septic arthritis vs. transient synovitis in kids

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


Submitted by S. Lee.


Reference(s): kocher article, picture