P28. Bone mineral density t-score is an independent predictor of significant blood loss in adult spinal deformity surgery

Abstract

BACKGROUND CONTEXT Blood loss is an important cause of morbidity in Adult Spinal Deformity (ASD) surgery. Thus, identifying potentially modifiable factors associated with increased EBL in ASD surgery is important. Bone mineral density (BMD), as measured by Dual-energy X-ray Absorptiometry (DEXA), is important for stable instrumented fixation and is often measured preoperatively in ASD patients. However, the association between BMD and intraoperative blood loss in ASD patients has not been studied. PURPOSE Lower BMD is associated with greater odds of major blood loss in ASD surgery. STUDY DESIGN/SETTING Cross-sectional study from a single surgeon at an academic institution. PATIENT SAMPLE A total of 91 ASD patients (>5 levels fused) who had preoperative DEXA score recorded within the year preceeding surgery. OUTCOME MEASURES Our primary outcome was major blood loss, defined as >2L of estimated blood loss, using the upper 90th percentile of our study population. METHODS The lowest preoperative T-score was recorded. Patients were excluded who had liver/kidney disease or were on prescription anticoagulant medication. Binomial regression was performed controlling for age, number of vertebra fused, 3-column osteotomy, primary vs. revision surgery, preoperative platelet count, and if the patient was taking medication for osteoporosis. Significance was set at p=0.05. RESULTS Mean age of patients was 63 ± 11.6 years, 81% female. 56 (62%) of cases included revision of previous instrumentation. Patients had a mean SVA of 9.6 ± 8.6cm and median of 9 vertebra fused (range 5-22). The average T-score was -1.2 ± 1.0. Each point lower T-score was associated with significantly higher odds of major blood loss (OR 2.5, 95% CI 1.0 – 5.9) when controlling for age, number of vertebra fused, 3-column osteotomy, preoperative platelet count and primary vs. revision surgery. CONCLUSIONS Lower preoperative T-score is independently associated with increased odds of significant blood loss in ASD surgery. Surgeons should anticipate increased blood loss in ASD patients with lower bone mineral density. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.