Wu Wenjie, Liu Hao, Lou Jigang, Yang Yunbei, Rong Xin, Xu Jianzhong
Department of Orthopedics, West China Hospital, Sichuan University, Chengdu Sichuan, 610041, P.R.China;Department of Orthopedics, Southwest Hospital, Third Military Medical University, Chongqing, 400038, P.R.China.
Department of Orthopedics, West China Hospital, Sichuan University, Chengdu Sichuan, 610041,
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2017 Apr 15;31(4):443-450. doi: 10.7507/1002-1892.201610121.
To analyze the distribution of stress in the upper and lower plates of the prosthesis-bone interface, and the effect of interface pressure on osseointegration.
CT scanning was performed on goats at 1 week after artificial cervical disc replacement to establish the finite element model of C . The stress distribution of the upper and lower plates of the interface was observed. At 6 and 12 months after replacement, Micro-CT scan and three dimensional reconstruction were performed to measure the bone volume fraction (BVF), trabecular number (Tb. N), trabecular thickness (Tb. Th), trabecular separation (Tb. Sp), bone mineral density (BMD), bone surface/bone volume (BS/BV), and trabecular pattern factor (Tb. Pf). The C lower plate and C upper plate of 4 normal goat were chosen to made the cylinder of the diameter of 2 mm. The gene expressions of receptor activator for nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), transforming growth factor β (TGF-β), and macrophage colony-stimulating factor (M-CSF) were detected by real time fluorescent quantitative PCR at immediate after cutting and at 24 and 48 hours after culture. The samples of appropriate culture time were selected to made mechanical loading, and the gene expressions of RANKL, OPG, M-CSF, and TGF-β were detected by real time fluorescent quantitative PCR; no mechanical loading samples were used as normal controls.
Under 25 N axial loading, the stress of the upper plate of C was concentrated to post median region, and the stress of the lower plate to middle-front region and two orbits. According to stress, the plate was divided into 5 regions. The Micro-CT scan showed that BMD, Tb.Th, BVF, and Tb.N significantly increased, and BS/BV, Tb.Sp, and Tb.Pf significantly decreased at 12 months after replacement when compared with ones at 6 months ( <0.05). At 24 and 48 hours after culture, the gene expressions of RANKL, OPG, and TGF-β were signifi-cantly higher than those at immediate ( <0.05), but no significant difference was found between at 24 and 48 hours after culture ( >0.05). The mechanical loading test results at 24 hours after culture showed that the RANKL and OPG gene expressions and OPG/RANKL ratio in C lower plate and C upper plate were significantly up-regulated when compared with controls ( <0.05), but no significant difference was shown in TGF-β and M-CSF gene expressions ( >0.05).
Domestic artificial cervical disc endplate has different pressure distribution, the stress of lower plate is higher than that of upper plate. Pressure has important effect on local osseointegration; the higher pressure area is, the osseointegration is better. Under the maximum pressure in interface, the osteoblast proliferation will increase, which is advantageous to the local osseointegration.
分析人工椎间盘假体-骨界面上下板的应力分布情况以及界面压力对骨整合的影响。
在山羊人工颈椎间盘置换术后1周进行CT扫描，建立C的有限元模型，观察界面上下板的应力分布。置换术后6个月和12个月，进行Micro-CT扫描及三维重建，测量骨体积分数（BVF）、骨小梁数量（Tb.N）、骨小梁厚度（Tb.Th）、骨小梁间距（Tb.Sp）、骨密度（BMD）、骨表面积/骨体积（BS/BV）和骨小梁模式因子（Tb.Pf）。选取4只正常山羊的C下板和C上板制作直径为2 mm的圆柱体，在切割后即刻、培养24小时和48小时通过实时荧光定量PCR检测核因子κB受体活化因子配体（RANKL）、骨保护素（OPG）、转化生长因子β（TGF-β）和巨噬细胞集落刺激因子（M-CSF）的基因表达。选取适当培养时间的样本进行机械加载，通过实时荧光定量PCR检测RANKL、OPG、M-CSF和TGF-β的基因表达；未进行机械加载的样本作为正常对照。
在25 N轴向载荷下，C上板的应力集中于后正中区域，下板的应力集中于中前部区域和两个轨道。根据应力情况，将板分为5个区域。Micro-CT扫描显示，与6个月时相比，置换术后12个月BMD、Tb.Th、BVF和Tb.N显著增加，BS/BV、Tb.Sp和Tb.Pf显著降低（P<0.05）。培养24小时和48小时时，RANKL、OPG和TGF-β的基因表达显著高于切割后即刻（P<0.05），但培养24小时和48小时之间无显著差异（P>0.05）。培养24小时的机械加载试验结果显示，与对照组相比，C下板和C上板的RANKL和OPG基因表达及OPG/RANKL比值显著上调（P<0.05），但TGF-β和M-CSF基因表达无显著差异（P>0.05）。
国产人工颈椎间盘终板压力分布不同，下板应力高于上板。压力对局部骨整合有重要影响；压力越高的区域，骨整合越好。在界面最大压力下，成骨细胞增殖增加，有利于局部骨整合。
