Septic arthritis Flashcards
What are the differential diagnosis of acute monoarthritis?
1) Septic arthritis
2) Crystal arthritis: gout, pseudogout, apatite related
3) First presentation of inflammatory arthritis such as rheumatoid arthritis
4) Reactive arthritis
5) Intra- articular injury (fracture, meniscal tear)
6) Hemarthrosis
7) Metastatic carcinoma
What are the risk factors for acquiring septic arthritis?
Immunocompromised: >80yo, DM, cirrhosis, HIV, alcoholic
Diseased joint: chronically inflamed (eg RA/OA), prosthetic joints
For haem spread (majority): recent bacteraemia, recent endocarditis, recent skin infection, IVDU, IDC, central/peripheral lines
- Note: may not have bacteraemia at presentation: presumably transient/self-limited bacteraemia
- Note: in pt w no RF, w staph/strep/enterococci SA, think endocarditis!!
For direct inoculation: recent acupuncture or bite near joint/joint aspiration/ intra-art GC/ joint surgery/ open skin over joint
For contiguous spread: recent OM
What are the pathogens that cause septic arthritis?
Non-gonococcal
• Staph. aureus (>50%), GAS, GBS. Staph A is a very sticky organism and can seed to joints!
•Gram –ve rods (E. coli, Proteus, Klebsiella, Enterobacter)
• H. influenzae in children
Gonococcal (Neisseria gonorrhoea)
• Sexually active groups
• Has a more oligo/polyarticular, migratory pattern, w tenosynovitis and rash
•Blood and Joint Aspirate C/S are usually -ve -> Dx depends on HOPC, Hx + Mucosal swab C/S (urethral / cervical)
Usually monomicrobial (mostly staph), if polymicrobial think
- Penetrating trauma involving joint space
- Direct extension from bowel (eg ruptured diverticular) entering post thigh and hip joint via retroperitoneal space
What are the clinical features of septic arthritis?
Joint: acute onset monoarthritis - pain, swelling, redness, Inability to WB
- Usually Pain»_space;> Signs! With severe limitation in ROM
- Knee (~50%), hip, shoulder, elbow, ankle, Sternoclavicular Joint (esp IVDU)
- Rapid & Acute Onset, worsening over 3 days (unlike gout which is within 12-24 hrs)
- Typically Monoarticular (but can be polyarticular, except if DGI)
Systemic: fever (60%) (may not be observed in older pts), toxic and unwell
- This is not mandatory!
- Depending on aetiology, infection may be localised within joint and hence no systemic S&S
What are the investigations required for septic arthritis?
Joint aspirate: gold standard
- TWC + differential, Gram stain & c/s, glucose, AFB, polarised microscopy
- Presence of crystals DOES NOT RULE OUT SEPTIC ARTHRITIS!
- If fungal / TB suspected: Acid Fast Stain, Mycobacterial PCR & C/S, Fungal stain & C/S
- cloudy/purulent
- WBC >50K (>1.1K for prosthetic) diagnostic
- Glucose <60% serum level: just remember Low Glucose High Protein
Labs
- FBC: raised WBCs (left shift)
- Blood c/s
- CRP: usually >5
XR joint TRO concurrent joint disease / OM
2DE TRO IE if no clear source of infection in pts w known valvular heart disease/ polyarticular involvement
What is the management of septic arthritis?
Acute
1) Emp IV abx STAT aft joint aspiration
- Native joint (mostly Staph aureus): IV cefazolin (2nd line: IV cloxacillin, IV genta)
- If Penicillin allergy = Clindamycin
- Prosthetic joint : IV vancomycin – higher chance to be Staph A?
2) Surgical: irrigation and drainage of joint +- debridement
Post-acute
- Early PT: prevents stiffness, muscle wasting
- Monitor clinically w FBC, CRP
What is the clinical presentation of gonococcal arthritis?
1) RASH
2) SYSTEMIC S&S
3) MIGRATORY POLYARTHRITIS
4) TENOSYNOVITIS
Initial phase
- Fever and malaise: due to haematological spread of Gonorrhoea
- **Painless pustules/vesicles on peripheries
- *Migratory asymmetrical polyarthritis: Commonly affects knees, elbows, ankles, knees
- **Tenosynovitis: asymmetrical, affecting fingers, wrist, ankles, knees
- 40% have gonococcemia (+ve blood cultures)
Settling of initial phase
- Blood cultures become –ve
- NAATs (nucleic acid amplification tests) are a useful adjunct to cultures
Later phase
- Large joint monoarthritis or oligoarthritis
- Culture is usually +ve from genital tract, although joint fluid may be sterile
- Unclear distinction whether it is a septic arthritis or a response to bacterial LPS
What are the investigations required for gonococcal arthritis?
**sexual history
FBC
CRP
Blood c/s, joint aspiration (usually be sterile)
- +ve jnt aspirate culture only 25-30%
- +ve blood culture only 40%
Consider c/s of mucosal surfaces to increase yield: oral, urethral, cervical
- +ve culture of mucosal surface swabs (esp site of pri infection) is at 80%!
NAATs – much more sensitive than culture, can be done for Blood/Joint Aspirate/Mucosal Swab when cultures turn out negative!
What is the management of gonococcal arthritis?
Screen for concurrent Chlamydia infection (recall, the 2 predisposes each other) + screen for all other STIs
(TTSH) IV Ceftriazone + doxy (also covers for chlamydia). If resistant to ceftriazone: IV azithro
Joint rest
What are the clinical features of tuberculous arthritis?
- Spine (50%; Pott’s Dz) or hip/knee (30%) involvement, may affect mandible or vertebrae
- Febrile, night sweats, weight loss, anorexia
- Usual risk factors for TB apply: debility, excess alcohol use, immunosuppression, HIV/AIDs
What are the investigations required for tuberculous arthritis? ?
- Joint fluid c/s, synovium bx and c/s
- CXR to look for pTB
- Joint/spinal XR may show joint-space reduction and bone destruction if treatment delayed, but MRI spine detects abnorm earlier
- CT-guided bx from affected IV disc often needed to obtain c/s
