Acute haematogenous septic arthritis of a lumbar facet joint in an otherwise healthy adolescent.

Facet joint septic arthritis is a rare cause of spinal infection in children with only four cases reported. The transmission pathway is believed to be haematogenous in 72% of cases. The authors present the case of a 13-year-old boy hospitalised for acute lumbosciatalgia, limp and fever, with pain upon palpation of the paravertebral muscles, a positive Laségue signal and elevated serum inflammatory markers. The initial lumbar computerised tomography (TC) scan revealed no abnormalities in the interapophyseal joints. After improving on treatment with analgesics and antibiotics, he was readmitted one month later due to clinical deterioration, and septic arthritis of left facet joint L3-L4 was confirmed by magnetic resonance imaging (MRI). The patient experienced a full recovery after treatment with systemic antibiotics (cefotaxime-cloxacilin) and rehabilitation. A high index of suspicion is necessary to diagnose this localization as a manifestation of lumbosciatalgia and/or limp in children. CT-scan or, preferably, MRI is mandatory to confirm this diagnosis.