Septic Joint

1. Causes
   1. See Septic Joint Causes
2. Risk Factors
   1. Immunosuppression
   2. HIV Infection
   3. Alcoholism
   4. Sickle Cell Anemia
   5. Inflammatory Bowel Disease
   6. Prosthetic Hip Joint
   7. Prosthetic Knee Joint
   8. Skin Infection (especially cutaneous ulcers)
   9. Joint surgery
   10. Rheumatoid Arthritis
   11. Elderly patients over age 80 years old
   12. Diabetes Mellitus
   13. Intravenous drug use (unusual joints affected)
   14. Large vein catheterization (unusual joints affected)
   15. Kaandorp (1995) Arthritis Rheum 38:1819-25
3. Pathophysiology
   1. Hematologic seeding in most cases
4. Precautions
   1. Septic Arthritis has a had inpatient mortality (approaches 15%)
   2. Examination is unreliable in ruling out Septic Arthritis
      1. Poor reliability in distinguishing from Gouty Arthritis
      2. Crystals in Synovial Fluid does not exclude Septic Joint (actually increases its risk)
   3. Lab testing (outside of joint aspiration) is unreliable
      1. No lab value outside of Joint Fluid examination excludes Septic Joint
5. Differential Diagnosis
   1. See Monoarticular Arthritis
   2. See Joint Pain Causes (Monoarticular)
6. Symptoms: Presentations in newborns
   1. Fever only present in 24-50% of cases
   2. Ill appearance
   3. Decreased use of the affected extremity
7. Signs and symptoms
   1. Rapid onset monoarticular joint inflammation
      1. Joint Pain with motion (Test Sensitivity 100%, but poor Specificity)
      2. Joint swelling
      3. Joint warmth (unreliable)
      4. Joint erythema
      5. Significantly decreased joint range of motion
      6. Limb paralysis from inflammatory neuritis
   2. Joints affected in bacterial infection
      1. Septic Knee (50% of cases)
      2. Septic Hip (especially in young children)
      3. Septic Ankle
      4. Septic Shoulder
      5. Septic elbow
   3. Joints affected with intravenous Drug Abuse
      1. Sacroiliac joint
      2. Sternoclavicular joint
      3. Symphysis pubis
      4. Vertebral disc spaces
8. Labs: General
   1. Precaution
      1. None of these labs (CBC, ESR nor CRP) absolutely excludes Septic Arthritis at any level
         1. These labs may all be normal or even low despite Septic Arthritis
         2. Lab markers are useful as baseline to follow response to therapy
      2. Arthrocentesis is the only accurate method to exclude Septic Arthritis
   2. Erythrocyte Sedimentation Rate (ESR)
      1. ESR typically > 25 mm/hour in pediatric Septic Arthritis
   3. C-Reactive Protein (C-RP)
      1. C-RP typically >20 mg/L in pediatric Septic Arthritis
      2. Closely mirrors infectious, inflammatory process
      3. Test Sensitivity: 95% in children
   4. Complete Blood Count
      1. WBC Count typically >12,000 in pediatric Septic Arthritis
9. Labs: Synovial Fluid Exam via arthrocentesis
   1. Synovial Fluid culture is imperative
   2. See Synovial Fluid White Blood Cell Count
   3. Avoid Joint FluidGlucose and protein (not useful)
   4. Bacterial arthritis
      1. Opaque to turbid Synovial Fluid
      2. Synovial Fluid WBC
         1. Non-prosthetic joint: >50,000 White Blood Cells (>90% PMNs)
            1. Likelihood Ratio: 4.7 for Septic Arthritis
         2. Prosthetic joint: >1700 White Blood Cells per mm3 (or >65% PMNs)
      3. Gram Stain
         1. Test Sensitivity: 29-60%
      4. Bacterial Culture
         1. Test Sensitivity: 30-50% (75% if polyarticular)
         2. Guides antibiotic therapy when positive
      5. Synovial lactate
         1. Synovial lactate >10 mmol/L has a very high Likelihood Ratio for Septic Arthritis (rules in Septic Arthritis)
   5. Gonococcal Arthritis
      1. Clear to opaque Synovial Fluid
      2. Synovial Fluid WBC: 30,000 to 100,000 (>80% PMNs)
      3. Gram Stain Positive in <25% of cases
      4. Culture positive in <50% of cases
   6. Tuberculous Arthritis
      1. Opaque Synovial Fluid
      2. Synovial Fluid WBC: 10,000 to 20,000 (>50% PMNs)
      3. Gram Stain Positive in <20% of cases
      4. Culture positive in 80% of cases
10. Imaging
    1. Joint Xray
       1. Early changes
          1. Distention of joint capsule
          2. Joint Dislocation
       2. Late changes
          1. Joint space destruction
          2. Epiphyseal cartilage resorption
          3. Metaphysis Erosion
    2. Joint Ultrasound
       1. Indentifies effusion
       2. Guides aspiration
    3. Advanced imaging
       1. CT or MRI joint for unclear diagnosis
11. Imaging: Possibly Infected Prosthetic Joint
    1. Nuclear scan
       1. Negative Nuclear scan excludes septic prosthetic joint
    2. Pet Scan
    3. Avoid CT Scan or MRI in infected prosthetic joint
       1. Does not distinguish infected prosthetic joint from other causes of pain
12. Management: General
    1. Septic Arthritis management requires two components
       1. Thorough Joint Fluid drainage of purulent fluid
       2. Antimicrobial management to cover the causative organisms
    2. Antibiotics are started after obtaining joint culture and Blood Culture
       1. Gram Stain of fluid may assist antibiotic selection
       2. Empirically antibiotics based on age and risk factors (see below) until culture results available
       3. Antibiotics do not need to be injected into joints
       4. Antibiotics may be considered prior to arthrocentesis if
          1. Strong suspicion of Septic Arthritis AND
          2. Difficult arthrocentesis requiring intervention radiology or rheumatology and that procedure is delayed >24 hours AND
          3. Consultant agrees that antibiotics should be started before the culture has been obtained
    3. Corticosteroids
       1. Discuss with consultant (orthopod)
       2. Associated with decreased duration and Disability in studies of pediatric Septic Arthritis
       3. Odio (2003) Pediatr Infect Dis J 22(10): 833-8
13. Management: Surgical
    1. Joint aspiration
       1. Repeat for reaccumulation of fluid as needed up to once to twice daily
       2. Consider saline lavage
    2. Open Surgical drainage indications
       1. Difficult joint aspiration access (e.g. hip)
       2. Persistent fever and symptoms >24 hours
       3. Leukocytosis persists beyond 48 to 72 hours
       4. Repeat blood or joint cultures positive >48 hours
       5. Infected joint prosthesis
          1. Prosthesis may be salvaged if infection <1-2 weeks
             1. Many infected prostheses may still need to be removed
          2. Surgically debride the infection
          3. Treat with parenteral combination antibiotic therapy for 4 weeks (equivalent outcomes to 6 weeks of therapy)
             1. Use Rifampin as part of antibiotic regimen
14. Management: Antibiotics for Infants (age <3 months)
    1. See Septic Arthritis Causes
    2. Empiric antibiotics (2 drug regimen)
       1. Drug 1: Vancomycin 40 mg/kg divided q6-8 hours IV
       2. Drug 2: Cefotaxime 50 mg/kg IV q8 hours
    3. Modify antibiotic selection based on Blood Culture (positive in a majority of cases)
    4. Assume Osteomyelitis of adjacent bone (occurs in two thirds of cases)
15. Management: Antibiotics for Child (3 months to 14 years)
    1. See Septic Arthritis Causes
    2. Primary regimen
       1. Two drug regimen (most cases)
          1. Drug 1: Vancomycin 40 mg/kg divided q6-8 hours IV
          2. Drug 2: Cefotaxime 50 mg/kg IV q8 hours
       2. One drug regimen (if Gram Stain only with Gram Negative organisms)
          1. Cefotaxime 50 mg/kg IV q8 hours
    3. Alternative regimen (2 drug regimen)
       1. Drug 1: Aztreonam 30 mg/kg IV q6 hours
       2. Drug 2: Choose one
          1. Clindamycin 7.5 mg/kg IV q6 hours or
          2. Linezolid 10 mg/kg IV q8 hours
    4. Modify antibiotic selection based on Blood Culture
    5. Duration of therapy is typically 30 days
       1. Ten days may be adequate in quickly resolving symptom, signs and C-RP
       2. Peltola (2009) Clin Infect Dis 48:1201–10
16. Management: Antibiotics for Adolescent and Adult (age over 14 years)
    1. Acute monoarticular with STD risk
       1. Gram Stain clear or with Gram Negative diplococci
          1. Ceftriaxone 1 gram IV q24 hours or
          2. Cefotaxime 1 gram IV q8 hours or
          3. Ceftizoxime 1 gram IV q8 hours
       2. Gram Stain with Gram Positive Cocci
          1. Vancomycin 15-20 mg/kg IV q8-12 hours
       3. Gram Stain with Gram Negative Bacilli
          1. Cefepime 2 grams q8 hours IV or
          2. Meropenem 1 gram q8 hours IV
    2. Acute monoarticular without STD risk
       1. Gram Stain Negative (2 drug regimen)
          1. Drug 1: Vancomycin 15-20 mg/kg IV q8-12 hours
          2. Drug 2: Choose one
             1. Ceftriaxone 1 gram IV q24 hours or
             2. Cefepime 2 grams IV q8 hours
             3. Alternative: Ciprofloxacin 400 mg q12 hours or Levofloxacin 750 mg IV q24 hours
       2. Gram Stain with Gram Positive Cocci
          1. Vancomycin 15-20 mg/kg IV q8-12 hours
       3. Gram Stain with Gram Negative Bacilli
          1. Cefepime 2 grams q8 hours IV or
          2. Meropenem 1 gram q8 hours iv
    3. Polyarticular Arthritis
       1. Ceftriaxone 1 gram IV q24 hours
17. Management: Iatrogenic Infection (Joint Injection or prosthesis)
    1. Empiric therapy before culture results
       1. Option 1 (2 drug regimen)
          1. Drug 1: Vancomycin
          2. Drug 2: Ciprofloxacin, Aztreonam, or Gentamycin
       2. Option 2 (2 drug regimen)
          1. Drug 1
             1. Ciprofloxacin 750 PO bid or
             2. Ofloxacin 200 mg PO tid
          2. Drug 2: Rifampin 900 mg PO qd
    2. Ciprofloxacin and Rifampin sensitive by culture
       1. Option 1 (2 drug regimen)
          1. Drug 1: Ciprofloxacin or Ofloxacin
          2. Drug 2: Rifampin 900 mg PO qd
       2. Option 2 (2 drug regimen)
          1. Drug 1: Oxacillin 2 grams IV every 4 hours
          2. Drug 2: Rifampin 900 mg PO qd
    3. Ciprofloxacin or Rifampin resistance by culture
       1. Vancomycin and
       2. Rifampin (if sensitive)
18. Management: Antibiotic Course
    1. Nongonococcal bacterial infection
       1. Parenteral antibiotics for 2 to 4 weeks
       2. Oral antibiotics for 2 to 4 weeks
    2. See Gonococcal Arthritis
    3. See Tuberculous Arthritis
19. Prognosis
    1. Early joint drainage and antibiotics
       1. Good prognosis
    2. Delayed management >24 hours
       1. Risk of joint arthrosis, fibrosis and osteonecrosis
20. References
    1. Klippel (1997) Primer Rheumatic Diseases, p. 196-200
    2. Gilbert (2012) Sanford Guide to Antimicrobials
    3. Merenstein (1994) Handbook Pediatrics, Lange, p.710-2
    4. Carpenter (2011) Acad Emerg Med 18(8):781-96
    5. Stimmler (1996) Postgrad Med 99(4):127-39
    6. Kallio (1997) Pediatr Infect Dis 16:411-2