Infectious arthritis

Introduction to Infectious Arthritis Joint infections are inflammations caused by bacteria, fungi or viruses that are derived from the synovial membrane or tissues surrounding the joints. The incidence of infectious arthritis varies widely worldwide: in the United States, the incidence rate is <200/100,000, and the incidence in European countries is low (<5/100,000 in Switzerland, but in Africa, Latin America and Asia) The incidence is higher. 50% of children with infectious arthritis are those <2 years old. In these cases, 93% involve unilateral joints, especially lower extremity joints such as knee joints (39%), hip joints ( 26%) and ankle joint (13%). The source of infection is otitis media, umbilical inflammation, central neuritis, femoral vein puncture, meningitis and adjacent osteomyelitis. basic knowledge The proportion of sickness: 0.01% Susceptible people: no specific population Mode of infection: non-infectious Complications: fracture osteomyelitis

Causes of infectious arthritis

Neisseria gonorrhoeae infection (20%):

The most common among adults is Neisseria gonorrhoeae, which spreads from the mucosal surface (cervix, rectum, and pharynx) to some small joints, wrists, elbows, knees, and ankles. Less involved.

Staphylococcal infection (28%):

Non-gonococcal arthritis is mostly caused by Staphylococcus aureus (45%), Streptococcus (9%), and Gram-negative bacteria such as Enterobacter, Pseudomonas aeruginosa (40%), Serratia 5%) caused by Gram-negative infections in young people and the elderly, especially those with severe trauma or serious medical diseases (such as kidney failure or kidney transplantation, joint repair, SLE, RA, diabetes, malignant diseases) and Drug users, the majority of infections in the urethra or skin, 80% of patients, non-gonococcal arthritis found in unilateral joints (knee, hip, shoulder, wrist, ankle, elbow), multiple joints Patients with bacterial infectious arthritis are often accompanied by chronic arthritis (RA, osteoarthritis) or a displaced joint. Rotabacterium is the causative agent of Lyme disease, causing acute migratory joint pain accompanied by fever. , headache, fatigue and skin damage or intermittent monoarthritis.

Anaerobic infection (15%):

Joint infection anaerobic bacteria are often accompanied by facultative or aerobic infections (5% to 10%), such as Staphylococcus aureus, Streptococcus mutans and Escherichia coli, dominant anaerobic bacteria such as Propionibacterium acnes, Streptococcus Clostridium and Bacteroides can infect joints during joint repair, trauma or early surgery, and the susceptibility factors for anaerobic infections are: penetrating injury, joint puncture, recent surgical history, joint repair, proximity Infection, diabetes and malignant tumors.

Etiology

1. Acute infectious arthritis (95%) can be caused by bacterial or viral infections.

(1) Staphylococcus aureus and group B streptococcal infections are more common in neonates and children over 2 years of age. Among the children under 2 years of age, Kingella Kingae is the most common, although Haemophilus influenzae type B is An important causative agent of bacterial arthritis in children between 6 months and 2 years of age. Since immunization has reduced the incidence of children under 5 years of age by 95%, in children, bacterial arthritis caused by Neisseria gonorrhoeae <10%, but it is still a major cause of polyarticular infections.

(2) Joint infection caused by bite is caused by Gram-negative bacteria such as Streptococcus B, oral anaerobic bacteria (such as Clostridium, Streptococcus, Bacteroides), caused by animal bites Joint infections are often Staphylococcus aureus or oral flora, and Pasteurella infection accounts for 1/2 after dog and cat bite. Dogs and cats can also cause Pseudomonas, Moraxella and blood-sucking after biting. Bacillus infection, after the mouse bite can cause infection with Actinobacillus actinomycetes or small spirulina.

(3) Joint infections in HIV patients are often caused by Staphylococcus aureus, Streptococcus, and Salmonella. HIV patients may have Reidel syndrome, recurrent arthritis, HIV-associated arthritis and joint pain. The longer HIV patients survive, The more chances of infection by mycobacteria, fungi and rare conditional pathogens.

(4) Viruses causing acute arthritis include parvovirus B19, HBV, HCV, rubella virus (after acute infection and immunization) and coat virus, varicella virus, parotid virus (adult), adenovirus, coxsackie virus (A9) , B2, B3, B4, B6); Epstein-Barr virus is also associated with joint pain, arthritis, and is more likely to cause polyarthritis than bacteria.

2. Chronic infectious arthritis

Chronic arthritis (5%) can be caused by mycobacteria, fungi and other less pathogenic bacteria such as Mycobacterium tuberculosis, Mycobacterium marinum, Mycobacterium kansii, Candida, and cool spores. Genus, capsular histoplasma, Cryptococcus neoformans, dermatitis, sclerotium, Aspergillus, Actinomyces and Brucella.

Two-thirds of patients have joint infections within 1 year after surgery, which may be due to surgery to introduce bacteria or postoperative bacterial infections such as skin infections, pneumonia, dental infections or UTI. Early joint replacement infections are purely gold Staphylococcus aureus accounts for 50%, mixed infections account for 35%, Gram-negative bacteria account for 10%, and anaerobic infections account for 5%.

Pathogenesis

Joint infections trigger an inflammatory response (arthritis) that kills microbes but also damages joint tissue.

The source of infection reaches the joint by: (1) direct dissemination (injury, surgery, injection, bite); (2) adjacent infection into the joint (such as osteomyelitis, soft tissue abscess, infected wound); (3) blood transmission Infected lesions of the skin, respiratory system, urinary system and digestive system reach the synovial membrane through the blood circulation.

Infected microorganisms are concentrated in synovial fluid and synovial tissue, and virulence factors such as adhesion factors can cause bacteria to colonize joint tissues, such as adhesion factors produced by Staphylococcus aureus, endotoxin produced by Gram-negative bacteria. (lipopolysaccharide), cell wall skeleton component, exotoxin produced by Gram-positive bacteria, immune complexes produced by binding of bacterial antigens and antibodies, all promote inflammation, and multinucleated neutrophils (PMN) migrate into joints and phagocytose pathogens. The lysosomal enzyme released by PMN at the same time of phagocytosis also causes damage to the synovial membrane, ligament and cartilage. Therefore, PMN is an important defense line for the host and also a major cause of acute bacterial arthritis. Secondly, chronic infection (such as RA) ), the synovial membrane can be regenerated and repaired (formation of vasospasm) and causes damage to articular cartilage and subchondral bone. Even if antibiotics are used to control infection, synovial inflammation continues to exist. It is theorized that infection causes cartilage to become antigen and supplemented with bacterial components. Participate in immune regulation, causing reactive synovitis.

Infectious arthritis prevention

For the prevention of this disease and to do the following points:

(1) Preventive treatment seems to be only suitable for patients with increased susceptibility to skin infections, urogenital tract and respiratory tract infections, and for patients undergoing microinvasive surgery, prophylactic treatment is only suitable for highly susceptible patients.

(2) Antibiotics were selected by drug sensitivity test, and the whole body was continuously applied for several weeks until the infection was controlled and calmed down.

(3) Properly moving joints to prevent adhesions, but those with longer course of disease, due to the serious destruction of articular cartilage and joint bone, often turn into osteoarthrosis after inflammation control, and the function is difficult to recover.

Infectious arthritis complications Complications, osteomyelitis

The disease can often cause several complications:

1, pathological fractures.

2, limb growth disorders, such as osteophyte destruction, limb growth length is affected, the affected limb becomes shorter; or due to inflammation near the epiphysis, blood supply is rich, so that the epiphysis grows faster, the affected limb is slightly longer, and sometimes due to partial involvement of the epiphysis, Form abnormal growth, such as knee varus or eversion.

3, joint contracture and rigidity.

4. Traumatic osteomyelitis often has delayed fracture and disconnection due to infection, and limited joint activity.

Infectious arthritis symptoms Common symptoms Joint hard joint swelling urate in the joint... Compensatory lumbar lordosis synovial thickening heat pain ESR increased bacterial infection

Symptoms and signs

Joint infections can be acute, sudden swelling of the joints, or chronic manifestations: mild symptoms, insidious onset.

Acute bacterial arthritis (1 hour to several days), severe joint pain, fever and tenderness with limited exercise. Patients with other symptoms can cause misdiagnosis. Children with infectious arthritis appear as one limb. Active exercise restriction (false sputum), irritating normal body temperature or low fever. Acute bacterial arthritis in adults is divided into gonococcal and non-gonococcal, the clinical manifestations and treatment responses are not the same.

Neisseria gonorrhoeae is caused by Neisseria gonorrhoeae, with typical dermatitis-arthritis-tenosynovitis syndrome. Diffusion of gonococcal infection is characterized by fever of 5 to 7 days, chills, skin lesions (freckles, papules, Pustules, blood blisters, gangrene) are more common on mucosal surfaces, trunk and lower extremities, migratory joint pain, tenosynovitis, involving one or more joints. However, lack of mucosal infection, Neisseria gonorrhoeae can also cause arthritis-dermatitis Syndrome, accompanied by upper respiratory tract infection or meningitis and severe shock state.

Non-gonococcal infectious arthritis usually involves a single joint with moderate to severe pain. Exercise or pressurization can exacerbate pain and thus manifest as exercise limitation. Most of the affected joints are red, swollen, and hot. 50% of patients have normal body temperature. Or have low fever, 20% of patients have chills.

Most anaerobic infections are monoarthritis, which can easily affect the hip or knee joint (50%). Anaerobic infections outside the joint include abdominal genitalia, periodontal abscess, sinusitis, ischemic limb inflammation and acne.

The joint infection caused by drug users mainly involves the central axis bone (thoracic clavicle, hip bone, shoulder joint, spine, pubic symphysis, ankle joint), and may also involve the joints of the extremities. Gram-negative bacteria are often painless. More violent staphylococcal infections are difficult to diagnose.

After a person bite, the joint infection is mostly painless. After a week, the symptoms appear. After the cat and the dog bite, the redness, swelling and pain of the hand joint will appear within 24 hours. After the mouse bites, there will be fever, rash, joint pain and Local lymphadenopathy (latency of 2 to 10 days).

Joint infection caused by replacement joints can lead to loosening of the replacement, failure and abscess. There is a high incidence and mortality. Within 1 year after surgery, there are many postoperative wound infections that last for several months, repairing joints at rest Or pain when bearing weight. Nearly one-third of patients with surgery have joint infections after 1 year, mostly caused by bacteremia caused by extra-articular infection sources (such as pneumonia, UTI, skin infection, periodontitis, device injury). 25% of patients had joint pain, had a history of wrestling within 2 weeks, and 20% had a history of surgery. The patient may have no fever or leukocytosis, but the erythrocyte sedimentation rate is accelerated.

The onset of chronic bacterial arthritis is insidious, the joints are slightly swollen, and the local skin temperature is slightly elevated and red, and the pain is mild. .

Infectious arthritis examination

(1) 1/2 cases can show increased white blood cell count, increased erythrocyte sedimentation rate and increased C-reactive protein.

(2) In the synovial fluid samples of acute infected swollen joints, the WBC count is >20000/l (usually >100000/l), the neutrophils are >95%, the synovial fluid viscosity and sugar content are decreased, and the Gram stain can be Identification of 50% to 75% of Gram-negative and Gram-positive bacteria in joint infections, but can not distinguish between Staphylococcus and Streptococcus, synovial fluid also requires anaerobic and aerobic culture, synovial odor or X-rays have gas shadows inside or around the soft tissue, suggesting an anaerobic infection.

(3) 99m sacral scan

Abnormal manifestations can be seen in infectious arthritis, especially in the axial skeletal joints. The scan shows that the synovial membrane is rich in blood flow, the intake is increased, the bone metabolism is accelerated, and the results are positive in aseptic and bacterial arthritis, but The accuracy of 99m is only 77%. Because the vasoconstriction and vascular network are not formed, the vascular embolization will offset the increase in intake caused by infection. The accuracy of 67 gallium scan can reach 91%, but its radiation dose is large, earlier. Infection can be seen in ischemic cold spots, gallium scan (or indium-labeled WBC or antibody) increased in the intake of suppurative synovial fluid, acute infection is more sensitive than chronic infection, sensitivity of gallium scan in replacement joint infection Low, indium-labeled WBC scans have not been verified.

Diagnosis of infectious arthritis

diagnosis

Diagnosis of infectious arthritis should be highly suspicious, especially if there are non-articular exogenous infections, because the symptoms of various arthritis are similar, clinical manifestations and microbiological examination of the infected site are conducive to diagnosis, 1/2 Cases can show increased white blood cell count, increased erythrocyte sedimentation rate and increased C-reactive protein.

(1) In the synovial fluid samples of acutely infected swollen joints, the WBC count is >20000/l (usually >100000/l), the neutrophils are >95%, the synovial fluid viscosity and sugar content are decreased, and Gram stain can be used. Identification of 50% to 75% of Gram-negative and Gram-positive bacteria in joint infections, but can not distinguish between Staphylococcus and Streptococcus, synovial fluid also requires anaerobic and aerobic culture, synovial odor or X-rays have gas shadows inside or around the soft tissue, suggesting an anaerobic infection.

(2) Sexually active patients with a typical medical history should be highly suspected of gonococcal infection, especially when gonorrhea is diagnosed elsewhere. Because gonococcal is sensitive to dryness, it is difficult to culture. If it is suspected to be disseminated gonococcal infection, blood samples and slippery can be taken. The liquid is immediately inoculated on a non-selected chocolate plate. In addition, samples collected from the cervical mucosa, rectum, urethra, and pharynx can also be selected for culture. In the first week, 60% to 75% of the blood culture is positive, which can be used as a positive result. The only diagnosis is that the early tenosynovitis has a negative culture result, and the synovial culture results of septic septic arthritis are mostly positive, and the secretion culture of skin damage may also have a positive result.

(3) The only manifestations of early acute bacterial arthritis on the X-ray are swelling soft tissue shadows and synovial fluid leakage. After 10-14 days of bacterial infection, the joint space is narrowed (reactive joint cartilage destruction), subchondral bone erosion and The signs of osteomyelitis appear. Gas in the joint cavity indicates that E. coli and anaerobic bacteria are infected. The joint space of chronic bacterial arthritis increases, and edge bone corrosion and osteosclerosis occur.

(4) 99m sacral scan showed abnormal manifestations in infectious arthritis, especially in the axial skeletal joints. The scan showed that the synovial membrane was rich in blood flow, the intake increased, and the bone metabolism was accelerated in the aseptic and bacterial joints. Inflammation is positive, but the accuracy of 99m is only 77%. Because of vasoconstriction, vascular network is not formed, vascular embolization will offset the increase in intake caused by infection. The accuracy of 67 gallium scan can reach 91%, but its The radiation dose is large, the early infection shows ischemic cold spot, the gallium scan (or WBC or antibody labeled with indium) increases the intake of suppurative synovial fluid, and the acute infection is more sensitive than the chronic infection, in the replacement joint The sensitivity of gallium scans in infection is low, and indium-labeled WBC scans have not been validated.

Differential diagnosis

The disease needs to be differentiated from rheumatoid arthritis, and the infectious arthritis itself has the following characteristics to help distinguish it from rheumatoid arthritis:

1, mostly involving single joints, occasionally more than two, showing asymmetry.

2, acute onset, joint pain is more severe, systemic symptoms are obvious.

3, joint cavity puncture can extract pus, culture can detect pathogenic bacteria.

4. The rheumatoid factor is negative and the immune test is normal.

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