Institute for Orthopaedic Research and Biomechanics, Trauma Research Center Ulm, University of Ulm, Helmholtzstrasse 14, D-89081 Ulm, Germany.
Department for Functional Materials in Medicine and Dentistry, University of Würzburg, Pleicherwall 2, D-97070 Würzburg, Germany.
Acta Biomater. 2018 Mar 15;69:352-361. doi: 10.1016/j.actbio.2018.01.035. Epub 2018 Feb 2.
Magnesium phosphate minerals have captured increasing attention during the past years as suitable alternatives for calcium phosphate bone replacement materials. Here, we investigated the degradation and bone regeneration capacity of experimental struvite (MgNHPO·6HO) forming magnesium phosphate cements in two different orthotopic ovine implantation models. Cements formed at powder to liquid ratios (PLR) of 2.0 and 3.0 g ml were implanted into trabecular bone using a non-load-bearing femoral drill-hole model and a load-bearing tibial defect model. After 4, 7 and 10 months the implants were retrieved and cement degradation and new bone formation was analyzed by micro-computed tomography (µCT) and histomorphometry. The results showed cement degradation in concert with new bone formation at both defect locations. Both cements were almost completely degraded after 10 months. The struvite cement formed with a PLR of 2.0 g ml exhibited a slightly accelerated degradation kinetics compared to the cement with a PLR of 3.0 g ml. Tartrat-resistant acid phosphatase (TRAP) staining indicated osteoclastic resorption at the cement surface. Energy dispersive X-ray analysis (EDX) revealed that small residual cement particles were mostly accumulated in the bone marrow in between newly formed bone trabeculae. Mechanical loading did not significantly increase bone formation associated with cement degradation. Concluding, struvite-forming cements might be promising bone replacement materials due to their good degradation which is coupled with new bone formation.
Recently, the interest in magnesium phosphate cements (MPC) for bone substitution increased, as they exhibit high initial strength, comparably elevated degradation potential and the release of valuable magnesium ions. However, only few in vivo studies, mostly including non-load-bearing defects in small animals, have been performed to analyze the degradation and regeneration capability of MPC derived compounds. The present study examined the in vivo behavior of magnesiumammoniumphosphate hexahydrate (struvite) implants with different porosity in both mechanically loaded and non-loaded defects of merino sheep. For the first time, the effect of mechanical stimuli on the biological outcome of this clinically relevant replacement material is shown and directly compared to the conventional unloaded defect situation in a large animal model.
在过去的几年中，作为钙磷酸盐骨替代材料的合适替代品，磷酸镁矿物引起了越来越多的关注。在这里，我们研究了在两种不同的绵羊原位植入模型中，实验性鸟粪石（MgNHPO·6HO）形成的磷酸镁水泥的降解和骨再生能力。将粉末与液体的比例（PLR）为 2.0 和 3.0 g/ml 的水泥分别植入非承重股骨钻孔模型和承重胫骨缺损模型的小梁骨中。4、7 和 10 个月后，取出植入物，通过微计算机断层扫描（µCT）和组织形态计量学分析水泥降解和新骨形成。结果表明，在两个缺损部位，水泥降解与新骨形成一致。10 个月后，两种水泥几乎完全降解。PLR 为 2.0 g/ml 的鸟粪石水泥的降解动力学略快于 PLR 为 3.0 g/ml 的水泥。抗酒石酸酸性磷酸酶（TRAP）染色表明在水泥表面有破骨细胞吸收。能谱分析（EDX）表明，小的残余水泥颗粒主要积聚在新形成的骨小梁之间的骨髓中。机械加载并没有显著增加与水泥降解相关的骨形成。结论，鸟粪石形成的水泥可能是有前途的骨替代材料，因为它们具有良好的降解能力，同时伴随着新骨形成。
最近，人们对用于骨替代的磷酸镁水泥（MPC）的兴趣增加了，因为它们具有较高的初始强度、相比较高的降解潜力和释放有价值的镁离子。然而，只有少数体内研究，主要包括小动物的非承重缺陷，已经进行了分析 MPC 衍生化合物的降解和再生能力。本研究检查了不同孔隙率的六水合磷酸镁铵（鸟粪石）植入物在绵羊机械加载和非加载缺陷中的体内行为。首次展示了机械刺激对这种临床相关替代材料生物结果的影响，并直接与大动物模型中常规非加载缺陷情况进行了比较。
