Morgan Patrick M, Sharkey Peter, Ghanem Elie, Parvizi Javad, Clohisy John C, Burnett R Stephen J, Barrack Robert L
Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, MO 63110, USA.
J Bone Joint Surg Am. 2009 Sep;91(9):2124-9. doi: 10.2106/JBJS.H.00853.
The accurate preoperative diagnosis of infection is an essential component of decision-making prior to revision total knee arthroplasty. When preoperative modalities used to detect infection reveal equivocal findings, the surgeon may rely on intraoperative testing. While intraoperative Gram stains are routinely performed during revision total knee arthroplasty, their value remains unclear.
We retrospectively reviewed the records on 945 revision total knee arthroplasties performed at three university institutions to which patients were referred for total joint arthroplasty; the results of an intraoperative Gram stain were available for review in 921 cases (97.5%). Of these knees, 247 were classified as infected on the basis of (1) the presence of the same organism in two cultures; (2) growth, on solid media, of an organism as well as other objective evidence of infection; (3) histologic evidence of acute inflammation; (4) gross purulence; and/or (5) an actively draining sinus. We reviewed the results of preoperative laboratory studies, which included measurements of the erythrocyte sedimentation rate, C-reactive protein values, and white blood-cell count in 90%, 76%, and 98% of cases, respectively. Preoperative aspiration to obtain a specimen for culture and a cell count was performed routinely at one center and selectively at the other two centers, and the results were available for review in 439 (48%) of the 921 cases.
Intraoperative Gram staining was found to have a sensitivity of 27% and a specificity of 99.9%. The positive and negative predictive values were 98.5% and 79%, respectively. The test accuracy was 80%. Patients with a true-positive Gram stain had a significantly higher preoperative white blood-cell count, C-reactive protein level, and nucleated cell count in the aspirate when compared with patients with a false-negative Gram stain (p < 0.001). In no case did the results of the intraoperative Gram stain alter treatment.
The intraoperative Gram stain was found to have poor sensitivity and a poor negative predictive value, and its results did not alter the treatment of any patient undergoing revision total knee arthroplasty because of a suspected infection. These data do not support the routine use of intraoperative Gram staining in revision total knee arthroplasty; instead, they suggest a much more limited role for this test.
感染的准确术前诊断是翻修全膝关节置换术决策的重要组成部分。当用于检测感染的术前方法显示出不明确的结果时，外科医生可能会依赖术中检测。虽然术中革兰氏染色在翻修全膝关节置换术中常规进行，但其价值仍不明确。
我们回顾性分析了在三家大学机构进行的945例翻修全膝关节置换术的记录，这些患者因全关节置换术被转诊至这些机构；921例（97.5%）有术中革兰氏染色结果可供审查。在这些膝关节中，247例根据以下标准被分类为感染：（1）两种培养物中存在相同的生物体；（2）在固体培养基上某种生物体生长以及其他感染的客观证据；（3）急性炎症的组织学证据；（4）肉眼可见的脓性分泌物；和/或（5）有活动性引流的窦道。我们回顾了术前实验室检查结果，分别在90%、76%和98%的病例中包括红细胞沉降率、C反应蛋白值和白细胞计数的测量。在一个中心常规进行术前抽吸以获取培养标本和细胞计数，在另外两个中心选择性进行，921例中的439例（48%）有结果可供审查。
术中革兰氏染色的敏感性为27%，特异性为99.9%。阳性和阴性预测值分别为98.5%和79%。检测准确性为80%。与革兰氏染色假阴性的患者相比，革兰氏染色真阳性的患者术前白细胞计数、C反应蛋白水平和抽吸物中有核细胞计数显著更高（p<0.001）。在任何情况下，术中革兰氏染色结果均未改变治疗方案。
术中革兰氏染色敏感性差且阴性预测值低，其结果未改变任何因疑似感染而接受翻修全膝关节置换术患者的治疗。这些数据不支持在翻修全膝关节置换术中常规使用术中革兰氏染色；相反，它们表明该检测的作用更为有限。
