[Lumbar interapophyseal septic arthritis. Apropos of 3 cases].

Septic arthritis of spinal apophyseal joint, seldom described, mainly concern the lumbar spine. We report three cases. Inflammatory lesions of the paravertebral soft tissues were associated in each case; an epidural abscess was present twice. Our three cases were due to Staphylococcus aureus. The initial clinical features were consistent with a spondylodiscitis. Imaging led to the correct diagnosis in all cases. According to our observations and several others of the literature: facet joint lesions are visible too late on plain films. Bone scintigraphy is sensitive, but not specific. CT scan and MRI are the most contributive investigations. A pathologic aspect of the paravertebral soft tissues is visible less than one week after the beginning of the symptoms on CT scan and MRI. Lesions of the facet joint are detectable as soon as the first week on MRI, and after 15 days of clinical course on CT scan. Epidural abscess, when present, is best shown by MRI as early as the first week. CT scan can guide percutaneous needle biopsies of the paravertebral abscesses or of the concerned facet joint.