Suction Drain Tip Culture after Spine Surgery: Can It Predict a Surgical Site Infection?

STUDY DESIGN: Retrospective clinical study. PURPOSE: To assess the diagnostic value of suction drain tip culture in patients undergoing primary posterior spine surgery. OVERVIEW OF LITERATURE: To date, the diagnostic value of suction drain tip culture for predicting surgical site infection (SSI) has not been firmly established in orthopedic or spinal surgery. METHODS: In total, 133 patients who underwent primary posterior spine surgery from January 2013 to April 2015 were included in this retrospective study. Patients diagnosed with infective disease or condition was excluded. The suction drain tip was cut off approximately 5 cm from its far end. The sample was sent to the microbiological laboratory of the hospital for culture analysis. Any signs of infection, such as wound discharge or dehiscence, fever, chills, or chronic pain, were recorded. The culture outcome, identification of bacteria, and postoperative transition of the serum C-reactive protein level were also recorded in all patients. The wounds were followed up for a minimum of 3 months. RESULTS: A positive drain tip culture was found in 48 patients (36.1%), of whom, 6 developed SSI. The sensitivity of drain tip culture for SSI after primary posterior spine surgery was 60.0%, and the specificity was 65.9%. The association between the incidence of positive suction tip culture and SSI was not statistically significant. Among the 48 positive drain tip cultures, there was no significant association between the occurrence of SSI and virulence of isolated bacteria. There was no significant association between drain tip culture positivity and the duration of drainage, or between the rate of SSI and duration of drainage. CONCLUSIONS: Suction drain tip culture analysis is a poor predictor of SSI after primary posterior spine surgery. Routine use of a drain tip culture is not supported by the results of this study.