135.1 🎓 醫孞生版

135.1.0.1 📌 䞀頁重點

  • Acute monoarthritis = septic arthritis until proven otherwise (rule out gout/CPPD)
  • Joint aspiration is essential: cell count, Gram, culture, crystal
  • 病原:
    • Adult: S. aureus (#1), S. pyogenes, S. pneumoniae, Gram - (HCAI, immunocompromised)
    • Sexually active adults: N. gonorrhoeae (Disseminated Gonococcal Infection)
    • Children: K. kingae (< 4 yo), S. aureus, S. pyogenes
    • Prosthetic joint: CoNS, S. aureus
    • Animal bite: Pasteurella (cat), Eikenella (human)
    • Tick-bite (US): Borrelia burgdorferi (Lyme)
  • Empirical: Vancomycin + Ceftriaxone (cover MRSA + GN + DGI)
  • Drainage + 2-4 weeks IV antibiotic (longer for prosthetic / Mycobacterium / fungi)

135.1.0.2 1⃣ Joint Aspiration — Synovial Fluid Analysis

📖 䞭文抂念說明Joint aspiration 是 septic arthritis 的關鍵動䜜越早抜越奜。陷阱crystals (gout/CPPD) 與 septic arthritis 可同時存圚 — 看到結晶䞍胜攟心必須 Gram + culture confirm。Synovial WBC > 50,000 + PMN > 75% 是 septic 䞻芁 cutoff䜆有些 septic case WBC 范䜎臚床高床懷疑就芁當 septic 治療, 䞍胜單看敞字。Glucose 倧降 (vs serum) 是及䞀個 supporting clue。重點順序(1) 抜液 → (2) 立即 Gram stain (40-50% 陜性) + culture 送、(3) WBC + diff + crystal + glucose、(4) 䞍芁等結果立刻 empirical Vanco + Ceftriaxone + drain。

Parameter Normal Inflammatory Septic Crystal
Color Clear Yellow Cloudy/purulent Yellow
WBC < 200/ÎŒL 2,000-50,000 > 50,000 (often 100K+) Variable, often > 50K (overlap!)
PMN% < 25% > 50% > 75-90% > 50%
Glucose Equal serum Slightly low Often very low Normal
Crystals None None None (usually) MSU (gout) or CPPD (pseudogout)
Gram + culture None None Positive ~40-50% Gram, 90% culture None

⚠ Crystals + septic 可同時存圚 — 必須 gram + culture confirm

135.1.0.3 2⃣ 病原 + Empirical

135.1.0.3.1 Native Joint, Healthy Adult
颚險 病原
Default (sexually active) N. gonorrhoeae (DGI) + S. aureus + Strep
Older / immunocompromised / IVDU S. aureus (incl MRSA) + GN
Crystalline diagnosis: but septic until proven
135.1.0.3.2 Empirical Treatment
  • Vancomycin + Ceftriaxone (covers MRSA + DGI + most pathogens)
  • IVDU/HCAI: Vancomycin + Pip-tazo or Cefepime
  • After culture: narrow spectrum
135.1.0.3.3 Prosthetic Joint
  • Acute (< 3 mo post-op): S. aureus, GNs
  • Late: CoNS, S. aureus, S. viridans
  • Treatment: 1-2 stage revision + antibiotic 6-8 weeks (++ rifampin for staph)
135.1.0.3.4 Disseminated Gonococcal Infection (DGI)
  • 1-3% gonorrhea → DGI
  • Triad (varied):
    1. Tenosynovitis (asymmetric, hands/feet/wrist/ankle)
    2. Migratory polyarthralgia (transient)
    3. Dermatitis (pustular/papular skin lesions)
  • Often Joint aspiration culture-negative (~ 50%)
  • PCR of urethra, cervix, throat, rectum → 高 yield
  • Treatment: Ceftriaxone 1g IV daily × 7-14 d, then PO step-down
  • + Doxycycline or Azithromycin to cover concomitant Chlamydia

135.1.0.4 3⃣ Drainage + 持續

135.1.0.4.1 Drainage methods
  • Daily aspiration (large joint): traditional, but tedious
  • Arthroscopic / Open lavage: hip, complex, prosthetic, refractory
  • Hip septic arthritis → 緊急 OR drainage (within 6 hr) — 因為 hip joint compartment 高壓 → cartilage 損害快
135.1.0.4.2 Duration
  • Native joint, S. aureus: 2-4 weeks IV
  • Native joint, Gram - / GAS: 2 weeks
  • Native joint, DGI: 7-14 days
  • Prosthetic joint: 6-8 weeks + retention (if amenable) + chronic suppression
  • Mycobacteria/fungi: months-years

135.1.0.5 4⃣ Special Causes

135.1.0.5.1 Lyme Arthritis
  • Borrelia burgdorferi (US northeast/midwest, EU, increasingly worldwide)
  • Late manifestation (months after EM rash, untreated)
  • Mono- or oligoarthritis of large joints (knee most), recurrent
  • Diagnosis: serology (ELISA → Western blot, two-tier)
  • Treatment: doxycycline 100 mg BID × 28 d (oral); ceftriaxone IV if neuro/refractory
135.1.0.5.2 Tuberculosis Arthritis
  • Hematogenous from primary TB (often years later)
  • Mono-arthritis, slow progression, often spine (Pott’s disease) > peripheral joints
  • Diagnosis: synovial biopsy + AFB culture + GeneXpert MTB
  • Treatment: 4-drug RIPE × 2 mo + 7 mo INH/RIF (= 9 month total)
135.1.0.5.3 Fungal Arthritis
  • Candida: prosthetic joint, CRBSI, IVDU
  • Sporotrichosis: gardener (rose thorn)
  • Coccidioides, Histoplasma, Blastomyces: endemic mycosis
  • Treatment: amphotericin B → azole; long course (months)
135.1.0.5.4 Reactive Arthritis (Reiter’s)
  • Post-infectious (not direct infection): GI (Yersinia, Campylobacter, Salmonella), GU (Chlamydia)
  • 1-4 weeks after primary
  • Triad: arthritis + uveitis/conjunctivitis + urethritis
  • HLA-B27 association
  • Treatment: NSAIDs + treat primary infection + DMARDs if persistent