Precautions Against Infection Following Posterior Spinal Fusion Based on Types of Infection and Risk Factors

Study D Design: This is a retrospective preparative study and prospective studyObjective: We instituted and verified the precautions against postoperative spinal infection.Summary o of t the L Literature R Review: Postoperative infection comes from contamination during the operation and various strategies have been recommended to prevent it.Materials a and M Methods: 583 cases that underwent instrumented posterior spinal fusion during two years (group I), were reviewed to discover the risk factors, and intraoperative cultures were done to detect the contamination routes and the causative microorganisms for the next 4 months.Six precautions, based on the results, were instituted.We analyzed 354 cases that underwent operation in the following year (group II) using the precautions.Results: Twenty cases (3.4%) were infected in group I and the types of infection were superficial wound infection (4 cases), deep wound infection (4 cases), osteomyelitis around the interbody space (7 cases), osteomyelitis around the pedicle screws (4 cases) and a combination of wound infection and osteomyelitis around the pedicle screws (1 case).Infections happened more frequently in the cases of interbody fusion (p=0.034),revision (p=0.087) and those done in the summer season (p=0.025).S. epidermidis, as the causative bacteria, was cultured from both the operation environments and wounds.Six precautions based on the preliminary results were instituted as follows; irrigation method reformation, delayed opening of instruments, turning-off local air conditioners, changing of gowns before instrumentation, local bone irrigation and limited indications for interbody fusion.After implementation, two cases (0.6%) of infection developed in group II (p=0.002,odds ratio=0.160;95% confidence interval = 0.037 to 0.688).Conclusion: Wounds, grafted bones or instruments can be contaminated under longer-time exposure to operating room air and so produce interbody or pedicle osteomyelitis without wound infection.The precautions were effective to decrease the postoperative infection rates following posterior spinal fusion. Key W Words: Spinal fusion, Routes of contamination, Prevention of infection* Statistically significant (confidence interval 10% to reduce beta error intentionally)