BACKGROUND CONTEXT Ehlers Danlos Syndrome (EDS) is a rare connective tissue disorder that results from mutations in collagen genes. Potentially related to laxity and resultant degenerative changes, adult EDS patients may require posterior lumbar fusion (PLF). However, with low numbers, adequately powered outcome studies have been limited. PURPOSE To investigate the effect of Ehlers Danlos Syndrome on postoperative outcomes and reoperations following PLF. STUDY DESIGN/SETTING Retrospective cohort study using the 2010 - 2020 MSpine Pearldiver dataset. PATIENT SAMPLE Patients with a diagnosis of EDS (any type) were identified using International Classification of Diseases (ICD) codes. Patients over 18 years of age undergoing PLF with or without laminectomy were identified using Current Procedural Terminology (CPT) codes. Patients who had a primary diagnosis code of fractures, infection, neoplasm or were not in the database for at least 90 days following the surgery were excluded. Further, patients who had multilevel fusions or had concurrent anterior fusion were excluded. OUTCOME MEASURES Ninety-day any, severe, and minor adverse events as well as readmissions and five-year reoperations. METHODS Adult patients undergoing single-level PLF (excluding any with anterior procedures) with and without EDS for which at least 90-day follow up was available were identified. Any cases performed for trauma, tumor, or infection were excluded. Single-level PLF EDS patients were then matched 1:4 with PLF non-EDS patients based on age, sex and Elixhauser Comorbidity Index (ECI). Rates of 90-day any, severe, and minor adverse events as well as readmissions were tabulated and compared with chi-square tests. Multivariate logistical regression was then performed (controlling for age, and ECI). Reoperation surgeries over five years were assessed, Kaplan-Meier survival curves generated, and curves of those with and without EDS were compared with log rank test. RESULTS In total, there were 170,100 single-level PLF case identified, of which 242 (0.14%) had EDS. After matching, there were 957 without EDS and 239 with EDS. On multivariate regression, there were no significant differences in 90-day any, severe, or minor adverse events, or readmissions (p>0.05 for each). Over five years, there were also not significant differences in rates of reoperation (p> 0.05). CONCLUSIONS For EDS patients undergoing PLF, the current study identified similar 90-day adverse events and five-year reoperation rates compared to those without EDS. These findings may be useful for patient counseling and surgical planning for those with this rare condition. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. Ehlers Danlos Syndrome (EDS) is a rare connective tissue disorder that results from mutations in collagen genes. Potentially related to laxity and resultant degenerative changes, adult EDS patients may require posterior lumbar fusion (PLF). However, with low numbers, adequately powered outcome studies have been limited. To investigate the effect of Ehlers Danlos Syndrome on postoperative outcomes and reoperations following PLF. Retrospective cohort study using the 2010 - 2020 MSpine Pearldiver dataset. Patients with a diagnosis of EDS (any type) were identified using International Classification of Diseases (ICD) codes. Patients over 18 years of age undergoing PLF with or without laminectomy were identified using Current Procedural Terminology (CPT) codes. Patients who had a primary diagnosis code of fractures, infection, neoplasm or were not in the database for at least 90 days following the surgery were excluded. Further, patients who had multilevel fusions or had concurrent anterior fusion were excluded. Ninety-day any, severe, and minor adverse events as well as readmissions and five-year reoperations. Adult patients undergoing single-level PLF (excluding any with anterior procedures) with and without EDS for which at least 90-day follow up was available were identified. Any cases performed for trauma, tumor, or infection were excluded. Single-level PLF EDS patients were then matched 1:4 with PLF non-EDS patients based on age, sex and Elixhauser Comorbidity Index (ECI). Rates of 90-day any, severe, and minor adverse events as well as readmissions were tabulated and compared with chi-square tests. Multivariate logistical regression was then performed (controlling for age, and ECI). Reoperation surgeries over five years were assessed, Kaplan-Meier survival curves generated, and curves of those with and without EDS were compared with log rank test. In total, there were 170,100 single-level PLF case identified, of which 242 (0.14%) had EDS. After matching, there were 957 without EDS and 239 with EDS. On multivariate regression, there were no significant differences in 90-day any, severe, or minor adverse events, or readmissions (p>0.05 for each). Over five years, there were also not significant differences in rates of reoperation (p> 0.05). For EDS patients undergoing PLF, the current study identified similar 90-day adverse events and five-year reoperation rates compared to those without EDS. These findings may be useful for patient counseling and surgical planning for those with this rare condition.