Risk of infection following posterior instrumented lumbar fusion for degenerative spine disease in 817 consecutive cases.

OBJECT: Posterior lumbar spinal fusion for degenerative spine disease is a common procedure, and its use is increasing annually. The rate of infection, as well as the factors associated with an increased risk of infection, remains unclear for this patient population. A better understanding of these features may help guide treatment strategies aimed at minimizing infection for this relatively common procedure. The authors' goals were therefore to ascertain the incidence of postoperative spinal infections and identify factors associated with postoperative spinal infections.

METHODS: Data obtained in adult patients who underwent instrumented posterior lumbar fusion for degenerative spine disease between 1993 and 2010 were retrospectively reviewed. Stepwise multivariate proportional hazards regression analysis was used to identify factors associated with infection. Variables with p < 0.05 were considered statistically significant.

RESULTS: During the study period, 817 consecutive patients underwent lumbar fusion for degenerative spine disease, and 37 patients (4.5%) developed postoperative spine infection at a median of 0.6 months (IQR 0.3-0.9). The factors independently associated with an increased risk of infection were increasing age (RR 1.004 [95% CI 1.001-1.009], p = 0.049), diabetes (RR 5.583 [95% CI 1.322-19.737], p = 0.02), obesity (RR 6.216 [95% CI 1.832-9.338], p = 0.005), previous spine surgery (RR 2.994 [95% CI 1.263-9.346], p = 0.009), and increasing duration of hospital stay (RR 1.155 [95% CI 1.076-1.230], p = 0.003). Of the 37 patients in whom infection developed, 21 (57%) required operative intervention but only 3 (8%) required instrumentation removal as part of their infection management.

CONCLUSIONS: This study identifies that several factors--older age, diabetes, obesity, prior spine surgery, and length of hospital stay--were each independently associated with an increased risk of developing infection among patients undergoing instrumented lumbar fusion for degenerative spine disease. The overwhelming majority of these patients were treated effectively without hardware removal.