Department of Materials Science and Engineering, Uppsala University, Uppsala, Sweden.
Department of Neurosurgery, Clinical Neurosciences, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
Acta Biomater. 2021 Jul 1;128:502-513. doi: 10.1016/j.actbio.2021.04.015. Epub 2021 Apr 20.
The use of calcium phosphates (CaPs) as synthetic bone substitutes should ideally result in a volumetric balance with concomitant bone formation and degradation. Clinical data on such properties is nevertheless lacking, especially for monetite-based CaPs. However, a monetite-based composite implant has recently shown promising cranial reconstructions, with both CaP degradation and bone formation. In this study, the volumetric change at the implant site was quantified longitudinally by clinical computed tomography (CT). The retrospective CT datasets had been acquired postoperatively (n = 10), in 1-year (n = 9) and 3-year (n = 5) follow-ups. In the 1-year follow-up, the total volumetric change at the implant site was -8 ± 8%. A volumetric increase (bone formation) was found in the implant-bone interface, and a volumetric decrease was observed in the central region (CaP degradation). In the subjects with 2- or 3-year follow-ups, the rate of volumetric decrease slowed down or plateaued. The reported degradation rate is lower than previous clinical studies on monetite, likely due to the presence of pyrophosphate in the monetite-based CaP-formulation. A 31-months retrieval specimen analysis demonstrated that parts of the CaP had been remodeled into bone. The CaP phase composition remained stable, with 6% transformation into hydroxyapatite. In conclusion, this study demonstrates successful bone-bonding between the CaP-material and the recipient bone, as well as a long-term volumetric balance in cranial defects repaired with the monetite-based composite implant, which motivates further clinical use. The developed methods could be used in future studies for correlating spatiotemporal information regarding bone regeneration and CaP degradation to e.g. patient demographics. STATEMENT OF SIGNIFICANCE: In bone defect reconstructions, the use of calcium phosphate (CaP) bioceramics ideally results in a volumetric balance between bone formation and CaP degradation. Clinical data on the volumetric balance is nevertheless lacking, especially for monetite-based CaPs. Here, this concept is investigated for a composite cranial implant. The implant volumes were quantified from clinical CT-data: postoperatively, one year and three years postoperatively. In total, -8 ± 8% (n = 9) volumetric change was observed after one year. But the change plateaued, with only 2% additional decrease at the 3-year follow-up (n = 5), indicating a lower CaP degradation rate. Osseointegration was seen at the bone-implant interface, with a 9 ± 7% volumetric change after one year. This study presented the first quantitative spatiotemporal CT analysis of monetite-based CaPs.
使用磷酸钙（CaP）作为合成骨替代物，理想情况下应实现体积平衡，同时伴有骨形成和降解。然而，临床上缺乏此类特性的相关数据，尤其是对于基于磷灰石的 CaP。然而，最近一种基于磷灰石的复合材料植入物已显示出对颅骨重建的良好效果，同时伴有 CaP 降解和骨形成。在这项研究中，通过临床计算机断层扫描（CT）对植入物部位的体积变化进行了纵向定量。回顾性 CT 数据集是在术后（n=10）、1 年（n=9）和 3 年（n=5）随访时获得的。在 1 年的随访中，植入物部位的总体积变化为-8±8%。在植入物-骨界面发现了体积增加（骨形成），而在中央区域观察到了体积减少（CaP 降解）。在随访时间为 2 年或 3 年的受试者中，体积减少的速度减慢或趋于平稳。报道的降解速度低于之前对磷灰石的临床研究，这可能是由于在基于磷灰石的 CaP 配方中存在焦磷酸盐。31 个月的回收样本分析表明，部分 CaP 已重塑为骨。CaP 相组成保持稳定，有 6%转化为羟基磷灰石。总之，这项研究表明，CaP 材料与受体骨之间实现了骨结合，并且使用基于磷灰石的复合材料植入物修复的颅骨缺损具有长期的体积平衡，这激发了进一步的临床应用。所开发的方法可用于未来的研究，将骨再生和 CaP 降解的时空信息与例如患者的人口统计学信息相关联。意义声明：在骨缺损重建中，使用磷酸钙（CaP）生物陶瓷理想情况下会导致骨形成和 CaP 降解之间的体积平衡。然而，临床上缺乏关于体积平衡的相关数据，尤其是对于基于磷灰石的 CaP。在此，我们对一种基于复合材料的颅植入物进行了研究。通过临床 CT 数据对植入物体积进行了定量：术后、术后 1 年和 3 年。总体而言，术后 1 年观察到-8±8%（n=9）的体积变化。但变化趋于平稳，在 3 年随访时仅增加了 2%（n=5），这表明 CaP 降解速度较低。在骨-植入物界面观察到了骨整合，术后 1 年体积变化为 9±7%。本研究首次对基于磷灰石的 CaP 进行了定量时空 CT 分析。
