Wednesday, September 26, 2018 3:35 PM – 5:05 PM How to Avoid Complications: 95. Factors associated with the decision to culture and positive growth in aseptic revision spine surgery

Abstract

BACKGROUND CONTEXT The indications for obtaining cultures in revision spinal surgery remain unclear in the absence of a definitive diagnosis of infection. Surgeon behavior related to obtaining cultures and risk factors for positive cultures in this setting have not been previously studied. PURPOSE To report on the specimen collection patterns and culture results during presumed aseptic revision spine cases. An improved understanding of what leads surgeons to exclude infection as well as the risk factors for having a positive culture will help inform future culturing practices, highlighting underlying characteristics which may increase the yield of taking intraoperative cultures in presumed aseptic revision cases. This data will aid surgeons, hospitals, and payers in what is currently a challenging clinical scenario. STUDY DESIGN/SETTING Retrospective review. PATIENT SAMPLE A total of 578. OUTCOME MEASURES Factors associated with the decision to obtain cultures intraoperatively in cases of aseptic revision spine surgery; risk factors for positive cultures obtained in such cases METHODS Following approval of the institutional review board, 595 consecutive revision spine surgeries performed by four senior surgeons between 2008 and 2013 were retrospectively reviewed. All revision surgeries including the cervical, thoracic, and lumbosacral spine employing fusion and non-fusion techniques with and without instrumentation were included. Routine preoperative evaluation of each of these patients included clinical examination, radiographs, and advanced imaging. In cases of suspected infection, preoperative measurement of serum white blood cell count, erythrocyte sedimentation rate, and C-reactive protein were obtained. The primary diagnosis at the time of revision surgery was identified in each case by the first ICD-9 code listed at the time of surgery. Cases were presumed aseptic if the principle preoperative diagnosis was not infection. Preoperative work-up revealed the diagnosis of infection in 17 cases which were excluded. A detailed chart review was performed on the remaining 578 cases. RESULTS Cultures were obtained in 112 (19.4%) cases and were positive in 40.2%. Pseudarthrosis was the most common revision diagnosis when cultures were obtained (49.1%) and Propionibacterium acnes was the most common organism isolated from positive cultures (48.8%). Multivariate analysis demonstrated that obesity (OR=2.4), instrumentation (OR=2.4), thoracolumbar surgery (OR=5.2), and diagnosis of implant failure (OR=9.0) or pseudarthrosis (OR=8.0) were significantly correlated with decision to culture while time between index and revision procedures (OR=0.9) and cervical surgery (OR=0.2) were negatively correlated, with AUC 0.85. Regarding culture results, multivariate analysis demonstrated that male sex (OR=3.4) and pseudarthrosis (OR=4.1) were significantly associated with having positive cultures while fusion procedures (OR = 0.3) were negatively correlated, with AUC 0.71. CONCLUSIONS Unexpected positive cultures occurred commonly and Propionibacterium acnes was the predominant isolated organism. Obesity, instrumentation, thoracolumbar surgery, implant failure, and pseudarthrosis all predicted culture collection. Male sex, pseudarthrosis, and non-fusion cases predicted positive cultures. Considering these results, we recommend cultures be obtained in revision cases for pseudarthrosis, even in the setting of negative infectious work-up preoperatively. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.