Bruna-Rosso Claire, Arnoux Pierre-Jean, Bianco Rohan-Jean, Godio-Raboutet Yves, Fradet Léo, Aubin Carl-Éric
Department of Mechanical Engineering, Polytechnique Montréal, Montreal, Canada; iLab - Spine International Laboratory - Spine Imaging and Biomechanics.
iLab - Spine International Laboratory - Spine Imaging and Biomechanics; Laboratoire de Biomécanique Appliquée, Aix-Marseille Université, Marseille, France.
Int J Spine Surg. 2016 Apr 22;10:16. doi: 10.14444/3016. eCollection 2016.
Sacroiliac joint (SIJ) is a known chronic pain-generator. The last resort of treatment is the arthrodesis. Different implants allow fixation of the joint, but to date there is no tool to analyze their influence on the SIJ biomechanics under physiological loads. The objective was to develop a computational model to biomechanically analyze different parameters of the stable SIJ fixation instrumentation.
A comprehensive finite element model (FEM) of the pelvis was built with detailed SIJ representation. Bone and sacroiliac joint ligament material properties were calibrated against experimentally acquired load-displacement data of the SIJ. Model evaluation was performed with experimental load-displacement measurements of instrumented cadaveric SIJ. Then six fixation scenarios with one or two implants on one side with two different trajectories (proximal, distal) were simulated and assessed with the FEM under vertical compression loads.
The simulated S1 endplate displacement reduction achieved with the fixation devices was within 3% of the experimentally measured data. Under compression loads, the uninstrumented sacrum exhibited mainly a rotation motion (nutation) of 1.38° and 2.80° respectively at 600 N and 1000 N, with a combined relative translation (0.3 mm). The instrumentation with one screw reduced the local displacement within the SIJ by up to 62.5% for the proximal trajectory vs. 15.6% for the distal trajectory. Adding a second implant had no significant additional effect.
A comprehensive finite element model was developed to assess the biomechanics of SIJ fixation. SIJ devices enable to reduce the motion, mainly rotational, between the sacrum and ilium. Positioning the implant farther from the SIJ instantaneous rotation center was an important factor to reduce the intra-articular displacement.
Knowledge provided by this biomechanical study enables improvement of SIJ fixation through optimal implant trajectory.
骶髂关节（SIJ）是一种已知的慢性疼痛产生源。治疗的最后手段是关节融合术。不同的植入物可实现关节固定，但迄今为止，尚无工具可分析它们在生理负荷下对骶髂关节生物力学的影响。目的是开发一种计算模型，以对稳定的骶髂关节固定器械的不同参数进行生物力学分析。
构建了一个包含详细骶髂关节表征的骨盆综合有限元模型（FEM）。根据实验获取的骶髂关节负荷-位移数据校准骨骼和骶髂关节韧带的材料属性。通过对植入仪器的尸体骶髂关节进行实验负荷-位移测量来进行模型评估。然后模拟了六种固定方案，即在一侧使用一个或两个植入物，有两种不同的轨迹（近端、远端），并在垂直压缩负荷下用有限元模型进行评估。
固定装置实现的模拟S1终板位移减少在实验测量数据的3%以内。在压缩负荷下，未植入器械的骶骨在600 N和1000 N时分别主要表现出1.38°和2.80°的旋转运动（前屈），伴有0.3 mm的联合相对平移。对于近端轨迹，使用一枚螺钉的器械将骶髂关节内的局部位移减少了高达62.5%，而对于远端轨迹则为15.6%。添加第二枚植入物没有显著的额外效果。
开发了一个综合有限元模型来评估骶髂关节固定的生物力学。骶髂关节装置能够减少骶骨和髂骨之间的运动，主要是旋转运动。将植入物放置在离骶髂关节瞬时旋转中心更远的位置是减少关节内位移的一个重要因素。
这项生物力学研究提供的知识有助于通过优化植入物轨迹来改进骶髂关节固定。
