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Several independent risk factors for septic knee arthritis identified
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Compared with Lyme disease, septic arthritis was identified in pediatric patients younger than 2 years who have pain with short arc motion, C-reactive protein levels of greater than 4 mg/L and a patient-reported history of fever, according to results.
Researchers compared historical, clinical and laboratory data among patients younger than 18 years with knee effusions who underwent arthrocentesis and were diagnosed with either septic arthritis or Lyme disease.
Results showed, of 189 patients identified, 23 patients had culture-positive septic arthritis; 26 patients had culture-negative septic arthritis; and 140 patients had Lyme disease. Researchers found 33% of patients diagnosed with Lyme disease underwent surgical incision and drainage based on a presumed diagnosis of septic arthritis. Mean synovial white blood-cell count, serum white blood-cell count, erythrocyte sedimentation rate and C-reaction protein (CRP) levels differed significantly between patients with Lyme arthritis who underwent incision and drainage vs. patients who did not undergo a surgical procedure.
According to results of a multivariate binary logistic regression, independent predictive factors for septic arthritis included pain with short arc motion, history of fever reported by patients or by a family member, CRP level of greater than 4 mg/L and age younger than 2 years. Researchers found a risk of septic arthritis of 2% with none of these factors, 18% with one factor, 45% with two factors, 84% with three factors and 100% with all four factors.
“Our predictive model for differentiating septic arthritis from Lyme disease of the knee demonstrates clear direction for patients on either end of the model. Those with all four risk factors (pain with short arc knee motion, CRP [greater than] 4, history of fever and age [younger than] 2) should clearly be treated as septic arthritis with urgent surgery, while those with zero risk factors can be safely observed,” Wudbhav N. Sankar, MD, associate professor of orthopedic surgery at the Perelman School of Medicine at the University of Pennsylvania, told Healio.com/orthopedics. “In between, the risk of having septic arthritis increased with each additional risk factor.” – by Casey Tingle
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