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.
Complications of septic arthritis
- Osteomyelitis: the spread of infection from the joint to the surrounding bone
- Permanent joint destruction
- Sepsis
What organisms are involved in (Prosthetic Joint) infections
CNS 27%
Enterococcus 14%
Staph aureus 25%
MRSA 7%
Others as well
Case study 1
57 year old lady
Severe Rheumatoid Arthritis
On Methotrexate, Prednisolone and Rituximab
Bilateral Knee Replacements 2007
Admitted May 2010
10 day history of L knee pain & swelling
Afebrile, systemically well
Tender, hot, swollen L Knee
Raised inflammatory markers
What investigations did she have?
X-Ray L knee joint -unremarkable
Joint aspirate
Fully Sensitive Corynebacterium spp
Identified as Listeria monocytogenes
Case study 1
57 year old lady
Severe Rheumatoid Arthritis
On Methotrexate, Prednisolone and Rituximab
Bilateral Knee Replacements 2007
Admitted May 2010
10 day history of L knee pain & swelling
Afebrile, systemically well
Tender, hot, swollen L Knee
Raised inflammatory markers
What was her management
4 weeks later - 1st stage revision
Cement - Gentamicin/Clindamycin with Vancomycin added
Discharged on 6 week course PO Amoxicillin
2nd Stage tissues all negative
Remains well almost 3 years out
Mechanism of infection for 51 year old lady with RA
Patient reported diarrhoeal illness 5 months previously. She had eaten soft cheeses after her Christmas Dinner!
Mechanism:
Transient Bacteraemi
Which bacteria is significant in Upper Limbs?
Propionibacteria
Why is propionibacteria more significant in the upper limbs?
They are colonisers of humans from the above the waist
Can even be shed by blinking the eyes
Therefore may represent more of a threat in upper limb prostheses and Spines
Suspect they are a very significant pathogen of upper limb surgery
Why is it so difficult to treat this?
Because they are slow growing!
Even contaminants take 7 days to grow
Longer when causing clinical infection (Upper limb and spines)
Because they rarely turn a broth cloudy
Frequently don’t trigger blood culture detection systems
You rely on finding them by Terminal subculture of prolonged broths
They are also very indolent organisms
Seldom cause acute infections
May not significantly raise inflammatory markers
