Implant Research Center, School of Biomedical Engineering, Science, and Heath Systems, Drexel University, 3401 Market Street, Suite 300, Philadelphia, PA 19104, USA.
Clin Orthop Relat Res. 2012 Sep;470(9):2599-604. doi: 10.1007/s11999-012-2332-5. Epub 2012 Apr 4.
Implantation of an antibiotic bone cement spacer is used to treat infection of a TKA. Dynamic spacers fashioned with cement-on-cement articulating surfaces potentially facilitate patient mobility and reduce bone loss as compared with their static counterparts, while consisting of a biomaterial not traditionally used for load-bearing articulations. However, their direct impact on patient mobility and wear damage while implanted remains poorly understood.
QUESTIONS/PURPOSES: We characterized patient activity, surface damage, and porous structure of dynamic cement-on-cement spacers.
We collected 22 dynamic and 14 static knee antibiotic cement spacers at revision surgeries at times ranging from 0.5 to 13 months from implantation. For these patients, we obtained demographic data and UCLA activity levels. We characterized surface damage using the Hood damage scoring method and used micro-CT analysis to observe the internal structure, cracking, and porosity of the cement.
The average UCLA score was higher for patients with dynamic spacers than for patients with static spacers, with no differences in BMI or age. Burnishing was the only prevalent damage mode on all the bearing surfaces. Micro-CT analysis revealed the internal structure of the spacers was porous and highly inhomogeneous, including heterogeneous dispersion of radiopaque material and cavity defects. The average porosity was 8% (range, 1%-29%) and more than ½ of the spacers had pores greater than 1 mm in diameter.
Our observations suggest dynamic, cement-on-cement spacers allow for increased patient activity without catastrophic failure. Despite the antibiotic loading and internal structural inhomogeneity, burnishing was the only prevalent damage mode that could be consistently classified with no evidence of fracture or delamination. The porous structure of the spacers varied highly across the surfaces without influencing the material failure.
在全膝关节置换术（TKA）感染的治疗中，植入抗生素骨水泥间隔物是一种常用的方法。与传统的静态间隔物相比，由水泥-水泥关节面构成的动态间隔物具有促进患者活动度和减少骨质丢失的潜力，同时还使用了一种传统上不用于承重关节的生物材料。然而，其在植入过程中对患者活动度和磨损损伤的直接影响仍知之甚少。
问题/目的：我们对动态水泥-水泥间隔物的患者活动度、表面损伤和多孔结构进行了研究。
我们在翻修手术中收集了 22 个动态和 14 个静态膝关节抗生素水泥间隔物，植入时间从 0.5 到 13 个月不等。对于这些患者，我们获得了人口统计学数据和 UCLA 活动水平。我们使用 Hood 损伤评分法对表面损伤进行了评估，并使用微 CT 分析观察了水泥的内部结构、裂纹和孔隙。
与静态间隔物相比，动态间隔物的患者 UCLA 评分更高，而 BMI 或年龄无差异。在所有的承载面上，抛光是唯一常见的损伤模式。微 CT 分析显示，间隔物的内部结构是多孔且高度不均匀的，包括不透射线材料的不均匀分散和腔隙缺陷。平均孔隙率为 8%（范围，1%-29%），超过一半的间隔物具有直径大于 1 毫米的孔隙。
我们的观察结果表明，动态水泥-水泥间隔物可允许患者活动度增加而不会发生灾难性失效。尽管有抗生素负荷和内部结构的不均匀性，但抛光是唯一常见的损伤模式，可以进行一致的分类，没有发现断裂或分层的证据。间隔物的多孔结构在表面上高度变化，但不影响材料失效。
