Department of Trauma-, Hand- and Reconstructive Surgery, Wilhelms University Muenster, Muenster, Germany,
Arch Orthop Trauma Surg. 2011 Aug;131(8):1159-65. doi: 10.1007/s00402-011-1331-4. Epub 2011 Jun 11.
Double-bundle reconstruction of the ACL has become the focus of scientific and clinical interest in the last years. However, there is still a discussion about the most appropriate technique for graft fixation. Both, extracortical fixation systems like the Endobutton and aperture fixation by interference screws have advantages as well as disadvantages. Aim of this study was to analyze the biomechanical properties of a new small wedge shaped implant (MiniShim, Karl Storz, Germany) for the fixation of a soft tissue graft in double bundle ACL reconstruction and to compare it to an aperture fixation by interference screw and an extracortical fixation.
Porcine knees and flexor tendons were used for this study. 5 and 6 mm tunnels were drilled. The following fixation strategies were tested: 4 and 5 mm MiniShim (Karl Storz Germany), 6 mm interference screw (MegaFix, Karl Storz, Germany), hybridfixation by FlippTack (FlippTack, Karl Storz, Germany) and MiniShim and hybridfixation by FlippTack and 6 mm interference screw. All fixation strategies were tested with a 5 and 6 mm tendon graft. Maximum load, yield load and stiffness were recorded using a material testing machine. Load was applied in line with the bone tunnel. Grafts were cyclically preconditioned between 0 and 20 N for 10 cycles before the graft-bone-complex was loaded to failure. Statistical evaluation was performed using SPSS Version 11.0.
Load to failure for the 5 mm graft was 81.1 and 118.0 N for the 4 and 5 mm MiniShims. Fixation by interference screw reached 237.4 N. The extracortical fixation resulted in a load to failure of 471.7 N. Load to failure for the 6 mm tendon grafts was 52.0 and 92.8 N for the 4 and 5 mm MiniShims. Fixation by interference screw resulted in a load to failure of 214.0 N. Extracortical fixation failed at 451.7 N. The difference between MiniShim and interference screw was statistically significant. Load to failure was significantly higher for extracortical fixation compared to fixation by MiniShim or interference screw. Hybrid fixation showed higher fixation strength compared to fixation by interference screw or MiniShim alone. This difference was statistically significant. Stiffness was significantly higher for fixation by interference screw compared to extracortical fixation and fixation by MiniShim. Four different modes of failure could be seen. All 4 mm MiniShims failed by slippage of the tendon past the MiniShim. In the 5 mm group the fixation failed by pullout of the MiniShim or the tendon past the MiniShim. Hybrid fixation failed by rupture of the linkage material. When the graft was fixed by an interference screw failure occurred by rupture of the tendon at the fixation side.
Hybrid fixation using the MiniShim provides biomechanical properties strong enough to withstand the forces occurring during rehabilitation and comparable to the fixation strength provided by interference screw. While fixation by MiniShim alone does not provide sufficient fixation strength in double bundle ACL reconstruction, hybridfixation using a cortical fixation by FlippTack is an alternative to aperture fixation by interference screw concerning primary stability.
在过去的几年中，ACL 的双束重建已成为科学和临床关注的焦点。然而，对于最合适的移植物固定技术仍存在争议。皮质外固定系统（如 Endobutton）和干扰螺钉的孔径固定都有其优缺点。本研究的目的是分析一种新的小楔形植入物（MiniShim，Karl Storz，德国）在双束 ACL 重建中固定软组织移植物的生物力学特性，并将其与孔径固定的干扰螺钉和皮质外固定进行比较。
本研究使用猪膝关节和屈肌腱。钻 5 和 6mm 隧道。测试了以下固定策略：4 和 5mm MiniShim（Karl Storz 德国）、6mm 干扰螺钉（MegaFix，Karl Storz，德国）、FlippTack（FlippTack，Karl Storz，德国）的混合固定以及 MiniShim 和 FlippTack 的混合固定和 6mm 干扰螺钉。所有固定策略均使用 5 和 6mm 肌腱移植物进行测试。使用材料试验机记录最大载荷、屈服载荷和刚度。载荷沿骨隧道施加。在将移植物-骨复合物加载至失效之前，将移植物进行 0 至 20N 的循环预加载 10 个循环。使用 SPSS 版本 11.0 进行统计评估。
5mm 移植物的失效载荷为 4 和 5mm MiniShim 的 81.1 和 118.0N。干扰螺钉固定达到 237.4N。皮质外固定的失效载荷为 471.7N。6mm 移植物的失效载荷为 4 和 5mm MiniShim 的 52.0 和 92.8N。干扰螺钉固定的失效载荷为 214.0N。皮质外固定失效于 451.7N。MiniShim 和干扰螺钉之间的差异具有统计学意义。与皮质外固定或 MiniShim 固定相比，失效载荷显著更高。混合固定与单独使用干扰螺钉或 MiniShim 固定相比，固定强度更高。这种差异具有统计学意义。与皮质外固定和 MiniShim 固定相比，干扰螺钉固定的刚度显著更高。可以看到四种不同的失效模式。所有 4mm MiniShim 均因肌腱滑过 MiniShim 而失效。在 5mm 组中，固定失败是由于 MiniShim 或肌腱滑过 MiniShim 而导致的。混合固定是由于连接材料的断裂而失效。当移植物用干扰螺钉固定时，失效是由于固定侧的肌腱断裂引起的。
使用 MiniShim 的混合固定提供了足够强大的生物力学特性，可以承受康复过程中产生的力，并且与干扰螺钉提供的固定强度相当。虽然单独使用 MiniShim 固定在双束 ACL 重建中不能提供足够的固定强度，但使用 FlippTack 的皮质固定的混合固定是孔径固定的干扰螺钉的替代方案，考虑到初始稳定性。
