Septic arthritis of lumbar facet joints. A review of six cases.

Hematogenous infection of the facet joints by pyogenic organisms is exceedingly rare. We report six cases of lumbar facet joint septic arthritis due to hematogenous spread of a pyogenic organism. A review of the literature identified ten anecdotal reports of similar cases. An analysis of these 16 cases showed that the diagnosis was based mainly on imaging study findings and that clinical data failed to discriminate between facet joint septic arthritis and infectious discitis. Increased uptake on the radionuclide bone scan was an early finding and the pattern of uptake was different from that seen in discitis. Computed tomography was the investigation that best delineated the facet joint lesions. Magnetic resonance imaging of the lumbar spine was superior over computed tomography in demonstrating spread of the infection to the epidural space and/or soft tissues and in some instances demonstrated enhancement of the infected facet joint on T1 images after gadolinium injection. Aspiration of the facet joint under fluoroscopic guidance was required only when blood cultures were negative or when the diagnosis of the septic nature of the arthritis was in doubt. Blood cultures yielded a Staphylococcus aureus in the six cases in our series. Appropriate antimicrobial therapy was successful in most cases. In our series, four of the six patients had posterior epiduritis, pyomyositis, or an abscess in the paraspinal muscles or psoas muscle, suggesting that some epidural infections or psoas muscle abscesses believed heretofore to be primary may in fact be complications of facet joint septic arthritis. Facet joint septic arthritis is a new aspect of pyogenic spinal infections that deserves to be considered in patients with febrile spinal syndromes not explained by discitis.