Septic arthritis

Background

• Def: inflammation of a synovial membrane with purulent effusion into the joint capsule
• usually affects monoarticular joints (the knee is most commonly affected in adults and the hip in children)
• Relatively rare disease however because it can quickly destroy the joint or lead to osteomyelitis, fibrous ankylosis, sepsis, or even death it is important to catch and treat promptly
• Frequency is ~20,000 cases in USA/year (may be higher in pts with immunologic disorders (RA, SLE))
• M>F predominance, usually in patients >65 years
• Etiology is usually bacterial, divided into gonococcal or nongonococcal groups
• staph and strep are most common nongonococcal causes
• consider different organisms in children, IV drug users, and those with prosthetic joints

Diagnosis

• may be difficult to diagnose in early stages
• patient typically presents with fever and a warm, red, painful, swollen joint with decreased range of motion even passively
• confirm diagnosis with work up

Infected fluid characteristics

1. large amount (>3.5 mL)
2. turbid in appearance
3. decreased viscosity
4. 15,000->200,000 leukocytes/cubic cm (15-200 x 10^9 per L)
   1. Likelyhood ratios:
      1. 0-25,000 = 0.33
      2. 25,000-50,000 = 1.06
      3. 50,000-100,000 = 3.59
      4. >100,000 = infinity
5. 50-100% PMNs
6. Poor mucin clot
7. glucose >40mg/100mL less than plasma glucose
8. Positive culture

Work-Up

1. CBC
2. ESR
3. Blood Cultures
4. Gonorrhea culture (urethral/cervical/pharyngeal/rectal)
5. Arthrocentesis with synovial fluid analysis
6. Plain films (often normal but may show widening of joint space or evidence of osteomyelitis)
7. Ultrasound (can show joint effusion, extent of disease, and may help differentiate from other conditions)

DDx

1. toxic synovitis
2. abscess
3. cellulitis
4. primary rheumatologic disorder (i.e. vasculitis)
5. iatrogenic
6. reactive arthritis (post infectious)

Gonococcal Arthritis

Healthy, young sexually active adults

Women > men

Suppurative monoarthritis (may be preceded by polyarthralgias)

Knee, wrist, ankle

Arthritis-Dermatitis Syndrome

Diagnosis

1. Triad: dermatitis, tenosynovitis, migratory polyarthritis (hematogenous spread of bacteria and immune complexes)
2. Skin lesions: scattered small painless erythematous macules or petechiae-->pustular -->necrotic lesions
3. Transient painful extensor tenosynovitis (writs, hands, ankles)
4. Asymmtric polyarthralgia of extremity joints
5. Diagnosis Cx everything - jt, mucosal surfaces, lesions

Treatment

CTX 1gIV qd OR

Cefotax 1g q8

Empirically treat Chlamydia

Nongonococcal Arthritis

Background

Fulminant presentation (abrupt, swelling, toxicity and fever) unless elderly

1. Hematogenous
2. Contiguous
3. Direct traumatic implantation
4. Postop

Causes

1. Bacterial
2. Mycobacterial
3. Spirochete (lyme, syphilis)
4. Fungal
5. Viral (HIV, Hep B, Rubella, etc)
6. Postinfectious

Diagnosis

1. Synovial fluid aspiration
2. Cx - if only one test, use BCx bottles (may enhance yield)
3. Grm stain - 80% positive in gram-positive infxn; less sens in gram-negative
4. Cell count with dif - >50,000-150,000; PMN > 90%

Treatment

1. PCN-ase resistant synthetic PCN:
   1. Nafcillin 1-2g
   2. Cefazolin 1-2g

AND 3rd gen ceph

OR

Vanc^

^new evidence suggests significantly increased rate of MRSA septic arthritis

^^cell counts are as low as 20,000 in MRSA Cx + synovial fluid

Treatment

1. drainage of the joint
2. IV Antibiotics
3. generally Oxacillin or Nafcillin with a cephalosporin (ceftriaxone, feotaxme, ceftizoxime) will cover
4. add vancomycin if you suspect MRSA
5. in IVDA patients use IV aminoglycoside + antipseudomonal cephalosporin
6. patients with prosthetic joints are at higher risk of MRSA, MRSE, Enterobacteriaceae, and Pseudomonas
7. consider gonococcal infection in young sexually active patients (treat with ceftriaxone)
8. Open drainage and lavage in the OR

Disposition

• All patients should be admitted with Ortho consult and continued on IV antibiotics

See Also

• Arthrocentesis
• Monoarticular Arthritis
• Septic Arthritis (Hip)
• Septic Arthritis (Peds)

Source

http://emprocedures.com/arthrocentesis/analysis.htmEmedicine