Ilahi Omer A, Younas Shiraz A, Alexander Jerry, Noble Philip C
Texas Arthroscopy and Sports Medicine Institute, Houston, Texas, USA.
Arthroscopy. 2004 Jan;20(1):62-8. doi: 10.1016/j.arthro.2003.11.002.
Arthroscopic soft tissue repairs undergo many cycles of tensioning and relaxation before significant tissue healing occurs, and knot security under cyclic loads is essential for good results after these repairs. The current study was designed to assess the security of arthroscopic knots under stepwise cyclic loading.
In vitro materials testing.
Three types of arthroscopic knots--sliding knots with loop reversal but without post switching (S=SxSxSxS), modified Revo knots with loop reversal and post switching twice (S=S//xSxS//xS), and the SMC knot backed by 2 throws with loop reversal and post switching (S//xS//xS)--were compared with five-throw square knots tied with an open technique. All knots were tied with No. 2 braided nonabsorbable suture around 2 aluminum rods. They were pretensioned to 10 N, and initial displacement was recorded. The knots were then cycled at 1 Hz for 9 different load levels, with 250 cycles at each level, followed by a 30-second rest period to allow recording of permanent laxity of the suture loop. The first step of cyclic loading was from 10 to 40 N, and the upper limit was increased by 10 N for each successive load level. Any knot surviving cyclical loading was pulled to failure.
Ten knots of each configuration were tested. All 3 arthroscopic slip knots showed significantly less initial displacement compared with the square knots (0.26 mm compared with 0.45 mm, respectively, P <.005). All square and modified Revo knots reached the ninth (120 N) loading level, whereas only 6 of the SMC knots and 3 of the arthroscopic knots without post switching reached the ninth loading level. Furthermore, all square and modified Revo knots failed by suture breakage at the knot, whereas 8 arthroscopic knots without post switching and 5 SMC knots failed by slipping. In fact, 3 of the arthroscopic knots without post switching and 1 of the SMC knots failed during the initial cyclic loading from 10 to 40 N. The modified Revo knots reached 3 mm of permanent laxity at significantly higher load levels than the square knots tied with an open technique (96 N v 78 N, P <.005). The SMC knots reached 3 mm of permanent laxity at statistically similar load levels compared with the square knots, but showed considerably more variability. None of the arthroscopic knots without post switching survived the entire cyclic-loading protocol. Four square, 5 modified Revo, and 5 SMC knots that survived cyclic loading reached ultimate failure at statistically similar load levels (157, 156, and 152 N, respectively).
Post switching and loop reversal are key to arthroscopic knot security. Arthroscopic slip knots may be tighter at the time of knot construction than openly hand-tied square knots. The modified Revo knots appear to be as durable as openly hand-tied square knots regarding resistance to loosening under cyclic loading conditions. Security of arthroscopic knots without post switching is quite variable, making these knots less reliable. The SMC knot also proved not to be as reliable as the square and modified Revo knots when cyclically tested.
在显著的组织愈合发生之前，关节镜下软组织修复会经历多次张紧和松弛循环，而循环载荷下的结安全性对于这些修复后的良好效果至关重要。本研究旨在评估逐步循环加载下关节镜结的安全性。
体外材料测试。
将三种类型的关节镜结——无线尾切换的套圈反转滑结（S = SxSxSxS）、套圈反转且线尾切换两次的改良Revo结（S = S//xSxS//xS）以及有两次套圈反转和线尾切换且有2个线尾的SMC结（S//xS//xS）——与开放技术打结的五股方结进行比较。所有结均使用2号编织不可吸收缝线围绕2根铝棒打结。将它们预张紧至10 N，并记录初始位移。然后，结在1 Hz频率下循环9个不同的载荷水平，每个水平循环250次，随后有30秒的休息期以记录缝线环的永久松弛度。循环加载的第一步是从10 N到40 N，每个连续的载荷水平上限增加10 N。任何在循环加载后幸存的结均拉至断裂。
每种构型测试10个结。与方结相比，所有3种关节镜滑结的初始位移均显著更小（分别为0.26 mm和0.45 mm，P <.005）。所有方结和改良Revo结都达到了第九个（120 N）加载水平，而SMC结中只有6个以及无线尾切换的关节镜结中只有3个达到了第九个加载水平。此外，所有方结和改良Revo结均因结处缝线断裂而失效，而8个无线尾切换的关节镜结和5个SMC结因滑动而失效。实际上，3个无线尾切换的关节镜结和1个SMC结在从10 N到40 N的初始循环加载过程中就失效了。改良Revo结在显著高于开放技术打结的方结的载荷水平下达到3 mm的永久松弛度（96 N对78 N，P <.005）。与方结相比，SMC结在统计学上相似的载荷水平下达到3 mm的永久松弛度，但变异性更大。无线尾切换的关节镜结中没有一个在整个循环加载方案中幸存下来。4个方结、5个改良Revo结和5个在循环加载后幸存的SMC结在统计学上相似的载荷水平下达到最终失效（分别为157 N、156 N和152 N）。
线尾切换和套圈反转是关节镜结安全性的关键。关节镜滑结在打结时可能比方结更紧。在循环加载条件下，改良Revo结在抗松弛方面似乎与开放技术打结的方结一样耐用。无线尾切换的关节镜结的安全性差异很大，使得这些结不太可靠。在循环测试时，SMC结也被证明不如方结和改良Revo结可靠。
