Septic Arthritis

Septic Arthritis Epidemiology Gonococcal is more common in women who develop arthritis in the perimenstrual period. Risk Factors Aged more than 80 Diabetes mellitus RA and other joint disease Prosthetic joint Recent joint surgery Skin infections Cutaneous ulcers IV drug use Alcoholism Previous intra-articular corticosteroid injection Immunocompromise Causes S. aureus Most common Streptococci Other staphylococcus species Neisseria gonorrhoeae Hemophilus influenza in children Other gram-negative organisms in elderly Key info A medical emergency that requires a risk of prolonged morbidity and mortality Must be excluded in all cases of acute monoarthritic Gonococcal septic arthritis does not have systemic or cutaneous features in 50% of cases should be considered and ruled out in all sexually active patients in young adults -> common cause of non-traumatic acute monoarthritis Clinical Features usually polyarticular pyrexia tenosynovitis pustular rash of the extremities painful joint unable to bear weight erythematous swollen joint movement difficulty and ROM fever and chills malaise men usually develop urethritis as dysuria morning discharge women usually asymptomatic Investigations Bloods and blood culture FBCs Inflammatory markers Urate levels if suspected gout Monitoring of urinary output Arthrocentesis/Joint aspiration Most useful way of diagnosis -> gold standard To be done sterile Can be done at the bedside May need some radiological guidance e.g. hips and sacroiliac joints All samples should be sent in: Purple top tube: microscopy and cell count Yellow top jar: crystal examination Aerobic and anaerobic cultures 1 to 2 ml of fluid is enough for each bottle Synovial fluid analysis Measure Normal Noninflammatory Inflammatory Septic Haemorrhagic Volume, mL (knee) <3.5 Often >3.5 Often >3.5 Often >3.5 Usually, >3.5 Clarity Transparent Transparent Translucentopaque Opaque Bloody Colour Clear Yellow Yellow to opalescent Yellow to green Red Viscosity High High Low Variable Variable WBC, per mm3 <200 200-2,000 2,000-100,000 15,000->100,000* 200-2,000 PMNs, percent <25 <25 50-75 Culture Negative Total protein, g/dL 1-2 Glucose, mg/dL Nearly equal to blood Negative Negative Often positive Negative 1-3 3-5 3-5 4-6 Nearly equal to blood >25, lower than blood <25, much lower than blood Nearly equal to blood Skin wound swaps, sputum, throat swap or urine May be useful for finding the source of infection Plain x-ray of affected joint AP and LP No real valve in diagnosis of SA? Exclude fractures Findings: Soft tissue swelling Capsular distension Joint space widening due to effusion Osteopenia Later joint space narrowing Cartilage loss Bone erosions CT or MRI Rarely performed Management Empirical treatment IV antibiotics Flucloxacillin Cephalexin is another option Involve ID registrar or consultant Analgesia IV antibiotics for 2 weeks and then oral for 4-6weeks Initial immobilisation then early physiotherapy to prevent stiffness and muscle wasting Response is monitored clinical and with ESR and CRP Surgical irrigation and debridement – wash out Contact orthopaedic surgery Done in theatre Irreversible cartilage damage can happen within 8 hours of infection If infection is within a prosthetic joint Washout is still required But revision surgery is required Acutely or staged DDx Osteoarthritis Cystal arthropathies RA Reactive arthritis Lyme disease Complications Severe joint destruction Most common Cartilage loss Chronic pain Reduced movement Osteomyelitis Septic shock Systemic sepsis Bacteria Endocarditis Osteonecrosis Leg length discrepancies