Risk factors for the development of delayed infections following posterior spinal fusion and instrumentation in adolescent idiopathic scoliosis patients

Study Design. Retrospective comparison study of patients who had a delayed infection following a posterior spinal fusion and instrumentation (PSFI) for adolescent idiopathic scoliosis (AIS). Objective. To define risk factors for the development of delayed infections following PSFI for AIS by comparing those patients who developed this complication to a randomly selected group of patients who did not. Summary of Background Data. Despite studies reporting the incidence and treatment of delayed infection following PSFI for AIS, there are no studies analyzing risk factors for its occurrence. Methods. All patients who required treatment for delayed infections following PSFI for AIS were identified ( infection group, n = 36). A random selection of patients who did not develop a delayed infection ( no infection, n = 90) was made in a ratio of 3: 1 ( no infection/infection). The 2 groups were compared using statistical methods. Results. Parameters associated with the infection group included: presence of a significant medical history, surgeon, less surgical time, a more distal fusion level (16% infection rate with a thoracic LIV vs. 33% infection rate with a lumbar LIV), not using postoperative drains, and increased drainage when drains were used. Other factors associated with infection were use of a blood transfusion and when increasing units of transfusion were used. Multivariate logistic regression analysis identified 3 factors that remained statistically significant: 1) significant medical history, 2) receiving a blood transfusion, and 3) not using a postoperative drain. Factors that were not associated with delayed infection included body mass index, the number of anchor points used, use of allograft bone, and the total number of levels instrumented and antibiotic regimen. Conclusion. The occurrence of a delayed infection is most likely multifactorial and is related to a positive past medical history and the use of blood transfusions. Postoperative use of a drain may be important to avoid delayed infection.