BACKGROUND Several studies using positron emission tomography (PET) show highly elevated periprosthetic bone uptake of fluorine-18 sodium fluoride (18F-fluoride), suggestive of implant loosening after arthroplasty. Focus so far has been on qualitative but not on quantitative assessment. There is also a lack of intraoperative confirmation of preoperative 18F-fluoride PET findings. Although the method seems to have acceptable accuracy and high sensitivity, an attempt to improve the specificity and an overall validation of the method appear warranted. QUESTIONS/PURPOSES (1) Is there a difference in 18F-fluoride uptake around loose versus well-fixed THA and TKA components? (2) Can 18F-fluoride uptake measures provide a threshold that differentiates loose from well-fixed implants undergoing revision for a variety of septic and aseptic indications? (3) In a population restricted to THA and TKA undergoing revision for aseptic indications, can measurement of 18F-fluoride uptake still distinguish loose from well-fixed components? (4) What is the interrater reliability of measuring 18F-fluoride uptake? METHODS This was a retrospective assessment of a diagnostic test, 18F-fluoride PET/CT, which was performed prior to revision surgery. We included 63 patients with 31 THAs and 32 TKAs. Sixty-five percent of patients were female, and the mean age at 18F-fluoride PET/CT was 66 years. The THA had different modes of fixation (cemented, cementless, and hybrid; 45%, 32%, and 23%, respectively), whereas all TKAs were cemented. Imaging was conducted using routine protocols 1 hour after tracer injection. The interobserver reproducibility was analyzed using Spearman rank correlations and Bland-Altman analyses. Two independent observers were trained separately by a nuclear physician to measure maximal periprosthetic standardized uptake values (SUVmax) for each arthroplasty component (n = 126). Findings at surgery (whether the components were well fixed or loose, as well as the presence or absence of infection) were used as a reference. Presence of periprosthetic joint infection was retrospectively determined based on the criteria suggested by the European Bone and Joint Infection Society (EBJIS): clinical features in combination with blood analysis, synovial fluid cytologic analysis, and microbiology test results. Receiver operating characteristic (ROC) curves were plotted to assess the area under the curve (AUC) for each investigated component separately, indicating suitable SUVmax thresholds that differentiate loose from well-fixed components. After excluding patients with confirmed or suspected PJI per the EBJIS criteria (n = 12), the above analysis was repeated for the remaining patients with aseptic loosening (n = 51). RESULTS We found higher 18F-fluoride uptake around loose versus well-fixed components in all but femoral TKA components (median [range] SUVmax for well-fixed versus loose THA cups 10 [7 to 30] versus 22 [6 to 64], difference of medians 12; p = 0.003; well-fixed versus loose TKA femoral components 14 [4 to 41] versus 19 [9 to 42], difference of medians 5; p = 0.38). We identified favorable ROC curves for all investigated components except femoral TKA components (THA cups AUC 0.81 [best threshold 13.9]; THA femoral stems AUC 0.9 [best threshold 17.3]; femoral TKA components AUC 0.6 [best threshold 14.3]; tibial TKA components AUC 0.83 [best threshold 15.8]). 18F-fluoride was even more accurate at diagnosing loosening when we limited the population to those patients believed not to have prosthetic joint infection (THA cups AUC 0.87 [best threshold 14.2]; THA femoral stems AUC 0.93 [best threshold 15.0]; femoral TKA components AUC 0.65 [best threshold 15.8]; tibial TKA components AUC 0.86 [best threshold 14.7]). We found strong interrater correlation when assessing SUVmax values, with Spearman ρ values ranging from 0.96 to 0.99 and Bland-Altman plots indicating excellent agreement between the two independent observers. CONCLUSION Measuring SUVmax after 18F-fluoride PET/CT is a useful adjunct in the diagnostic evaluation for suspected implant loosening after THA and TKA. The method appears to be both accurate and reliable in diagnosing implant loosening for all components except femoral TKA components. In a real-world mixed population with both low-grade infection and aseptic loosening, the method seems to be fairly easy to learn and helpful to subspecialized arthroplasty clinicians. When infection can be ruled out, the method probably performs even better. Further prospective studies are warranted to explore the reason why femoral TKA component loosening was more difficult to ascertain using this novel technique. LEVEL OF EVIDENCE Level III, diagnostic study.

中文翻译：

---

18F-氟化物 PET/CT 是诊断全关节置换术后松动的准确工具吗？


背景技术使用正电子发射断层扫描（PET）的几项研究显示，假体周围骨对氟-18氟化钠（18F-氟化物）的吸收高度升高，提示关节置换术后植入物松动。到目前为止，重点是定性评估，而不是定量评估。术前 18F-氟化物 PET 结果也缺乏术中确认。尽管该方法似乎具有可接受的准确性和高灵敏度，但仍需要尝试提高该方法的特异性和整体验证。问题/目的 (1) 松散的 THA 和 TKA 组件与固定良好的组件周围的 18F-氟化物吸收是否存在差异？ (2) 18F-氟化物吸收测量能否提供一个阈值来区分松动和固定良好的种植体，并针对各种脓毒症和无菌适应症进行翻修？ (3) 在仅限接受 THA 和 TKA 且因无菌适应症而进行翻修的人群中，18F-氟化物吸收测量仍然可以区分松动部件和固定部件吗？ (4) 测量 18F-氟化物吸收的人间可靠性是多少？方法 这是对修复手术前进行的 18F-氟化物 PET/CT 诊断测试的回顾性评估。我们纳入了 63 名接受 31 个 THA 和 32 个 TKA 的患者。 65% 的患者为女性，18F-氟化物 PET/CT 的平均年龄为 66 岁。 THA 有不同的固定模式（骨水泥固定、非骨水泥固定和混合固定；分别为 45%、32% 和 23%），而所有 TKA 均采用骨水泥固定。示踪剂注射后 1 小时使用常规方案进行成像。使用 Spearman 等级相关性和 Bland-Altman 分析来分析观察者间的再现性。 两名独立观察员分别接受核医师的培训，以测量每个关节置换术组件的最大假体周围标准化摄取值 (SUVmax) (n = 126)。以手术时的结果（部件是否固定良好或松动，以及是否存在感染）作为参考。根据欧洲骨与关节感染协会（EBJIS）建议的标准回顾性确定假体周围关节感染的存在：临床特征结合血液分析、滑液细胞学分析和微生物学检测结果。绘制受试者工作特征 (ROC) 曲线，以分别评估每个研究组件的曲线下面积 (AUC)，表明区分松散组件和固定良好组件的合适 SUVmax 阈值。根据 EBJIS 标准排除确诊或疑似 PJI 的患者 (n = 12) 后，对其余无菌性松动患者 (n = 51) 重复上述分析。结果 我们发现，除股骨 TKA 部件外，所有松散部件周围的 18F 氟化物吸收量均高于固定良好部件（固定良好 THA 杯与松散 THA 杯的中位 [范围] SUVmax 10 [7 至 30] 与 22 [6 至 64]，差异中位数 12；p = 0.003；固定良好的 TKA 股骨组件 14 [4 至 41] 与 19 [9 至 42]，中位数差值 5；我们确定了除股骨 TKA 组件外的所有研究组件的良好 ROC 曲线（THA 杯 AUC 0.81 [最佳阈值 13.9]；THA 股骨柄 AUC 0.9 [最佳阈值 17.3]；股骨 TKA 组件 AUC 0.6 [最佳阈值 14.3]；胫骨 TKA 组件 AUC 0.83 [最佳阈值 15.8]）。 当我们将人群限制为那些被认为没有假体关节感染的患者时，18F-氟化物在诊断松动方面甚至更加准确（THA 杯 AUC 0.87 [最佳阈值 14.2]；THA 股骨柄 AUC 0.93 [最佳阈值 15.0]；股骨 TKA 组件AUC 0.65 [最佳阈值 15.8]；胫骨 TKA 成分 AUC 0.86 [最佳阈值 14.7]）。我们在评估 SUVmax 值时发现了很强的参与者间相关性，Spearman ρ 值范围为 0.96 至 0.99，Bland-Altman 图表明两个独立观察者之间具有极好的一致性。结论 18F-氟化物 PET/CT 后测量 SUVmax 对于 THA 和 TKA 后疑似种植体松动的诊断评估是有用的辅助手段。该方法对于诊断除股骨 TKA 部件之外的所有部件的植入物松动似乎既准确又可靠。在现实世界中存在低度感染和无菌性松动的混合人群中，该方法似乎相当容易学习，并且对专业关节置换术临床医生有帮助。当可以排除感染时，该方法的效果可能会更好。需要进一步的前瞻性研究来探讨使用这种新技术更难以确定股骨 TKA 假体松动的原因。证据级别 III 级，诊断研究。