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1、假体关节相关感染A 62-year-old woman with osteoarthritis presents with a 7-month history of progressively worsening left hip pain radiating to the groin, 8 months after undergoing total left-hip arthroplasty. The pain has not responded to nonsteroidal anti-inflammatory drugs. Physical examination reveals a s
2、inus tract overlying her left hip. Her leukocyte count is 8000 per cubic millimeter, and the C-reactive protein (CRP) level is 15.5 mg per liter. A radiograph shows loosening of the prosthesis at the bonecement interface. Synovial-fluid aspirate shows 15103 cells per cubic millimeter (89% neutrophil
3、s); cultures of an aspirate from the hip grow Staphylococcus epidermidis. How should her case be managed? 1名62岁女性骨性关节炎患者，左侧THA术后8个月，左髋渐进性疼痛并向腹股沟放射7个月。服用非甾类抗炎药疼痛无缓解。查体示左髋有一窦道形成。白细胞计数为8000个/mm3，C-RP为15.5mg/L。放射线检查示假体和骨水泥界面有松动。关节液检查示15X103个细胞/mm3，中性粒细胞比例为89；关节炎培养示为表皮葡萄球菌阳性。该如何对这一病例进行处理？The Clinical Pro
4、blemThe numbers of primary total hip and total knee arthroplasties have been increasing over the past decade, with nearly 800,000 such procedures performed in the United States in 2006 (Fig. 1A).1 Procedures to replace the shoulder, elbow, wrist, ankle, temporomandibular, metacarpophalangeal, and in
5、terphalangeal joints are less commonly performed.临床问题：过去10年间，行首次髋膝关节置换的病例数有了大幅的增长，到2006年美国约进行了800000例此类手术。而行肩、肘、腕、踝、颞下颌、掌指和指间关节置换则少见的多。Prosthetic joints improve the quality of life, but they may fail, necessitating revision or resection arthroplasty. Causes of failure include aseptic loosening, infe
6、ction, dislocation, and fracture of the prosthesis or bone. Infection, although uncommon, is the most serious complication, occurring in 0.8 to 1.9% of knee arthroplasties3-5 and 0.3 to 1.7% of hip arthroplasties.5-7 The frequency of infection is increasing as the number of primary arthroplasties in
7、creases (Fig. 1B).2 Patient-related risk factors for infection include previous revision arthroplasty or previous infection associated with a prosthetic joint at the same site, tobacco abuse, obesity, rheumatoid arthritis, a neoplasm, immunosuppression, and diabetes mellitus. Surgical risk factors i
8、nclude simultaneous bilateral arthroplasty, a long operative time (2.5 hours), and allogeneic blood transfusion, and postoperative risk factors include woundhealing complications (e.g., superficial infection, hematoma, delayed healing, wound necrosis, and dehiscence), atrial fibrillation, myocardial
9、 infarction, urinary tract infection, prolonged hospital stay, and S. aureus bacteremia.3-6,8-11假体关节能够提高患者的生活质量，但是一旦失败则必须进行翻修或是截骨矫形术。导致失败的原因包括了无菌性松动、感染、脱位和假体或是假体周围的骨折。感染虽不常见，但是却是最为严重的并发症，在膝关节置换中其发生率约为0.3-0.7，在髋关节置换中约为0.3-1.7。随着初次关节置换手术量的增加，术后感染的发生率也有所上升。与患者相关的感染危险因素包括同一关节已行翻修手术或是已发生过假体关节相关感染、吸烟、肥胖、类
10、风湿性关节炎、有赘生物、免疫抑制和未控制的糖尿病等。而手术相关的危险因素包括了同期行双侧置换、手术时间长（大于2.5小时）以及输血等。术后的感染危险因素包括伤口愈合相关并发症（表浅感染、血肿、延迟愈合、泌尿系感染、住院时间延长以及金葡菌菌血症等。Staphylococci (S. aureus and coagulase-negative staphylococcus species) account for more than half of cases of prosthetic-hip and prosthetic-knee infection12 (Fig. 2). S. aureus
11、 infection is particularly common in patients with rheumatoid arthritis.13 Other bacteria and fungi cause the remainder of cases.14,15 Propionibacterium acnes is a common cause of infection associated with shoulder arthroplasty.16 Up to 20%of cases are polymicrobial, most commonly involving methicil
12、lin-resistant S. aureus (MRSA) or anaerobes.17 Approximately 7% of cases are culture-negative, often in the context of previous antimicrobial therapy.18葡萄球菌（金葡菌和凝血酶阴性类葡萄球菌）约与半数髋膝假体相关感染有关。金葡菌感染在类风湿性关节炎患者中尤为常见。剩余的感染病例则是由其他细菌或真菌引起的。丙酸菌属粉刺是造成肩关节置换感染的常见原因之一。有高达20的感染病例是由多处微生物感染引起的，其中多包括了MRSA（甲氧西林耐药金葡菌）或是厌
13、氧菌。接近7的病例是关节炎培养阴性的，此类病例多是已经接受过抗生素治疗的患者。The pathogenesis of infection associated with a prosthetic joint involves interactions among the implant, the hosts immune system, and the involved microorganism or microorganisms. Only a small number of microorganisms is needed to seed the implant; such organi
14、sms adhere to the implant and form a biofilm in which they are protected from conventional antimicrobial agents and the host immune system.19 Associated microorganisms are often skin bacteria that are inoculated at joint implantation. In some cases, organisms seed the implant hematogenously or throu
15、gh compromised local tissues.假体关节相关感染的发病机制涉及到内置物、宿主免疫系统和微生物三方面的相互作用。只需极少量的微生物种植于内置物上就能引起感染，微生物粘附在内置物上，并在其表面形成1层生物膜，这可以使微生物抵抗传统抗生素和宿主免疫系统。Infection with virulent organisms (e.g., S. aureus and gram-negative bacilli) inoculated at implantation is typically manifested as acute infection in the first 3
16、months (or, with hematogenous seeding of the implant, at any time) after surgery, whereas infection with less virulent organisms (e.g., coagulase-negative staphylococci and P. acnes) is more often manifested as chronic infection several months (or years) postoperatively. The most common symptom of infection associated with a prosthetic joint is pain. In acute infection, local signs and symptoms (e.g., severe pain, swelling, erythema, and warmth at the infected
