22. Subclinical infection as an etiology for pseudarthrosis in multilevel thoracolumbar spinal fusions

BACKGROUND CONTEXT Pseudarthrosis is a common indication for revision spine operations. Clinical presentations of pseudarthrosis are heterogeneous. While the majority of patients present with pain, many can be symptomatic. Etiologies of pseudarthrosis also vary from structural to biologic, including infection. PURPOSE To determine prevalence of subclinical infection and identify risk factors associated with positive intraoperative cultures in revisions for lumbar pseudarthrosis. STUDY DESIGN/SETTING Single-center retrospective cohort. PATIENT SAMPLE Adults who underwent revision posterior instrumented fusions for lumbar pseudarthrosis. OUTCOME MEASURES Intraoperative microbiological analysis. METHODS Retrospective review of adults who underwent revision posterior instrumented fusions for lumbar pseudarthrosis at a single institution. All patients had intraop cultures obtained regardless of clinical suspicion for infection. Patients with overt infection were excluded. Demographic, medical, and surgical data were analyzed for association with positive cultures and instrumentation failure. RESULTS Fifty-one patients (avg age 59.1±13.2 years, female-28, avg # prior operations 3.2±2.8) were included. Seventeen (33.3%) had at least 1 positive intraop culture, and 7 (13.7%) had ≥2 positive intraop cultures. Instrumentation failure was evident in 14 (27.5%) patients. Female gender was associated with decreased odds of having ≥2 positive intraop cultures (OR=0.10, p CONCLUSIONS One third of patients undergoing revision for lumbar pseudarthrosis had subclinical infection (positive intraoperative culture). As such, intraoperative cultures should ideally be routinely obtained in the revision setting for lumbar pseudarthrosis and/or instrumentation failure regardless of clinical suspicion for infection. Further studies are necessary to identify risks of subclinical infection leading to pseudarthrosis. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.