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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.
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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 • 30-70 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 40-50 % • Hip 20-25 % • 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 • >3.5 • >3.5 • Viscosity • High • High • Low • Variable • Color • Clear • Straw-yellow • Yellow • Variable • Clarity • Transparent • Transparent • Translucent • Opaque • WBC, mL • 200-2,000 • 2,000-75,000 • <200 • Often >100,000 • PMN, % • <25% • <25% • >50% • >75% • Culture result • Negative • Negative • Negative • Often positive* • Mucin clot • Firm • Firm • Friable • Friable • Glucose • ~Blood • ~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.