stiffness, yield load, and ultimate load to failure? (4) What are the modes of failure of knotless and knotted reconstruction techniques?

Methods 

Eight matched pairs of human cadaveric shoulders were dissected, and a full-thickness tear of the subscapularis tendon (Grade 3 according to the Fox and Romeo classification) was created. The cadavers all were male specimens, with a median (range) age of 69 years (61 to 75). Before biomechanical evaluation, the specimens were randomized into two equal reconstruction groups: knotless single anchor and knotted single anchor. All surgical procedures were performed by a single orthopaedic surgeon who subspecializes in sports orthopedics and shoulder surgery. With a customized set up that was integrated in a dynamic material testing machine, the humeri were consecutively loaded from 10 N to 60 N, from 10 N to 100 N, and from 10 N to 180 N for 50 cycles. Furthermore, the gapping behavior of the tear was analyzed using a video tracking system. Finally, the stiffness, gapping, maximal stiffness, yield loads, and maximum failure loads of both reconstruction groups were statistically analyzed. Failure was defined as retearing of the reconstructed gap threshold due to rupture of the tendon and/or failure of the knots or anchors. After biomechanical testing, bone quality was measured at the footprint of the subscapularis using microCT in all specimens. Bone quality was equal between both groups. To detect a minimum 0.15-mm difference in gap formation between the two repair techniques (with a 5% level of significance; α = 0.05), eight matched pairs (n = 16 in total) were calculated as necessary to achieve a power of at least 90%.

Results 

The first study question can be answered as follows: for stiffness under cyclic load, there were no differences with the numbers available between the knotted and knotless groups at load stages of 10 N to 60 N (32.7 ± 3.5 N/mm versus 34.2 ± 5.6 N/mm, mean difference 1.5 N/mm [95% CI -6.43 to 3.33]; p = 0.55), 10 N to 100 N (45.0 ± 4.8 N/mm versus 45.2 ± 6.0 N/mm, mean difference 0.2 N/mm [95% CI -5.74 to 6.04]; p = 0.95), and 10 N to 180 N (58.2 ± 10.6 N/mm versus 55.2 ± 4.7 N/mm, mean difference 3 N/mm [95% CI -5.84 to 11.79]; p = 0.48). In relation to the second research question, the following results emerged: For cyclic gapping, there were no differences between the knotted and knotless groups at any load levels. The present study was able to show the following with regard to the third research question: Between knotted and knotless repairs, there were no differences in maximal load stiffness (45.3 ± 8.6 N/mm versus 43.5 ± 10.2 N/mm, mean difference 1.8 [95% CI -11.78 to 8.23]; p = 0.71), yield load (425.1 ± 251.4 N versus 379.0 ± 169.4 N, mean difference 46.1 [95% CI -276.02 to 183.72]; p = 0.67), and failure load (521.1 ± 266.2 N versus 475.8 ± 183.3 N, mean difference 45.3 [95% CI -290.42 to 199.79]; p = 0.69). Regarding the fourth question concerning the failure modes, in the knotted repairs, the anchor tore from the bone in 2 of 8, the suture tore from the tendon in 6 of 8, and no suture slipped from the eyelet; in the knotless repairs, the anchor tore from the bone in 2 of 8, the suture tore from the tendon in 3 of 8, and the threads slipped from the eyelet in 3 of 8.

Conclusion 

With the numbers available, we found no differences between single-anchor knotless and knotted reconstruction techniques used to repair full-thickness tears of the upper portion of subscapularis tendon.

Clinical Relevance 

The reconstruction techniques we analyzed showed no differences in terms of their primary stability and biomechanical properties at the time of initial repair and with the numbers available. In view of these experimental results, it would be useful to conduct a clinical study in the future to verify the translationality of the experimental data of the present study.

中文翻译：

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有结或无结技术更适合肩胛下肌腱上部全层撕裂的重建吗？尸体研究

背景 

经常使用有结和无结单锚重建技术来重建肩胛下肌腱上部的全层撕裂。然而，尚不清楚一种技术是否优于另一种技术。

问题/目的 

(1) 比较上肩胛下肌腱全层撕裂的无结和有结单锚重建技术时，循环载荷下的刚度是否存在差异？(2)无结重建和有结重建之间的循环间隙是否存在差异？(3) 最大刚度、屈服载荷和极限失效载荷是否存在差异？(4) 无结和有结重建技术的失败模式是什么？

方法 

解剖了八对匹配的人体尸体肩膀，并产生了肩胛下肌腱的全层撕裂（根据 Fox 和 Romeo 分类为 3 级）。尸体均为男性标本，中位年龄（范围）为 69 岁（61 至 75 岁）。在进行生物力学评估之前，将标本随机分为两个相等的重建组：无结单锚和有结单锚。所有手术均由一位专攻运动骨科和肩部手术的骨科医生完成。通过集成在动态材料测试机中的定制设置，肱骨连续加载 10 N 至 60 N、10 N 至 100 N 以及从 10 N 至 180 N，持续 50 个循环。此外，使用视频跟踪系统分析了撕裂的间隙行为。最后，对两个重建组的刚度、间隙、最大刚度、屈服载荷和最大破坏载荷进行统计分析。失败被定义为由于肌腱断裂和/或结或锚的失败而导致重建间隙阈值的重新撕裂。生物力学测试后，使用 microCT 对所有标本的肩胛下肌足迹进行骨质量测量。两组之间的骨质量相同。为了检测两种修复技术之间间隙形成的最小 0.15 毫米差异（显着性水平为 5%；α = 0.05），根据需要计算了 8 个匹配对（总共 n = 16），以达到至少90%。

结果 

第一个研究问题可以回答如下：对于循环载荷下的刚度，在 10 N 至 60 N 的载荷阶段，有结组和无结组之间的可用数量没有差异（32.7 ± 3.5 N/mm 与 34.2 ± 5.6 N/mm，平均差 1.5 N/mm [95% CI -6.43 至 3.33]；p = 0.55)，10 N 至 100 N（45.0 ± 4.8 N/mm 与 45.2 ± 6.0 N/mm，平均差 0.2 N/ mm [95% CI -5.74 至 6.04]；p = 0.95)，以及 10 N 至 180 N（58.2 ± 10.6 N/mm 与 55.2 ± 4.7 N/mm，平均差 3 N/mm [95% CI -5.84 至11.79]；p = 0.48）。关于第二个研究问题，出现了以下结果：对于循环间隙，在任何负载水平下，有结组和无结组之间没有差异。本研究能够就第三个研究问题表明以下内容：在有结修复和无结修复之间，最大负载刚度没有差异（45.3 ± 8.6 N/mm 与 43.5 ± 10.2 N/mm，平均差异 1.8 [ 95% CI -11.78 至 8.23]；p = 0.71），屈服载荷（425.1 ± 251.4 N 与 379.0 ± 169.4 N，平均差 46.1 [95% CI -276.02 至 183.72]；p = 0.67）和失效载荷（521.1） ± 266.2 N 与 475.8 ± 183.3 N，平均差 45.3 [95% CI -290.42 至 199.79]；p = 0.69）。关于第四个问题，关于失效模式，在打结修复中，8例中有2例是锚钉从骨头上撕裂，8例中有6例是缝合线从肌腱上撕裂，并且没有缝线从孔眼中滑落；在无结修复中，8 例中有 2 例锚钉从骨头上撕裂，8 例中有 3 例缝合线从肌腱撕裂，8 例中有 3 例线从孔眼滑落。

结论 

根据现有数据，我们发现用于修复肩胛下肌腱上部全层撕裂的单锚无结重建技术和有结重建技术之间没有差异。

临床相关性 

我们分析的重建技术在初始修复时的初始稳定性和生物力学特性以及可用的数量方面没有差异。鉴于这些实验结果，未来进行临床研究以验证本研究实验数据的转化性将是有用的。