Clinical prediction algorithms are used to differentiate
transient synovitis from septic arthritis. These algorithms typically
include the erythrocyte sedimentation rate (ESR), although in clinical practice
measurement of the C-reactive protein (CRP) has largely replaced
the ESR. We evaluated the use of CRP in a predictive algorithm. The records of 311 children with an effusion of the hip, which
was confirmed on ultrasound, were reviewed (mean age 5.3 years (0.2
to 15.1)). Of these, 269 resolved without intervention and without
long-term sequelae and were considered to have had transient synovitis.
The remaining 42 underwent arthrotomy because of suspicion of septic
arthritis. Infection was confirmed in 29 (18 had micro-organisms
isolated and 11 had a high synovial fluid white cell count). In
the remaining 13 no evidence of infection was found and they were
also considered to have had transient synovitis. In total 29 hips
were categorised as septic arthritis and 282 as transient synovitis.
The temperature, weight-bearing status, peripheral white blood cell
count and CRP was reviewed in each patient. A CRP >
20 mg/l was the strongest independent risk factor for
septic arthritis (odds ratio 81.9, p <
0.001). A multivariable
prediction model revealed that only two determinants (weight-bearing
status and CRP >
20 mg/l) were independent in differentiating septic
arthritis from transient synovitis. Individuals with neither predictor
had a <
1% probability of septic arthritis, but those with both
had a 74% probability of septic arthritis. A two-variable algorithm
can therefore quantify the risk of septic arthritis, and is an excellent
negative predictor.
A careful study of children with transient synovitis of the hip has failed to establish any connection with infection by staphylococci or streptococci, with allergy, with viral infection and with trauma.
1. Transient synovitis is an acute, and at times exudative, condition of the synovial membrane. 2. There is no particular association with injury or with upper respiratory infection. 3. The course is short and benign with complete resolution. The occasional hip with chronic or recurrent symptoms can be distinguished from Legg-Perthes' disease by the shorter history, normal radiographs and the complete resolution. 4. There is no evidence that transient synovitis leads to avascular changes in the femoral head.
