Effect of Hydroxyapatite porous characteristics on healing outcomes in rabbit posterolateral spinal fusion model
Effect of Hydroxyapatite porous characteristics on healing outcomes in rabbit posterolateral spinal fusion model
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DOI：
10.1007/s00586-007-0501-0
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发表时间：
2007-12-01
影响因子：
2.8
通讯作者：
Minami, Akio
中科院分区：
文献类型：
--
作者：
Motomiya, Makoto;Ito, Manabu;Minami, Akio
羟基磷灰石（hydroxyapatite，HA）作为骨移植替代材料已广泛应用于临床。为了提高HA的愈合能力，已经进行了许多研究以揭示其最佳结构特征以获得更好的愈合结果。在脊柱重建手术中，非互连多孔HA已被用作骨移植物延长器，以避免自体骨采集。然而，关于HA结构特征在后外侧腰椎横突间融合（PLF）中的作用的实验研究很少。本研究的目的是研究HA多孔特性对兔PLF模型愈合结果的影响，以阐明HA作为骨移植物扩展器的适当结构特征。36只成年雌性日本白色家兔在L5-6节段接受双侧横突间融合术，未进行内固定。我们制备了三种不同孔隙率的HA：15%孔隙率的HA（HA 15%），50%孔隙率的HA（HA 50%）和85%孔隙率的HA（HA 85%），所有这些都是临床可用的材料。HA15%和HA50%具有很少的互连孔，而新近开发的HA85%具有丰富的互连孔。根据移植材料的不同，随机分为4组：HA 15%+自体骨组、HA 50%+自体骨组、HA 85%+自体骨组、单纯自体骨组。在手术后5周对动物实施安乐死，并进行尸检分析，包括生物力学测试、放射照相和组织学评价。三个HA组之间的融合率和/或弯曲刚度没有统计学显著差异。然而，在组织学和放射学分析中，HA 85%组的骨长入率和直接骨结合率均显著高于HA 15%和HA 50%组，尽管三个HA组之间融合块的骨体积率值相似。在HA 85%组中，通过互连孔在整个植入HA中实现骨长入，HA颗粒和新矿化骨之间具有良好的结合。而在非连通多孔HA组中，仅在植入HA的周边孔隙处可见少量骨长入，其表面大多被纤维组织或空洞覆盖。当前研究表明，HA多孔特性对兔PLF模型中的组织学结局有影响。我们想得出的结论是，互连的高多孔结构似乎是有前途的PLF的环境中产生融合质量与更高的细胞活力的点。这是因为与非互连多孔HA相比，HA 85%在与融合块中新形成的骨整合方面具有上级优势。然而，HA的多孔改性对融合率和机械强度的影响很小，因为融合节段的初步稳定主要是通过桥接植入材料外相邻横突之间的骨来实现的，而不是PLF中新形成的骨与HA颗粒之间的整合程度。
Hydroxyapatite (HA) has been commonly used as a bone graft substitute in various kinds of clinical fields. To improve the healing capability of HA, many studies have been performed to reveal its optimal structural characteristics for better healing outcomes. In spinal reconstruction surgery, non-interconnected porous HAs have already been applied as a bone graft extender in order to avoid autogenous bone harvesting. However, there have been few experimental studies regarding the effects of the structural characteristics of HA in posterolateral lumbar intertransverse process spine fusion (PLF). The aims of this study were to investigate the effect of HA porous characteristics on healing outcomes in a rabbit PLF model in order to elucidate appropriate structural characteristics of HA as a bone graft extender. Thirty-six adult female Japanese White rabbits underwent bilateral intertransverse process fusion at the level of L5-6 without internal fixation. We prepared three types of HA with different porosities: HA with 15% porosity (HA15%), HA with 50% porosity (HA50%), and HA with 85% porosity (HA85%), all of which were clinically available materials. The HA15% and HA50% had few interconnecting pores, whereas the HA85%, which was a recently developed material, had abundant interconnecting pores. All rabbits were randomly divided into the following four groups according to the grafted materials: (1) HA15% + autogenous bone, (2) HA50% + autogenous bone, (3) HA85% + autogenous bone, (4) pure autogenous bone graft. The animals were euthanized at 5 weeks after surgery, and post-mortem analyses including biomechanical testing, radiographical and histological evaluations were performed. There was no statistically significant difference in either fusion rate and/or bending stiffness among the three HA groups. However, in histological and radiological analyses, both bone ingrowth rate and direct bone bonding rate in the HA85% group were significantly higher than those in the HA15% and HA50% groups, despite the similar value of bone volume rate in fusion mass among the three HA groups. In the HA85% group, bone ingrowth was achieved throughout the implanted HAs via interconnecting pores and there was excellent unification between the HA granules and the newly mineralized bone. On the other hand, in the non-interconnected porous HA groups, only a little bone ingrowth could be seen at the peripheral pores of the implanted HA, and its surface was mostly covered with fibrous tissue or empty space. The current study demonstrated that the HA porous characteristics had an effect on the histological outcomes in a rabbit PLF model. We would like to conclude that the interconnected high porous structure seems to be promising for the environment of PLF in the point of producing fusion mass with higher cellular viability. This is because the HA85% is superior in terms of integration with the newly formed bone in fusion mass compared to the non-interconnected porous HAs. However, the porous modifications of HA have little influence on fusion rate and mechanical strength because primary stabilization of the fusion segment is mainly achieved by bridging bone between the adjacent transverse processes outside the implanted materials, rather than the degree of integration between the newly formed bone and the HA granules in PLF.