septic arthritis
Causes
Septic arthritis is an infection of the synovial joint space.
Septic arthritis can occur through hematogenous spread, local extension, or direct inoculation (trauma).
- S. aureus: most common, more than 50% of cases
- children > 2
- invasive procedures
- Streptococci
- S. epidermidis: foreign bodies, prosthetic joints
- N. gonorrhoeae: In young, sexually active patients who are otherwise healthy
- Salmonella: sickle cell disease
- P. aeruginosa and GNR: in IV drug users and diabetics
- fungal and candida infections: immunocompromised patients
Symptoms
- Acute onset, monoarticular
- Joints affected: knee > hip > wrists > shoulder > ankles
- triad: fever, joint pain, decreased ROM
Physical exam findings in septic arthritis include a warm, red, and tender joint with possible skin lesions over the affected area.
Diagnosis
- Serum:
- WBC count > 10,000
- ESR > 30
- CRP > 5
- Joint aspirate:
- Definitive: positive gm stain or culture
- Presumptive: WBC count > 50,000 with purulent fluid
- also shows a high neutrophil count and low glucose.
- Imaging: Ultrasound and MRI can help confirm joint effusion in septic arthritis.
Treatment
- 2 sets of blood cultures to assess origin
- surgical irrigation and drainage of the affected joint.
- Empiric abx:
- GPC: vancomycin
- GNC: ceftriaxone or fluoroquinolone
- GNR: 3rd/4th generation cephalosporins: ceftazidime, cefepime, pip-tazo, carbapenem
- Penicillinase-resistant penicillins: oxacillin, naficillin, cefazolin
- suspected pseudomonas: IV ceftazidime + IV aminoglycoside
- N gonorrhea: rocephin and azithromycin or doxy (for chlamydia), surgical drainage usually not necessary
- Tailor abx for 2 weeks
- concomitant bacteremia: at least IV 4 weeks
- endocarditis: tailor duration to endocarditis duration
Monitoring CRP is the best measure of treatment efficacy in cases of septic arthritis.