Septic Arthritis Pamela Gregory-Fernandez, PA-C SVCMC PA Education Program

Definition  Inflammation of a synovial membrane with purulent effusion into the joint capsule, often due to bacterial infection

Synonyms  Bacterial, suppurative, purulent or infectious arthritis, gonococcal or nongonococcal

A Big Problem  Despite advances in diagnostic studies, powerful antibiotics, and early drainage, significant joint destruction commonly occurs  Why ? Lack of clinical suspicion Delay in definitive diagnostic needle aspiration Failure to adequately drain the joint

Frequency  2-10 cases per 100,000 in the general population  cases per 100,000 in patients with immunological disorders or deficiencies, and joint replacements  Gonococcal: women 3x > men

Etiology  Staph aureus  Streptococci  In all age groups, 80% due to gram-positive aerobes, 20% due to gram-negative anaerobes  Neonates and infants < 6mos S aureus and gram- negative anaerobes Incidence of H. influenzae has decreased due to the vaccine

Pathophysiology  Adults Knee % Hip % Infants and young children Hip 95 %

Infection Sources  Trauma: direct  Hematogenous: IV drug injection  Osteomyelitis adjacent to joint capsule  Soft tissue infections: cellulitis, abscess, bursitis, tenosynovitis

Clinical Presentation: “red, hot, painful joint”  Fever  Erythema  Edema  Heat  Pain  Markedly decreased passive and active ROM

Age Related Presentation  Young sexually active pts: + fever, tenosynovitis, migratory polyarthralgia and dermatitis ( papular rash over trunk and distal extremity extensor surfaces that may turn hemorrhagic ) = Suspect N gonorrheae  IVDU = Pseudomonas  Infants and young children = difficult

Pediatric Presentation  Fever, decreased appetite and irritability without obvious joint involvement is common  Differentiation from transient synovitis important: 4 independent variables History of fever Non-weight-bearing ESR > 40mm/h WBC > 12,000/uL

Diagnosis  Needle aspiration, open drainage and lavage (arthroscopically or arthrotomy) Contraindications to arthrocentesis: 1. avoid aspirating from an area that has overlying soft tissue infection 2. Bleeding disorders 3. Anticoagulation therapy

Lab Studies  CBC with diff: leukocytosis and left shift  ESR: monitor treatment  CRP: monitor treatment  Blood cultures: may be + in 50% S aureus  Urethral, cervical, pharyngeal and rectal swabs: N gonorrheae  Synovial fluid analysis: Gram stain, culture, cell count, and crystal analysis

 Synovial Fluid Classification (Modified from Schumacher HR. Pathologic Findings in Rheumatoid Arthritis) Quality  Reference Range  Noninflammatory  Inflammatory  Septic  Volume, mL  <3.5  >3.5  Viscosity  High  Low  Variable  Color  Clear  Straw-yellow  Yellow  Variable  Clarity  Transparent  Translucent  Opaque  WBC,  L  200-2,000  2,000-75,000  <200  Often >100,000  PMN, %  <25%  >50%  >75%  Culture result  Negative  Often positive*  Mucin clot  Firm  Friable  Glucose  ~Blood  Decreased  Very decreased  *Note: Synovial fluid culture results are positive in 85-95% of nongonococcal arthritis cases and approximately 25% in gonococcal arthritis cases.