Are We Getting Better at Achieving Optimal Lumbar Segmental Sagittal Alignment in Complex Adult Spine Deformity Surgery?

Introduction: The understanding of sagittal spine alignment and Adult Spinal Deformity (ASD) management continues to advance. However, it remains unknown how these advances have influenced lumbar segmental alignment changes in the setting of surgical reconstruction.

Methods: Patients undergoing primary thoracolumbar fusion for ASD were stratified based on enrolment in two distinct multicenter registries; forming an ‘Early cohort’ (2008-2017) and a ‘Late cohort’ (2018-present). Patients were further stratified based on pelvic incidence (PI) and Roussouly type. Segmental alignment was determined based on published values of asymptomatic individuals. Pelvic incidence-based alignment and Roussouly-based alignment were determined in alignment with previously published normative values. Means comparisons tests and multivariate analyses compared segmental & regional parameters between groups.

Results: We included 1240 patients in the analysis (622 EARLY, 618 LATE). The mean age was 61.4 ± 14.5 years, the mean body mass index (BMI) was 28.0 ± 5.8 kg/m2, and the mean Charlson comorbidity index (CCI) was 1.55 ± 1.70. 70.2% of patients were female gender. LATE consistently displayed better L5-S1 alignment across all PI and Roussouly types (p=0.001) However, EARLY demonstrated better L4-5 alignment (p=0.001). Improved alignment in L5-S1, L4-5 and L3-4 was associated with achieving minimum clinically important difference in ODI scores and decreased risk of mechanical complications. Both cohorts demonstrated low rates of matching L4-S1 regional and overall lumbar lordosis L1-S1 alignment, with no differences between both groups. By lordosis distribution index, both groups had predominantly hyperlordotic maldistribution postop, but LATE had more ‘Aligned’ patients (15.9 vs 11%, p< 0.001).

Conclusion : Over the past 15 years, surgeons appear to be better at restoring ideal lumbar segmental sagittal alignment in patients treated surgically for ASD. However, idealized correction does not appear to be uniform across all lumbar segments, representing an opportunity for further improvement.