PURPOSE: Sacral disease requiring sacrectomy is relatively rare, and reconstructing the ensuing defects involves challenging decisions. Significant rates of post-operative complications are documented in the literature and a lack of consensus on optimal reconstructive strategies persists. The purpose of this study is to review the experience of a single institution with reconstructing large sacral defects following partial or total sacrectomy, to identify risk factors for sub-optimal outcomes. METHODS: Following institutional review board approval, a retrospective chart review was conducted looking at post-operative complications following sacrectomy. All patients who underwent partial or total sacrectomy at our institution between December 2009 and March 2017 were included. Data on patient co-morbidities, surgical history, chemoradiation, operative course, and long-term outcomes was collected. A univariate analysis of differences in risk factors between patients with and without various post-operative complications was performed using Fisher’s exact test. All statistical tests were completed with SAS version 9.4 (SAS Institute, Inc., Cary, NC). Significance was defined as p=0.05 and non-significant trends were defined as p=0.15. RESULTS: A total of 28 patients were included in the study. Average age was 62 years and mean length of follow-up was 20 months. The most common diagnosis leading to sacrectomy was chordoma (39%). Total sacrectomy was performed on 4 patients, while 24 patients underwent partial resection of the sacrum. Complex composite defects, which averaged 1230 cm3 in volume, were most often reconstructed with gluteal-based flaps (n = 15). There was an overall complication rate of 57.1% (n=12) and a 28.6% (n=8) incidence of major complications. There were significantly more flap-related complications in patients who underwent total sacrectomy (p=0.02) and had larger sacral defects (p <0.05). Total sacrectomy resulted in significantly more unplanned returns to the operating room (p <0.01) and hospital stays exceeding 2 weeks (p< 0.01). Interestingly, concurrent colostomy and/or ileostomy showed a trend towards higher rates of infection resulting in abscess (p= 0.06), return to the operating room (p=0.06), and extended hospital stay (p= 0.10). Choice of reconstruction was significantly related to infection resulting in abscess (p<0.05) and return to the operating room (p< 0.01). Rectus abdominis flaps were associated with complications in all but one patient. CONCLUSION: Consistent with other published series, the overall sacrectomy-associated complication rate exceeded 50 percent. Incidence of major complications was lower in our series than previously reported by other groups. Defect volume and sacrectomy type were the strongest predictors of post-operative complications and return to the operating room, while reconstructive strategy showed limited power to predict patient outcomes. Based on this data, we recommend that patients with large sacral defects should be appropriately counseled regarding the incidence of wound complications, regardless of reconstructive approach. E. Vartanian: None. J. Lynn: None. D. Perrault: None. E. Wolfswinkel: None. K. Patel: None. P. Hsieh: None. A. Wong: None.