Magnetic Resonance Imaging Patterns of Post-Operative Spinal Infection : Relationship between the Clinical Onset of Infection and the Infection Site

Objective : To investigate the magnetic resonance imaging (MRI) findings and the patterns of postoperative spinal infection according to the passage of time. Methods : Institutional review board approval was obtained, and informed consent was not obtained for the retrospective review of patients' medical records. A total of 43 patients (27 men and 16 women; mean age, 64) diagnosed with postoperative spinal infection were included in this study. We retrospectively reviewed the MRI findings and the medical records and categorized the infection sites based on MRI, i.e., anterior, posterior, and both parts. The duration of the clinical onset from surgery was divided, i.e., acute (${\leq}2weeks$), subacute (2-4 weeks), and late (>4 weeks). Results : Postoperative spinal infection was involved in the posterior part in 31 (72%), anterior part in two (4.7%), and both parts in 10 patients (23.3%). Abscess or phlegmon in the back muscles and laminectomy site were the most common MRI findings. The number of patients with acute, subacute, and late clinical onset were 35, two, and six, respectively (mean, 33.4 days; range, 1-730 days). The mean duration of the clinical onset was 12 days in the posterior part, 15.2 days in both parts, and 456.5 days in the anterior part. Conclusion : Postoperative spinal infection usually occurred within four weeks in the posterior part and over time the infection was considered to spread into the anterior part. For the evaluation of postoperative spinal infection, the posterior surgical field was more important than the vertebral body or the disc space on MRI.