1209 Does the Volume of Bone Graft and Use of rhBMP-2 Impact Mechanical Complications and Patient Reported Outcomes in Adult Spinal Deformity Surgery?

INTRODUCTION: Sparse literature exists regarding the impact of bone graft volume utilized during ASD surgery on outcomes. METHODS: A single-institution, retrospective cohort study was performed for patients undergoing ASD surgery from 2009-21. The primary exposure variables were: 1) bone graft volume (ml) divided by the level fused and 2) the type of bone used (demineralized bone matrix (DBM), cancellous bone or rhBMP-2). Multivariable regression model included age, t-score, total volume, DBM, cancellous bone, and rhBMP-2 use. RESULTS: Among 238 patients undergoing ASD surgery, the range of bone graft volume per level fused was 0.3-25.7ml, mean=8.1±4.9ml. Patients with previous fusions had a higher bone graft volume (9.3±5.2 vs. 7.5±4.6, p=0.012) than those without prior fusions. Postoperatively, increased bone graft volume was associated with a lower rate of pseudarthrosis (6.4±4.4 vs. 8.8±4.9ml, p<0.001), fewer spinopelvic mechanical complications (7.03±4.9 vs. 8.6±4.8ml, p=0.022), and fewer mechanical complications requiring reoperation (6.5±4.2 vs. 8.9±5.0ml, p<0.001). However, on multivariable regression controlling for age, t-score, DBM, cancellous bone and rhBMP-2 use, rhBMP-2 use was the only variable associated with decreased odds of mechanical complications requiring reoperation (OR=0.18, 95%CI=0.07-0.48, p<0.001), pseudarthrosis (OR=0.07, 95%CI=0.02-0.24, p<0.001), and spinopelvic mechanical complications (OR=0.21, 95%CI=0.08-0.53, p<0.001). CONCLUSIONS: In patients undergoing ASD surgery, utilization of rhBMP-2 resulted in significantly decreased mechanical complications and improved fusion rate, whereas the total volume or type of allograft bone did not significantly impact postoperative outcomes.