AO Foundation, AO Research Institute, Clavadelerstrasse 8, Davos, Switzerland.
Arch Orthop Trauma Surg. 2013 Mar;133(3):373-9. doi: 10.1007/s00402-012-1676-3. Epub 2012 Dec 21.
In trauma surgery, lag screws are commonly used. However, in osteoporotic bone, anchorage can be considerably compromised. This study investigates the biomechanical potential of cement augmentation in terms of improved fixation.
36 Surrogate osteoporotic bone specimens were utilised in three biomechanical experiments, each comparing 6 augmented with 6 non-augmented samples. Standard partially-threaded lag screws (Synthes) were placed following surgical standard. For the augmented groups, 0.4 ml of polymethylmethacrylate was injected into the pre-drilled hole prior to screw placement. Interfragmentary compression was determined using a cannulated ring compression sensor. Maximum torque was recorded with a torque wrench. Compressive relaxation after 24 h, relaxation after loosening and re-tightening the screw as well as maximum compression and torque at failure were measured.
Mean relaxation was significantly lower for the augmented group (p < 0.01). After 24 h, a remaining fragmental compression of 62 % for the augmented and 52 % for the non-augmented specimens was found. Loosening and re-tightening of the screw did not affect the compressive relaxation when augmentation was applied (p = 0.529), compared to an increased relaxation after re-tightening in the non-augmented group (p = 0.04). The mean maximum compression and torque until failure were significantly higher for the augmented group (p < 0.001).
Cement augmentation of lag screws can improve fixation stability in terms of installing and maintaining interfragmentary compression. Effects of relaxation can be reduced and re-tightening of screws is possible without compromising the fixation. Particularly in reduced bone mass, augmentation of lag screws can markedly increase the security of the technique.
在创伤外科中，常使用拉力螺钉。然而，在骨质疏松的骨骼中，固定的效果会大打折扣。本研究旨在探讨骨水泥强化固定在改善固定效果方面的生物力学潜力。
在三个生物力学实验中，共使用了 36 个骨质疏松模拟骨标本，每个实验均比较了 6 个增强组和 6 个非增强组的样本。采用标准部分螺纹拉力螺钉（Synthes），按照手术标准进行固定。对于增强组，在预钻孔中注射 0.4ml 的聚甲基丙烯酸甲酯（PMMA），然后再拧入螺钉。使用带环压缩传感器测定骨折块间的压缩力。使用扭矩扳手记录最大扭矩。测量螺钉松动后重新拧紧 24 小时后的压缩松弛、螺钉松动后的松弛以及最大压缩力和失效扭矩。
增强组的平均松弛率显著低于非增强组（p<0.01）。24 小时后，增强组的骨折块间残余压缩率为 62%，而非增强组为 52%。当应用骨水泥增强时，螺钉的松动和重新拧紧不会影响压缩松弛（p=0.529），而在非增强组中，重新拧紧后会导致松弛增加（p=0.04）。增强组的最大压缩力和失效扭矩显著高于非增强组（p<0.001）。
在拉力螺钉中应用骨水泥增强可以提高固定的稳定性，从而维持骨折块间的压缩。可以减少松弛的影响，并且可以重新拧紧螺钉而不会影响固定效果。在骨量减少的情况下，增强拉力螺钉可以显著提高该技术的安全性。
