A Rare Cause of Low Back Pain: A Challenging Diagnosis

One of the rarest causes of low back pain is septic arthritis of a lumbar facet joint. We report the case of a 92-year-old diabetic woman with a history of four days of back pain, dysuria, and fever. Due to a sudden worsening of lumbar pain, she went to the emergency department. Physical exam revealed pain with pressure over the D12 vertebral apophyses and the lower-left paraspinal musculature. Laboratory data showed a normochromic normocytic anemia with a hemoglobin of 9.3 g/dL, white cell count of 14.61x10e3/µL (83.1% neutrophils), serum creatinine 1.46 mg/dL and C-reactive protein of 32.11 mg/dL. In urinalysis, nitrites and leukocyturia were identified. CT scan showed an acute D12 fracture and fat stranding at L5, with no irregularities in the discs or in other lumbar spaces. Escherichia coli was isolated in blood culture. Lumbar MRI confirmed the diagnosis of septic arthritis of an L5-S1 facet joint and L5 vertebrae osteomyelitis. The patient was successfully treated with intravenous ceftriaxone for eight weeks. As far as we know, this is the second report of septic arthritis of the facet joint caused by Escherichia coli.