Al-Sukhun Jehad, Penttilä Heikki, Ashammakhi Nureddin
Department of Oral & Maxillofacial Surgery, Euro-Oral Hammaslääkärikeskus, Helsinki, Finland.
J Craniofac Surg. 2011 Jul;22(4):1294-8. doi: 10.1097/SCS.0b013e31821c6afd.
The purpose of this study was to develop a finite element model (FEM) of a human orbit, who experienced a pure orbital blowout fracture, to study the effect of the geometrical mismatch-induced stresses on the orbital floor/graft interface and how to improve the graft design when restoring the orbital floor.
A FEM of the orbit and the globe of 1 patient who experienced pure orbital blowout fracture and treated with autogenous bone graft was generated based on computed tomographic scans. Simulations were performed with a computer using a commercially available finite element software NISA (EMRC, Troy, MI). The FEM was then used to study the effects of changing the geometry, position, material properties, and method of fixation of the autogenous bone graft on its predictions.
The factors that had the biggest impact on the predicted principal strain magnitudes were absence of cancellous bone (up to 60%) and bony support of the graft (up to 50%). Applying rigid fixation reduced stresses by 30% posteriorly and by almost 100% anteriorly. Alterations to the geometry of the bone graft, such as an increase in its thickness, increased principal strain magnitudes (up to 42%).
Applying rigid fixation reduced principal stresses significantly. The role of rigid fixation becomes more prominent when there is no bony support posteriorly and/or medially. This study also highlights the importance of preserving cancellous bone, when harvesting and preparing the autogenous bone graft to reconstruct the orbital floor. The possibility that absence of cancellous bone and the resulting stresses may be a source of graft resorption and/or failure cannot be excluded.
本研究的目的是建立一个经历单纯眼眶爆裂性骨折的人体眼眶有限元模型（FEM），以研究几何形状不匹配引起的应力对眶底/移植物界面的影响，以及在修复眶底时如何改进移植物设计。
基于计算机断层扫描生成了1例经历单纯眼眶爆裂性骨折并接受自体骨移植治疗的患者的眼眶和眼球有限元模型。使用商用有限元软件NISA（EMRC，特洛伊，密歇根州）在计算机上进行模拟。然后使用有限元模型研究改变自体骨移植物的几何形状、位置、材料特性和固定方法对其预测结果的影响。
对预测主应变大小影响最大的因素是松质骨缺失（高达60%）和移植物的骨支撑（高达50%）。采用刚性固定可使后部应力降低30%，前部应力降低近100%。骨移植物几何形状的改变，如厚度增加，会使主应变大小增加（高达42%）。
采用刚性固定可显著降低主应力。当后部和/或内侧没有骨支撑时，刚性固定的作用更为突出。本研究还强调了在采集和制备自体骨移植物以重建眶底时保留松质骨的重要性。不能排除松质骨缺失及由此产生的应力可能是移植物吸收和/或失败的原因。
