Risk Factors for the Development of Delayed Infection Following Posterior Spinal Fusion and Instrumentation for AIS

Methods: In this retrospective, IRB approved study, 1046 patients were identified whose index PSFI for AIS was between Jan 1988 and Dec 2003. Those patients who required treatment for delayed infections were identified (group 1).A random selection of patients who did not develop delayed infections (group 2) was made in a ratio of 3:1 (no infection:infection). The two groups were compared using statistical methods.

Results: There were no differences between groups with respect to age, gender, or ethnicity. Parameters which were associated with infection (group 1) included: a significant past medical history, surgeon, less surgical time, the sterile prep wash of the patient, harvesting of the left iliac crest (compared to the right), a more distal fusion level (distal end vertebra L1-L4, 82.9% infection group, vs. 64.9% no infection group), the use of two crosslinks (77.1 vs. 58.2%), incidence of drain usage (38.4% vs. 86.7%) and more return of cell saver (311.0 vs 229.7 cc). Most patients had the same antibiotic regimen pre and post-operatively. Factors which were not associated with delayed infection included: BMI, the number of anchor points utilized, use of allograft bone, and the total number of levels instrumented.

Conclusions: Several factors were identified which are associated with the development of delayed infection. The occurrence of a delayed infection is most likely multi-factorial, including surgeon variability, surgical technique, and number of crosslinks. Postoperative use of a drain may be important to avoid delayed infection.