Schuller-Götzburg P, Krenkel C, Reiter T J, Plenk H
Department of Oral- and Maxillofacial Surgery, Histological-Embryological Institute, University of Vienna, LKA-Salzburg, Austria.
J Biomech. 1999 May;32(5):511-20. doi: 10.1016/s0021-9290(98)00156-0.
For osteosynthesis and for bone transplant fixation in particular, a lag screw with a biconcave washer, the so called "Anchor Screw" (AS) has been introduced in maxillo-facial surgery. Using 2D-finite element analysis (FEA), the v. Mises and the circumferential stresses induced in underlying bone by this AS are analysed and compared to those under a conventional lag screw. The stress distributions below the biconcave washer of the AS were correlated with histomorphological bone reactions after AS osteosynthesis in two tumor patients, retrieved 12 weeks and 19 months after tumor surgery, respectively. Depending on the thickness of cortical bone, the v. Mises stress concentrations below the biconcave washer were lower than under the head of the conventional lag screw (CLS), but with a higher stress maximum concentrated around the rim of the washer. The circumferential stresses were only half as high around the AS, and thus the deformation of bone was reduced. As predicted by FEA, histology showed microcrack formation, but then after minimal resorption, remodelling of bone below the biconcave washer. Stable osteosynthesis could be demonstrated by bony union already after 12 weeks, and, while bone remodelling continued in the healed osteotomy, it had decreased around the screws after 19 months. It can be concluded from the biomechanical principles and the histomorphological findings that the AS appears superior to the CLS.
在颌面外科手术中，特别是在骨固定和骨移植固定方面，已经引入了一种带有双凹垫圈的拉力螺钉，即所谓的“锚定螺钉”（AS）。利用二维有限元分析（FEA），分析了该锚定螺钉在其下方骨中产生的米塞斯应力和周向应力，并与传统拉力螺钉下的应力进行了比较。在两名肿瘤患者中，分别在肿瘤手术后12周和19个月取出样本，将锚定螺钉双凹垫圈下方的应力分布与锚定螺钉骨固定术后的组织形态学骨反应相关联。根据皮质骨的厚度，双凹垫圈下方的米塞斯应力集中低于传统拉力螺钉（CLS）头部下方，但在垫圈边缘周围应力最大值更高。锚定螺钉周围的周向应力仅为传统拉力螺钉的一半，因此骨的变形减少。正如有限元分析所预测的，组织学显示有微裂纹形成，但随后经过最小程度的吸收后，双凹垫圈下方的骨发生了重塑。12周后即可通过骨愈合证明稳定的骨固定，并且，虽然在愈合的截骨处骨重塑仍在继续，但19个月后螺钉周围的骨重塑已经减少。从生物力学原理和组织形态学研究结果可以得出结论，锚定螺钉似乎优于传统拉力螺钉。
