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人工关节置换与关节假体周围感染

已有 3424 次阅读 2015-5-22 02:20 |个人分类:科苑进展|系统分类:科普集锦| 关节置换, 关节假体植入, 假体周围感染

人工全关节置换(total joint arthroplasty)是处理严重退行性关节疾病的最终选项。随着技术的成熟,人工全关节置换现在被看做是外科史上最成功的干预形式之一。可是,人工关节植入所引起的关节假体周围感染(periprostheticjoint infection, PJI)却是骨整形学面临的最严峻的挑战。

仅在美国,每年关节假体周围感染病例就高达33000,据估计,到2020年这一数字可能将上升到70000例。PJI构成了如今膝关节置换失败原因的25%,髋关节置换失败原因的15%,估计2030年,PJI将构成关节置换失败原因的60%。

PJI病例数不断升高的原因是多方面的。首先,开展这一手术的人数在急剧增加,而且在可预见的未来,这一趋势不会改变;其次,选择关节置换者常并发有肥胖,糖尿病和心血管疾病等高感染风险因素;再次,导致关节置换周围感染的微生物对抗生素的抗性在增高,例如,在很多医疗机构中,MRSA构成了超过一半的PJI病例;最后,随着诊断技术和能力的提升,越来越多的感染能通过先进的检测手段确诊。

PJI病因与诊断

PJI发病原因涉及移植体,患者免疫系统和侵犯的微生物三者间复杂的相互作用。研究发现,只需少量的微生物即可引起PJI。微生物粘附在移植假体上形成生物被膜(biofilm),这种菌膜能够帮助致病微生物逃避检测,常规抗微生物药物和宿主免疫系统的攻击。形成生物被膜的微生物在行为上与单个个体或浮游菌不同,其微生物在如抗生素等环境应激情况下依旧能顽强的存活。

正确区分开PJI和其它导致关节假体移植失败的因素十分重要。PJI最常见的症状为疼痛,急性期多在局部呈现红肿热疼等炎症经典症状;而慢性炎症下的症状并不典型,可能只表现为疼痛,并可能主诉在骨移植界面移植假体的松动感。总之,无论是急性还是慢性感染,所呈现的症状都难于和其它类型炎症呈现的症状区分。骨整形外科中用于诊断PJI所用影像学手段包括MRI,PET扫描,骨扫描和铟标记WBC扫描等,但这些方法所获结果常常并不理想,成像手段并不能直接确认PJI;而PJI的实验室检测多都有参考意义,却未能解决诊断特异性的问题,指标包括红细胞沉降率(ESR),血清C反应蛋白(CRP),滑膜液中白细胞数和类型,白细胞酯酶检测试剂(LeukocyteEsterase Test Strip)等。滑膜液细菌培养常常失败,可能与抗生素使用,细菌数量偏低和培养技术有限等有关。

诊断的新手段:α-防御素(alpha-defensin)

滑膜液中PJI的生物标志物包括炎症蛋白,细胞因子,抗菌肽等在宿主免疫反应中具有重要的作用。CDDiagnostics致力于通过关节液分析研发关节疾病的诊断技术,他们在超过50个生物标志物的基础上使用系列的滑膜液生物标志物研究和评价,确定了更准确的用于PJI诊断用生物标志物,结合运用一种叫做α-防御素的抗菌肽和CRP的检测方法Synovasure™。Synovasure试剂检测α-防御素在滑膜液中浓度,其在PJI下急剧升高,对PJI的敏感性和特异性分别高达97%和96%;结合滑膜液中CRP水平,能更好的排斥假阳性情况,给临床医师更高的PJI诊断准确率。

 

相应学术论文:Deirmengian C1, Kardos K,Kilmartin P, Gulati S, Citrano P, Booth RE Jr. The Alpha-defensin Test forPeriprosthetic Joint Infection Responds to a Wide Spectrum of Organisms. ClinOrthop Relat Res. 2015 Jan 29.

摘要:

Abstract

BACKGROUND:

The alpha-defensin test has beenpreviously demonstrated to be highly accurate in the diagnosis of prostheticjoint infection (PJI), nearly matching the Musculoskeletal Infection Societydefinition for PJI. However, the relationship between alpha-defensin levels anddiffering infecting organism has not yet been investigated.

QUESTIONS/PURPOSES:

The purpose of this study is to describethe breadth of organisms that can trigger a positive synovial fluidalpha-defensin test result in the setting of PJI and also to assess themagnitude of the alpha-defensin result in terms of various pathogencharacteristics.

METHODS:

Between December 2012 and March 2014,one laboratory processed 2319 synovial fluid samples for alpha-defensintesting. The present study reviewed the results of the 1937 samples thatsimultaneously had a synovial fluid culture performed; these came from 418surgeons in 42 states. The overall culture-positive rate was 49% (244 of 498)among alpha-defensin-positive synovial fluids and 1% (19 of 1439) amongalpha-defensin-negative synovial fluids. The organisms recovered from 244alpha-defensin-positive, culture-positive fluids were recorded and groupedbased on various characteristics, including Gram type, species, virulence, oralpathogenicity, and source joint. Alpha-defensin-negative samples served asuninfected controls. Median alpha-defensin levels were calculated for eachgroup, and Dunn's multiple comparison test for nonparametric data was used toidentify any statistically significant (p < 0.05) organism-specificdifferences in the alpha-defensin level.

RESULTS:

The alpha-defensin test for PJI waspositive in the setting of a wide spectrum of organisms typically causing PJI.The median alpha-defensin level for all 244 alpha-defensin-positive, culture-positivesamples (4.7 [interquartile range {IQR}, 3.7-5.3]) was higher than negativecontrols (0.26 [IQR, 0.22-0.33]) with a median difference of 4.4 (p <0.001). There were no differences in the median alpha-defensin levels whenperforming a multiple comparison test among Gram-positive organisms (4.7 [IQR,3.6-5.3]), Gram-negative organisms (4.8 [IQR, 4.2-5.3]), yeast (4.1 [IQR,2.2-5.1]), virulent organisms (4.7 [IQR, 3.8-5.2]), less virulent organisms(4.8 [IQR, 3.6-5.4]), oral pathogens (4.5 [IQR, 3.2-5.2]), knees (4.7 [IQR,3.7-5.3]), hips (4.9 [IQR, 4.1-5.8]), or shoulders (5.3 [IQR, 4.0-10.7]) withall comparisons having a p > 0.999.

CONCLUSIONS:

The alpha-defensin test providesconsistent results regardless of the organism type, Gram type, species, orvirulence of the organism and should be seriously considered to be a standarddiagnostic tool in the evaluation for PJI. Future research should focus on theperformance of this test in specific clinical scenarios such as the immediatepostoperative period in the setting of severe immunocompromise and in thesetting of a native joint.


群晓科苑

qbioscience.com




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