Transient synovitis of the hip: which investigations are truly useful?

QUESTIONS UNDER STUDY/PRINCIPLES To assess the usefulness of several laboratory and radiological investigations for the limping child with suspected transient synovitis of the hip. METHODS The medical records of children admitted at our children's hospital for nontraumatic hip pain between 1999 and 2007 were retrospectively reviewed. During the study period, all children without a definite diagnosis after routine investigations in the emergency department were admitted and a specific work-up including antinuclear antibodies titre, rheumatoid factor, antistreptolysin O titre, Lyme disease serology and hip ultrasonography were obtained. Children were systematically re-evaluated 6 weeks after hospital discharge, with a clinical examination and radiological hip views. Patients were diagnosed with transient synovitis of the hip if an ultrasound-confirmed hip effusion was present at time of admission, complete resolution of symptoms occurred without any specific treatment, and no other pathology of the hip was identified during follow-up. RESULTS A total of 417 cases without definite diagnosis were admitted and were submitted to a specific work-up. Transient synovitis of the hip was subsequently diagnosed in 383 patients, septic arthritis in 1 patient, and Lyme arthritis in 1 patient. Thirty-two patients remained without diagnosis. No rheumatological condition was found. CONCLUSION Our results suggest that most investigations performed during the initial work-up in patients suspected transient synovitis of the hip are unnecessary and should routinely include only white blood cell count, C-reactive protein, erythrocyte sedimentation rate, and hip radiography and ultrasonography. No further investigations are necessary during follow-up for transient synovitis of the hip in asymptomatic children.