Diagnostic performance of suction drainage fluid culture for acute surgical site infection after aseptic instrumented spine surgery: a retrospective analysis of 363 cases.

Purpose: Analyze the diagnostic performance of suction drainage fluid culture for acute surgical site infection, which has not been specifically reported in spine surgery patients.
Method: This was a retrospective single-center observational study including data from 363 patients who underwent aseptic instrumented spine surgery between 2015 and 2017. A suction drain was inserted in all cases. Data analyzed were patient age, gender, ASA score, indication for surgery (degenerative disease, tumor, trauma), spine level (cervical, thoracic, lumbar), procedure performed and spine level, operative time, body temperature, postoperative C-reactive protein time-curve, clinical aspect of surgical scar, bacteriology results of suction drainage fluid, and in case of revision surgery, lavage fluid. Major criteria for periprosthetic infection proposed by the Musculoskeletal Infection Society (MSIS) were accepted as the gold standard for the diagnosis of acute surgical site infection.
Results: The overall rate of surgical site infection was 6.9% (5.76% for 1- or 2-level fusion, 5.81% for 3- or 4-level fusion, and 15.6% for 5-level fusion and above). The suction drain was withdrawn on the second postoperative day in 44.1% of cases and the third day in 39.1%. The sensitivity of suction drainage fluid culture for the diagnosis of surgical site infection was 20% [95%CI 6.8-40.7%] with a 96.2% [95%CI 93.2-97.9] specificity.
Conclusion: The diagnostic performance of suction drainage fluid culture after aseptic instrumented spine surgery for acute surgical site infection is insufficient to warrant its use in routine practice.