Septic arthritis Flashcards
What is septic arthritis
defined as the infection of 1 or more joints caused by pathogenic inoculation of microbes. It occurs either by direct inoculation or via haematogenous spread. It is a medical emergency!
Epidemiology of septic arthritis
- Septic arthritis is a rare but potentially devastating condition, affecting 5 per 100,000 people each year in the developed world
- Increases with age - 45% over 65 yrs
Aetiology of septic arthritis
- Staphylococcus aureus - the most common cause in all age groups
- Staphylococcus epidermidis - prosthetic joints
- Streptococcus pyogenes - children under 5 years old
- Neisseria gonorrhoeae - young, sexually-active adults
- Pseudomonas aeruginosa - immunosuppressed, eldery and IV drug abuse
- Escherichia coli - immunosuppressed, eldery and IV drug abuse
RF for septic arthritis
- Underlying joint disease:10-fold increased risk; conditions such as rheumatoid arthritis, osteoarthritis and gout
- Intravenous drug use:transfer of pathogenic organisms into the bloodstream
- Immunocompromised:elderly, diabetes, HIV
- Prosthetic joint
- Recent joint surgery
Why is septic arthritis a medical emergency?
due to the risk of permanent joint destruction, osteomyelitis and sepsis. It is most commonly caused by a bacterial infection, with the microbes either invading the joint directly or via the bloodstream from other sites of infection.
What are 90% of cases caused by for septic arthritis
90% of cases are caused bystaphylococci or streptococci, often as a complication of other pathologies such as cellulitis, chronic osteomyelitis, or drug abuse. Fungal and viral causes are rare.
Key presentations for septic arthritis
Septic arthitis mainly affects one joint and so should be suspected in all monoarthritic cases. The knee is most commonly affected, but hip, shoulder, wrist and elbow joints are also affected.
Signs for septic arthritis
- Hot, tender, erythematous, swollen joint
- In the elderly and immunosuppressed and in RA the articular signs may be muted
- Very limited range of movement
Symptoms in septic arthritis
- Difficulty weight bearing
- Fever
1st line investigation for septic arthritis
- FBC: leukocytosis
- CRP and ESR: elevated due to inflammation and used for monitoring response to treatment
- Blood cultures: should be performed onallpatients before commencing antibiotics
-
Joint aspiration (arthrocentesis): definitive investigation
Plain Xray
US or MRI
Gold standard investigation for septic arthritis
Joint aspiration - MSC
Scoring criteria for septic arthritis
Kocher criteria has been used in the diagnosis of septic arthritis. A score of 2 suggests a 40% probability and a score of 3 suggests a 93% probability.
Non weight bearing 1
Temp > 38.5 1
ESR > 40mm/hr 1
WCC >12x10(9)/L 1
DD for septic arthritis
Crystal arthropathies - gout and pseudogout
Management for Septic arthritis
IV antibiotics for 2 weeks followed by oral antibiotics for 4 weeks. Broad spectrum antibiotics should be given urgently and then tailored once the causative agent has been identified.
- Empirical therapy: flucloxacillin is first-line
- Penicillin allergy: clindamycin
- Suspected or confirmed MRSA: vancomycin
- Gonococcal arthritis or gram-negative infection: cefotaxime or ceftriaxone
- Joint drainage
- Aspiration
- Arthroscopic drainage
- Open drainage
Monitoring septic arthritis
After resolution of the acute illness, the patient should be followed up on at least one occasion to confirm complete recovery and to check for the presence of joint damage.
