P99. Postoperative coronal malalignment after adult spinal deformity surgery: Incidence, risk factors, and impact on 2-year outcomes

Abstract

BACKGROUND CONTEXT Little is known regarding the incidence and risk factors for postop CM after ASD surgery. PURPOSE A subset of patients undergoing adult spinal deformity (ASD) surgery will have postoperative coronal malalignment (CM) with suboptimal outcomes. STUDY DESIGN/SETTING Retrospective cohort. PATIENT SAMPLE A total of 243 adult spinal deformity patients. OUTCOME MEASURES Postoperative Coronal Malalignment. METHODS A single-institution database was queried for ASD patients undergoing ≥6 level fusions from 2015-19. Postop coronal malalignment was defined as C7 coronal vertical axis (CVA) >3cm. Iatrogenic coronal malalignment was defined as postop CVA>3cm in patients without preop CM. Demographic, radiographic, and surgical variables were collected. 2-year outcomes included: complications, readmissions, reoperations, and aODI/SRS-22r. Logistic regression was performed. RESULTS A total of 243 ASD patients had preop and immediate postop measurements; 174 patients (72%) had 2-year follow-up. Mean age was 50.9±17.6 & mean instrumented levels was 13.5±3.9. Mean preop CVA was 2.9±2.7cm, and 90 (37%) had preop CM. Postop CM was seen in 43 (18%) patients, 13 (5%) of which were iatrogenic. Significant risk factors for postop CM were: EBL (OR 1.00, p=0.026), operative time (OR 1.16, p=0.045), preop CVA (OR 1.21, p=0.001), preop SVA (OR 1.05, p=0.046), pelvic obliquity (angle between horizontal & iliac crests) (OR 1.21, p=0.008), lumbosacral fractional (LSF) curve concavity to the same side as the CVA (OR 2.31, p=0.043), & max cobb angle concavity opposite the CVA (OR 2.10, p=0.033). The single significant risk factor for iatrogenic postoperative CM was a LSF curve concavity to the same side as the CVA (OR 11.39, p=0.020). Patients with postop CM were more likely to sustain a postop complication (31.0% vs 14.3%, p=0.009), yet no differences were seen in readmissions (p=0.743) or reoperations (p=1.000). No significant differences were seen in 2-year PROs according to postop coronal malalignment. CONCLUSIONS Postoperative coronal malalignment occurred in 18% of adult spinal deformity patients and was most associated with preoperative CVA, pelvic obliquity, LSF curve to the same side as the CVA, and max cobb angle to the opposite side of the CVA. Though postoperative coronal malalignment was significantly associated with increased complications, surprisingly, readmission, reoperation, & 2-year PROs were similar in those with and without coronal malalignment. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. Little is known regarding the incidence and risk factors for postop CM after ASD surgery. A subset of patients undergoing adult spinal deformity (ASD) surgery will have postoperative coronal malalignment (CM) with suboptimal outcomes. Retrospective cohort. A total of 243 adult spinal deformity patients. Postoperative Coronal Malalignment. A single-institution database was queried for ASD patients undergoing ≥6 level fusions from 2015-19. Postop coronal malalignment was defined as C7 coronal vertical axis (CVA) >3cm. Iatrogenic coronal malalignment was defined as postop CVA>3cm in patients without preop CM. Demographic, radiographic, and surgical variables were collected. 2-year outcomes included: complications, readmissions, reoperations, and aODI/SRS-22r. Logistic regression was performed. A total of 243 ASD patients had preop and immediate postop measurements; 174 patients (72%) had 2-year follow-up. Mean age was 50.9±17.6 & mean instrumented levels was 13.5±3.9. Mean preop CVA was 2.9±2.7cm, and 90 (37%) had preop CM. Postop CM was seen in 43 (18%) patients, 13 (5%) of which were iatrogenic. Significant risk factors for postop CM were: EBL (OR 1.00, p=0.026), operative time (OR 1.16, p=0.045), preop CVA (OR 1.21, p=0.001), preop SVA (OR 1.05, p=0.046), pelvic obliquity (angle between horizontal & iliac crests) (OR 1.21, p=0.008), lumbosacral fractional (LSF) curve concavity to the same side as the CVA (OR 2.31, p=0.043), & max cobb angle concavity opposite the CVA (OR 2.10, p=0.033). The single significant risk factor for iatrogenic postoperative CM was a LSF curve concavity to the same side as the CVA (OR 11.39, p=0.020). Patients with postop CM were more likely to sustain a postop complication (31.0% vs 14.3%, p=0.009), yet no differences were seen in readmissions (p=0.743) or reoperations (p=1.000). No significant differences were seen in 2-year PROs according to postop coronal malalignment. Postoperative coronal malalignment occurred in 18% of adult spinal deformity patients and was most associated with preoperative CVA, pelvic obliquity, LSF curve to the same side as the CVA, and max cobb angle to the opposite side of the CVA. Though postoperative coronal malalignment was significantly associated with increased complications, surprisingly, readmission, reoperation, & 2-year PROs were similar in those with and without coronal malalignment.