total of 27 complications including a 64.7% rate of PJK and a 35.3% rate of reoperation. CONCLUSIONS: Elderly patients $75 years undergoing ASD surgery had significantly improved HRQOL and radiographic measures over base- line at two years compared to a similar nonoperative cohort, despite sub- stantial operative morbidity. This data may be used for preoperative patient counseling in this high-risk elderly population. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.058 40. Predictors of Revision Surgery in Adult Spinal Deformity and Impact on Patient-Reported Outcomes and Satisfaction: Two-Year Follow-Up International Spine Study Group 1 , Peter G. Passias, MD 2 , Sun Yang, BA 3 , Alexandra Soroceanu, MD, MPH 4 , Justin S. Smith, MD, PhD 5 , Christopher I. Shaffrey, MD 6 , Oheneba Boachie-Adjei, MD 7 , Gregory M. Mundis, Jr., MD 8 , Christopher P. Ames, MD 9 , Douglas C. Burton, MD 10 , Shay Bess, MD 11 , Eric O. Klineberg, MD 12 , Robert A. Hart, MD 13 , Frank J. Schwab, MD 3 , Virginie Lafage, PhD 3 ; 1 Brighton, CO, US; 2 Brooklyn, NY, US; 3 New York University Langone Medical Center Hospital for Joint Diseases, New York, NY, US; 4 Dalhousie University, Halifax, NS, Canada; 5 University of Virginia Health System, Charlottesville, VA, US; 6 University of Virginia Department of Neurosurgery, Charlottesville, VA, US; 7 Hospital for Special Surgery, New York, NY, US; 8 San Diego Center for Spinal Disorders, La Jolla, CA, US; 9 University of California San Francisco, San Francisco, CA, US; 10 University of Kansas Medical Center, Kansas City, KS, US; 11 Rocky Mountain Scoliosis and Spine, Denver, CO, US; 12 University of California Davis School of Medicine, Sacramento, CA, US; 13 Oregon Health and Science University, Portland, OR, US BACKGROUND CONTEXT: Patients undergoing adult spinal de- formity (ASD) correction are at risk for an unplanned return to sur- gery due to complications following index surgery vs primary outcomes. Revision surgeries are often more technically challenging, and therefore, it is important to identify predictors to be included in preoperative discussion and to notify known risk factors to patients. However, there is no literature proposing predictors of revision sur- gery for ASD patients. PURPOSE: To investigate the incidence, predictors and impact on health- related quality of life (HRQL) outcomes and patient satisfaction of unplanned return to surgery after ASD correction. STUDY DESIGN/SETTING: Multicenter, retrospective review of con- secutive surgical ASD patients. PATIENT SAMPLE: 243 adults treated surgically for spinal deformity. OUTCOME MEASURES: Pre- and postoperative HRQL scores and ra- diographic parameters, rate and predictors of revision surgery. METHODS: Two-year, multicenter, prospective analysis of surgical adult spinal deformity (ASD) patients (age $18 years and scoliosis $20  , SVA $5cm, pelvic tilt $25  , or thoracic kyphosis O 60  ). Inclusion criteria for this study were complete demographic, radiographic, HRQL and operative data at 2-year follow-up. Patients were divided into Index Surgery only or Revisions. Primary infections were excluded. Potential predictors and confounders for revision surgery were identified using univariate analysis. Multivariate logistic regression modeling determined predictors of revision and impact on satisfaction. Multivariate repeated measured mixed models measured revision impact on HRQL. RESULTS: 243 patients met inclusion criteria. 42 (17.3%) patients under- went revisions (14.3% at 6 weeks, 38% between 6 weeks and 1 year, and 47.7% between 1-2 years). Non-rod implant complications were the most common indication for revision (9) followed by PJK (8) and rod failure (8). Positive predictors of revision surgery included: weight (OR 1.33 per 10kg increase weight, p50.021) and SVA (OR 1.15 per 2cm increase in SVA, p50.006). Negative predictors included use of BMP2 (OR 0.157, p50.001) and thicker rods (OR 0.5, p50.018). HRQL improved in all patientsdSF-36 (p50.0001), ODI (p50.0001) and SRS (p50.0001)dbut the rate (SF-36 p50.02) and overall improvement (SRS p50.016) com- pared to baseline were less for revisions. Revision status did not predict 2-year satisfaction (p50.726). CONCLUSIONS: Overweight patients with greater pre-op global sagittal malalignment are at greater risk for revision surgery following ASD cor- rection. Using thicker rods and BMP2 was associated with decreased odds of revision. Revisions did not impact patient satisfaction at 2 years. Pa- tients with revisions saw significant improvements in HRQL albeit less than those without. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.059 41. Reaching Minimal Clinically Important Difference through Nonoperative Treatment of Adult Spinal Deformity International Spine Study Group 1 , Shian Liu, BS 2 , Barthelemy Liabaud, MD 3 , Justin S. Smith, MD, PhD 4 , Richard A. Hostin, MD 5 , Christopher I. Shaffrey, MD 6 , Matthew E. Cunningham, MD, PhD 7 , Gregory M. Mundis, Jr., MD 8 , Christopher P. Ames, MD 9 , Douglas C. Burton, MD 10 , Shay Bess, MD 11 , Behrooz A. Akbarnia, MD 8 , Robert A. Hart, MD 12 , Frank J. Schwab, MD 2 , Virginie Lafage, PhD 2 ; 1 Brighton, CO, US; 2 New York University Langone Medical Center Hospital for Joint Diseases, New York, NY, US; 3 New York University, New York, NY, US; 4 University of Virginia Health System, Charlottesville, VA, US; 5 Southwest Scoliosis Institute, Plano, TX, US; 6 University of Virginia Department of Neurosurgery, Charlottesville, VA, US; 7 Hospital for Special Surgery, New York, NY, US; 8 San Diego Center for Spinal Disorders, La Jolla, CA, US; 9 University of California San Francisco, San Francisco, CA, US; 10 University of Kansas Medical Center, Kansas City, KS, US; 11 Rocky Mountain Scoliosis and Spine, Denver, CO, US; 12 Oregon Health and Science University, Portland, OR, US BACKGROUND CONTEXT: A large percentage of patients with adult spinal deformity (ASD), up to 52% in the literature, gain a minimal clin- ically important difference (MCID) in one or more of the health-related quality of life (HRQOLs) instruments. PURPOSE: This study attempts to identify and describe baseline charac- teristics of this subset of nonoperative patients who improve, and propose possible predictors of MCID gain in SRS Activity or Pain. STUDY DESIGN/SETTING: Post-hoc analysis of prospective, multicen- ter database of operative and nonoperative patients with ASD. PATIENT SAMPLE: 215 nonoperative patients with ASD with minimum 2-year follow-up and an MCID deficit in either SRS Activity or Pain. OUTCOME MEASURES: SRS Activity, SRS Pain, MCID, spinopelvic radiographic parameters. METHODS: Post-hoc analysis of prospective, multicenter, case series of 215 nonoperative patients with ASD with minimum 2-year follow-up and an MCID deficit (need for improvement) at baseline in SRS Pain or Activ- ity scores compared to the normative population. Using a multivariate analysis, 2 groups were compared to identify possible predictors: those that reached an MCID in SRS Pain or Activity (n586) at 2 years and those that missed MCID (n5129). RESULTS: At baseline, 215 nonoperative patients with ASD needed to improve in SRS Activity or Pain, and there were no statistically significant differences in age, BMI or baseline SVA (17.5mm v 20.5mm p 0.70) be- tween the cohorts that improved and did not improve. At 2-year follow- up, 40% (n 5 86) reached MCID and 60% (n 5 129) missed MCID. Of the nonoperative patients who reached MCID at 2 years, they had at base- line a significantly lower SRS Pain (3.0 v 3.6, p ! 0.05), thoracolumbar 21S Proceedings of the NASS 29th Annual Meeting / The Spine Journal 14 (2014) 1S–183S Refer to onsite Annual Meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosures and FDA device/drug status at time of abstract submission.