Presence of Modic type 1 change increases risk of postoperative pyogenic discitis following decompression surgery for lumbar canal stenosis

Study Design Multicenter retrospective study. Background Postoperative surgical site infection is one of the most serious complications following spine surgery. Previous studies do not appear to have investigated pyogenic discitis following lumbar laminectomy without discectomy. This study aimed to identify risk factors for postoperative pyogenic discitis following lumbar decompression surgery. Methods We examined data from 2721 patients undergoing lumbar laminectomy without discectomy in five hospitals from April 2007 to March 2012. Patients who developed postoperative discitis following laminectomy (Group D) and a 4:1 matched cohort (Group C) were included. Fisher's exact test was used to determine risk factors, with values of p < 0.05 considered statistically significant. Results The cumulative incidence of postoperative discitis was 0.29% (8/2721 patients). All patients in Group D were male, with a mean age of 71.6 ± 7.2 years. Postoperative discitis was at L1/2 in 1 patient, at L3/4 in 3 patients, and at L4/5 in 4 patients. Except for 1 patient with discitis at L1/2, every patient developed discitis at the level of decompression. The associated pathogens were methicillin-resistant Staphylococcus aureus (n = 3, 37.5%), methicillin-susceptible Staphylococcus epidermidis (n = 1, 12.5%), methicillin-sensitive S. aureus (n = 1, 12.5%), and unknown (n = 3, 37.5%). In the analysis of risk factors for postoperative discitis, Group D showed a significantly lower ratio of patients who underwent surgery in the winter and a significantly higher ratio of patients who had Modic type 1 in the lumbar vertebrae compared to Group C. Conclusions Although further prospective studies, in which other preoperative modalities are used for the evaluation, is needed, our data suggest the presence of Modic type 1 as a risk factor for discitis following laminectomy. Latent pyogenic discitis should be carefully ruled out in patients with Modic type 1. If lumbar laminectomy is performed for such patients, more careful observation is necessary to prevent the development of postoperative discitis.