【原】一种新型“锁定螺钉”固定技术，看看是什么原理？

锁定螺钉及接骨板可以达到骨折断端有效固定，但该锁定结构的固定强度在骨折愈合过程中并不会发生改变。国外学者研究出一种可变的锁定螺钉，可实现在骨折愈合中产生应力改变，以促进骨折二期愈合。上述研究结果发表在2020.10 JBJS期刊上。

Background

一种新的锁定螺钉技术——“可变固定锁定螺钉（Biomech Innovations）技术（VFLS）” ，旨在促进骨折二期愈合。VFLS具有可再吸收的套管，在骨折愈合期间可逐渐降低其机械性能和体积。在本研究中，我们研究了VLFS是否可以提供与渐进动态固定一样的刚度。

[Background: A new locking-screw technology, the Variable Fixation Locking Screw (VFLS; Biomech Innovations), was developed with the aim of promoting secondary fracture-healing. The VFLS features a resorbable sleeve that progressively decreases its mechanical properties and mass during the fracture-healing time. In this study, we investigated whether the VFLS can provide rigid as well as progressive dynamic fixation.]

Methods

在模拟的骨折间隙模型中测试VFLS提供的骨折间稳定性，并与标准锁定或标准与VFLS两者结合在压缩和扭转载荷下的稳定性比较。测试是在完整的VFLS套管(初始条件)和化学溶解后进行的。一个光学测量系统被用来表征骨块间的运动。

[Methods: The interfragmentary stability provided by the VFLS was tested in a simulated fracture-gap model and compared with that provided by standard locking or by a combination of both technologies under compression and torsional loading. Tests were performed with an intact sleeve (initial condition) and after its chemical dissolution. An optical measurement system was used to characterize interfragmentary movements.]

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▲图1：VFLS螺钉置入皮质骨的模式图。

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图2：测试5个实验组在锁定钢板（黄色）和螺钉固定下轴向与旋转的稳定性（绿色为锁定螺钉，蓝色为VFLS螺钉）：LS（左），VFLS3和VFLS6含有套管；同样的VFLS化学溶解套管（VFLS3ns和VFLS6ns）。

图3：实验模型的制备

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图4：光学测量仪器设备

Results

在初始条件下，各组之间的轴向刚度没有显着差异。套管吸收后显著降低了结构刚度。与对照组相比，VFLS样本用光学测量仪器测量的扭转刚度较低。套管的退化导致近侧皮质和对侧皮质轴向位移均显著增加。在采用组合技术的样本中，近侧皮质增加了约12%至20%，对侧皮质增加了约50%至60%。在仅采用VFLS技术的样本中，对侧皮层的增加约为20%至37%，近侧皮层的增加约为70%至125%。

[Results: The axial stiffness did not differ significantly among groups in the initial condition. Sleeve resorption significantly decreased construct stiffness. The torsional stiffness of the samples instrumented with the VFLS was lower than that of the control group. The degradation of the sleeve resulted in a significant increase in axial displacement recorded at both the cis and trans cortices. In samples featuring combined technologies, this increase was about 12% to 20% at the trans cortex and about 50% to 60% at the cis cortex. In samples featuring VFLS technology only, this increase was about 20% to 37% at the trans cortex and about 70% to 125% at the cis cortex.]

图5：轴向刚度比较。灰色框表示无统计学差异。

图6：扭转刚度对比。

图7：近侧皮质与对侧皮质移位对比。

Conclusions

VFLS提供的初始稳定性等同于标准锁定螺钉技术。可降解套筒的吸收导致有效且可重复的骨折间隙动力化，逐渐改变骨折间隙的应变方式和应变幅度。

[Conclusions: The initial stability offered by the VFLS is equivalent to that of standard locking-screw technology. The resorption of the degradable sleeve leads to effective and reproducible fracture-gap dynamization, progressively varying the way the fracture gap is strained and the magnitude of the strain.]

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