DOS 2018

190 · DOS Abstracts Is Non-union after Spinal Instrumentation Caused by a Chronic Infection? Søren Ohrt-Nissen, Blaine Fritz, Lars Valentin, Kragh Kasper N, Claus Manniche, Benny Dahl, Thomas Bjarnsholt Department of Orthopedic Surgery, Spine unit, Copenhagen University Hospital, Rigshospitalet; Department of Immunology and Microbiology., University of Copenhagen, Faculty of Health Sciences; Spine Centre of Southern Denmark, University of Southern Denmark; Department of Orthopaedic Surgery, Texas Children’s Hospital and Baylor College of Medicine, Houston, TX, USA; Department of Clinical Microbiology, Copenhagen University Hospital, Rigshospitalet Background: Instrumented spinal fusion for adult spinal deformity is associ- ated with a high revision rate with non- union as the most frequent complica- tion. Weather spinal non-union has a microbiological causation has not yet been examined. Purpose / Aim of Study: To access whether a chronic bacterial infection is present in a subset of patients with non-union after instrumented spinal fusion. Materials and Methods: The study included adult patients with previous in- strumented spinal fusion undergoing revision surgery for either non-union (case group) or other causes (control group). Five separate biopsies were collected, intraoperatively, from the non-union site and cultivated for 14 days under an- aerobic conditions. If cultivation was positive in at least 2/5 tissue samples, the biopsy was sectioned and stained by fluorescence in situ hybridization Confocal laser scanning microscopy was used to examine the sections and visualize bac- terial aggregates. Findings / Results: The study included 32 non-union and 32 control patients. Cultivation yielded bacteria in at least 1/5 biopsies in 52% of patients with no difference between the groups (p=1.0). Bacteria of the same species was found in at least 2/5 samples in 7 non- union patients and 4 controls (p=0.509). P. acnes was found in 8 of these 11 samples. Microscopy demonstrated tissue- embedded bacterial aggregates in only one of these patients. The presence of bacteria was not associated with the number of previous spinal procedures or the pre-revision fusion length (p≥0.503). Conclusions: Non-union after instrumented spinal surgery was not significantly associated with the presence of bacteria at the non-union site. Positive cultiva- tion results are common after spinal instrumentation but should be supported by other diagnostic modalities in the absence of clinical signs of infection. 131.