PATHOGENESIS

 Implanted foreign material is highly susceptible to local infection due to local immunodeficiency around the device. Infection occurs by either the exogenous or the hematogenous route. More rarely, contiguous spread from adjacent sites of osteomyelitis or deep soft-tissue infection may cause periprosthetic joint infection (PJI). The fact that foreign devices are covered with host proteins such as fibronectin favors the adherence of staphylococci and the formation of a biofilm that resists phagocytosis.

 EPIDEMIOLOGY

 The risk of infection manifesting during the first 2 postoperative years varies according to the joint. It is lowest after hip and knee arthroplasty (0.3–1.5%) and highest after ankle and elbow replacement (4–10%). The risk of hematogenous PJI is highest in the early postoperative period. However, hematogenous seeding occurs throughout life, and most cases therefore develop >2 years after implantation. The rate of risk for secondary PJI during S. aureus bacteremia is 30–40%.

MICROBIOLOGY

About 50–70% of cases of PJI are caused by staphylococci (S. aureus and coagulase-negative staphylococci), 6–10% by streptococci, 4–10% by gram-negative bacilli, and the rest by various other microorganisms. In patients with hematogenous PJI, the fraction of streptococci and gram-negative bacilli is higher and the fraction of coagulase-negative staphylococci is much lower. All microorganisms can cause PJI, including fungi and mycobacteria. C. acnes causes up to one-third of episodes of periprosthetic shoulder infection.

CLASSIFICATION AND CLINICAL MANIFESTATIONS

PJI is traditionally classified as early ( <3 months after implantation), delayed (3–24 months after surgery), or late ( >2 years after implantation). For therapeutic decision-making (see below), it is more useful to classify PJI as (1) acute hematogenous PJI with <3 weeks of symptoms, (2) early postinterventional PJI manifesting within 1 month after surgery, or (3) chronic PJI with symptom duration of >3 weeks.

Acute exogenous PJI typically presents with local signs of infection. In contrast, acute hematogenous PJI is most often caused by S. aureus and is characterized by new-onset pain. Local inflammatory signs are rare in hip PJI but frequent in knee PJI. Fever is rare after the initial phase of bacteremia. Key findings in chronic PJI are joint effusion, local pain, implant loosening, and occasionally a sinus tract. Chronic PJI is most commonly caused by low-virulence microorganisms such as coagulase-negative staphylococci or C. acnes. These infections are characterized by nonspecific symptoms, such as chronic pain caused by low-grade inflammation or early loosening.

DIAGNOSIS

 Blood tests such as the measurement of CRP (elevated levels, ≥10 mg/L) and erythrocyte sedimentation rate (elevated rates, ≥30 mm/h) are sensitive (91–97%) but not specific (70–78%). Synovial fluid cell counts are ~90% sensitive and specific, with threshold values of 1700 leukocytes/μL in periprosthetic knee infection and 4200 leukocytes/ μL in periprosthetic hip infection. A biomarker, α-defensin, can be tested in synovial fluid; this biomarker is highly specific and therefore useful in confirming PJI. However, this test is expensive and its sensitivity is limited; therefore, it should not be used for screening. During debridement surgery, at least three but optimally six tissue samples should be obtained for culture and histopathology. If implant mate rial (modular parts, screws, or the prosthesis) is removed, sonication of this material followed by culture and/or use of molecular methods to examine the sonicate fluid allows the detection of microorganisms in biofilms.

The three-phase bone scan is very sensitive for detecting PJI but is not specific. As mentioned above, this test does not differentiate bone remodeling from infection and therefore is not useful during at least the first year after implantation. CT and MRI detect soft tissue infection, prosthetic loosening, and bone erosion, but imaging artifacts caused by metal implants limit their use. ¹⁸F-fluorodeoxyglucose PET (¹⁸F-FD-PET) is an alternative method with good sensitivity but low specificity for the detection of PJI. Therefore, ¹⁸F-FDG-PET/CT is useful only in excluding but not confirming PJI.

اخر الاخبار

اخبار العتبة العباسية المقدسة

شعبة الخطابة تقيم مجلس عزاء بذكرى شهادة الإمام الحسن العسكري (عليه السلام)

قسم الشؤون الطبية يُنهي استعداداته لإحياء شهادة الإمام الحسن العسكري (عليه السلام) في سامراء

بالصور.. المؤمنون يتوافدون إلى سامراء لإحياء ذكرى شهادة الإمام الحسن العسكري (عليه السلام)

العتبة العباسية المقدسة تنشر لافتات العزاء بذكرى شهادة الإمام الحسن العسكري (عليه السلام)

المزيد

الآخبار الصحية

لا تبحث عن الدواء.. هذه الأطعمة كفيلة بإيقاف ألم الرأس

لا تترك زجاجة الماء في السيارة.. احذر شربها

عادة يومية.. كيف يؤثر تصفيف الشعر على جهازك التنفسي؟

احذر هذه الأطعمة.. تسرع الشيخوخة وتفقد بشرتك شبابها

المزيد

الآخبار التكنلوجية

الأوكتان وتأثيره: نصائح لحماية محرك سيارتك بكفاءة وأمان

حرب شهر سبتمبر تشتعل.. ماذا في جعبة أبل وسامسونغ؟

واتساب يطلق ميزة لتعديل الرسائل بالذكاء الاصطناعي

على الكوكب الأحمر.. ناسا تعثر على "قبعة الساحرة"

المزيد

مواضيع ذات صلة

Osteomyelitis in Long Bones

Vertebral Osteomyelitis

Human Hematopoietic Stem Cells

Embryonic Origin of Hematopoietic Stem Cells

نقي العظم (النخاع العظمي) Bone marrow

تكوين الدم Haematopoiesis

Gastrointestinal decontamination

تطبيقات البرايون ودوره المثير في مفهوم العقيدة المركزية

تصوير الأوعية التاجية

أدواء البريونات

Stages of Neutrophil Differentiation

Types of Bone