Clinic for Orthopedics, Center for Orthopedics, Trauma Surgery and Spinal Cord Injury, Heidelberg University Hospital, Schlierbacher Landstrasse 200a, 69118, Heidelberg, Germany.
Laboratory of Biomechanics and Implant Research, Center for Orthopedics, Trauma Surgery and Spinal Cord Injury, Heidelberg University Hospital, Schlierbacher Landstrasse 200a, 69118, Heidelberg, Germany.
BMC Musculoskelet Disord. 2022 Oct 29;23(1):945. doi: 10.1186/s12891-022-05895-5.
Antibiotic-loaded polymethylmethacrylate (PMMA) bone cement spacers provide high local antibiotic concentrations and patient mobility during the interim period of two-stage revision for periprosthetic joint infection (PJI). This study compares mechanical characteristics of six dual antibiotic-loaded bone cement (dALBC) preparations made from three different PMMA bone cements. The study`s main objective was to determine the effect of time and antibiotic concentration on mechanical strength of dALBCs frequently used for spacer fabrication in the setting of two-stage revision for PJI.
A total of 84 dual antibiotic-loaded bone cement specimens made of either Copal spacem, Copal G + V or Palacos R + G were fabricated. Each specimen contained 0.5 g of gentamicin and either 2 g (low concentration) or 4 g (high concentration) of vancomycin powder per 40 g bone cement. The bending strength was determined at two different timepoints, 24 h and six weeks after spacer fabrication, using the four-point bending test.
Preparations made from Copal G + V showed the highest bending strength after incubation for 24 h with a mean of 57.6 ± 1.2 MPa (low concentration) and 50.4 ± 4.4 MPa (high concentration). After incubation for six weeks the bending strength had decreased in all six preparations and Palacos R + G showed the highest bending strength in the high concentration group (39.4 ± 1.6 MPa). All low concentration preparations showed superior mechanical strength compared to their high concentration (4 g of vancomycin) counterpart. This difference was statistically significant for Copal spacem and Copal G + V (both p < 0.001), but not for Palacos R + G (p = 0.09).
This study suggests that mechanical strength of antibiotic-loaded PMMA bone cement critically decreases even over the short time period of six weeks, which is the recommended interim period in the setting of two-stage revision. This potentially results in an increased risk for PMMA spacer fracture at the end of the interim period and especially in patients with prolonged interim periods. Finally, we conclude that intraoperative addition of 4 g of vancomycin powder per 40 g of gentamicin-premixed Palacos R + G (Group D) is mechanically the preparation of choice if a dual antibiotic-loaded bone cement spacer with high antibiotic concentrations and good stability is warranted. In any case the written and signed informed consent including the off-label use of custom-made antibiotic-loaded PMMA bone cement spacers must be obtained before surgery.
在二期翻修治疗人工关节周围感染（PJI）中，载抗生素聚甲基丙烯酸甲酯（PMMA）骨水泥 spacer 可提供高局部抗生素浓度并保证患者的活动度。本研究比较了三种不同 PMMA 骨水泥制成的六种双抗生素载骨水泥（dALBC）的力学特性。该研究的主要目的是确定在二期翻修 PJI 治疗中，频繁用于 spacer 制作的 dALBC 制剂的抗生素浓度和时间对机械强度的影响。
共制备 84 个 Copal spacem、Copal G+V 或 Palacos R+G 双抗生素载骨水泥试件。每个试件含 40g 骨水泥中含 0.5g 庆大霉素和 2g（低浓度）或 4g（高浓度）万古霉素粉末。在 spacer 制备后 24 小时和 6 周时，使用四点弯曲试验分别在两个不同时间点确定弯曲强度。
孵育 24 小时后，Copal G+V 制备物的弯曲强度最高，低浓度组平均为 57.6±1.2MPa，高浓度组为 50.4±4.4MPa。孵育 6 周后，所有 6 种制剂的弯曲强度均下降，高浓度组 Palacos R+G 的弯曲强度最高（39.4±1.6MPa）。所有低浓度制剂的机械强度均优于高浓度（4g 万古霉素）制剂，Copal spacem 和 Copal G+V 差异有统计学意义（均 p<0.001），但 Palacos R+G 差异无统计学意义（p=0.09）。
本研究表明，即使在 6 周的短时间内，抗生素负载 PMMA 骨水泥的机械强度也会显著下降，这是二期翻修中推荐的间隔时间。这可能会导致在间隔期末期 PMMA spacer 骨折的风险增加，尤其是在间隔期延长的患者中。最后，我们得出结论，如果需要高抗生素浓度和良好稳定性的双抗生素载骨水泥 spacer，术中每 40g 庆大霉素混合的 Palacos R+G 中添加 4g 万古霉素粉末（D 组）是机械上的首选制剂。在任何情况下，都必须在手术前获得书面和签署的知情同意书，包括定制抗生素负载 PMMA 骨水泥 spacer 的标签外使用。
