septic arthritis vs. transient synovitis in kids

3 Nov

repost of an old entry, but came up again recently, worth a review:

HOW CAN WE TELL THE DIFFERENCE?
–lots of overlap in signs/symptoms
–one article came up with a decent decision rule

J Bone Joint Surg Am. 1999 Dec;81(12):1662-70.
–looked at 282 cases, excluded 114 atypical patients (e.g. immunocompromised), leaving 168
–38 had “true” septic arthritis
septic arthritis defined by positive culture or joint WBC >= 50,000 cells/mm3

–four things they decided on that might differentiate:

  • history of fever
  • non-weight-bearing
  • erythrocyte sedimentation rate (ESR) >= 40 mm/hr
  • serum WBC > 12,000 cells/mm3

–predicted probability of septic arthritis using these four predictors:

  • < 0.2 percent for zero predictors
  • 3.0 percent for one predictor
  • 40.0 percent for two predictors
  • 93.1 percent for three predictors
  • 99.6 percent for four predictors

BOTTOM LINE:
–septic arthritis is bad, transient synovitis not so bad
–hard to tell sometimes, signs/symptoms are often similar
–useful: history of fever, non-weight bearing, ESR>40, WBC>12k
–if none of the above: unlikely septic arthritis
–more of the above: worry a bit more

Reference(s): kocher article, picture

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