Interbody device placement in thoracolumbar scoliosis malalignment affects mechanical complications and outcomes

BACKGROUND CONTEXT: Focal coronal malalignment in the lower lumbar spine can place significant forces on the construct and can be a challenge to correct. The use of supplemental rods and interbody devices (IBD) can potentially reduce rates of mechanical failures and pseudarthrosis and has yet to be evaluated. PURPOSE: To determine whether the use of multiple rods above IBD in those with focal coronal deformity improves outcomes. STUDY DESIGN/SETTING: Retrospective cohort study of a prospectively collected single-center adult spinal deformity database. PATIENT SAMPLE: Coronal ASD. OUTCOME MEASURES: N/A METHODS: Primary operative ASD patients with coronal malalignment undergoing at least 5 level fusion from sacrum with 2Y follow-up were included. Patients with supplemental rods were evaluated in subanalysis. Patients with coronal malalignment were defined as having >20 degrees coronal Cobb angle and C7-S1 coronal vertical axis (CVA) >30mm. Patients were analyzed based on the apex of the coronal curve in relation to the placement of IBD to determine rates of mechanical complications. Patients were stratified based on whether IBD extended proximal (P) to apex from sacrum were compared to those without (NP). Furthermore, patients were stratified based on supplemental rod construct. Mechanical complications, HRQLs, and radiographic alignment durability from postoperative to 2Y was assessed. Descriptive analysis and means comparison tests were used. ANCOVA and multivariable regression controlled for baseline variances. RESULTS: A total of 242 patients met inclusion (Age 63, 85% F, CCI 1.9). The mean baseline max cobb angle was 47±18°, apex was L1 (SD ± 2 levels), and CVA was 67 38mm. P at baseline had worse SVA, loss of lumbar lordosis, and PI-LL mismatch. No difference in coronal Cobb angle, or CVA amongst IBD distal to apex compared to those that had proximal placement. The coronal apex was more proximal in those with IBD placed below the apex (T12 vs L2, p<0.001). Patients with IBD distal to apex had higher rates of postoperative coronal imbalance (0% vs 5%, p=0.014), despite those with proximal to apex having worse CCI (2.3 vs 1.7, p=0.03) and frailty (3.7 vs 3.2, p=0.03). CONCLUSIONS: Despite having worse baseline sagittal deformity, comorbidity burden, and frailty, patients with IBD extending proximal to the coronal apex were less likely to have residual postoperative coronal imbalance and deterioration of alignment. FDA Device/Drug Status: This abstract does not discuss or include any applicable devices or drugs.

Duke Scholars

Author Christopher Ignatius Shaffrey Orthopaedic Surgery

Author Peter Passias Orthopaedic Surgery