[Spondylodiscitis after operation for lumbar disc herniation]

Postoperative spondylodiscitis (POD) is a rare but severe complication of lumbar disc surgery. There were five patients with POD among 875 patients undergoing surgery for herniated lumbar discs, in the last 16 years. For detecting risk factor of discitis, a POD group of 5 patients was matched to a control group of 870 patients with respect to sex, age, disc type and operation. In five patients with POD follow-up evaluation of clinical symptoms, laboratory data were obtained, and magnetic resonance (MR) imaging was performed. A significant difference between the POD group and the control group was confirmed in sex, operation time and the volume of bleeding during operation. However, there was no significant difference confirmed due to age, disc type, disc level and operative procedure. In the case of males or prolonged operation time or increase of the volume of bleeding, POD may be more frequently observed. All five patients had a period of pain relief after their operations and then reported increasing low back pain with no focal signs. At diagnosis of POD all patients had an erythrocyte sedimentation rate (ESR) greater than 30 per hour and C-reactive protein (CRP) higher than 2.5. After treatment by antibiotics, low back pain gradually receded along with decrease of ESR and CRP. About 40 days later, these patients were almost free of back pain and ESR and CRP were within normal range. MRT1-weighted image during the acute phase demonstrated remarkably decreased signal intensity with loss of distinction between vertebral body and disc space. T2-weighted image showed increased signal intensity in the adjacent vertebral bodies and end-plates. Gadolinium-enhanced T1-weighted image had homogenous enhancement of vertebral body and disc space. During the subacute phase, however, T1-weighted image demonstrated moderately decreased signal intensity noted in the posteroinferior portion of the L5 vertebral body and the narrowed L5/S1 disc space. T2-weighted image showed iso signal intensity in L5 and S1 vertebral bodies. Gadolinium-enhanced T1-weighted image had mild homogenous enhancement in the posteroinferior portion of the L5 vertebral body. Three months after treatment of POD, there was major signal change in neither T1 nor T2 weighted images, though T2 showed subtle abnormalities with decreased signal intensity adjacent to the L5/S1 disc space.