Correction of the Lumbosacral Fractional Curve versus Thoracolumbar Major Curves in Adult Spinal Deformity Surgery:...

In adult spinal deformity (ASD) surgery, lumbosacral fractional curve (LSF) is stiffer and harder to correct than thoracolumbar major curve (MC). In patients undergoing ASD surgery, we aimed to: 1) assess correction rate of LSF versus MC, 2) determine association between their correction and postoperative alignment and complications.

A retrospective cohort study (2009-23) including patients undergoing ASD surgery with evaluated LSF and MC. Outcomes were postoperative coronal malalignment (CM) (CVA ≥3 cm), sagittal malalignment, and mechanical complications. Multivariable regression controlled for age, sex, body mass index, and preoperative alignment.

Among 174 patients (mean age: 60 ± 19 years; 73% females), mean preoperative LSF and MC were 13 ± 10° and 32 ± 18°. Mean preoperative/postoperative CVA were 26 ± 25 mm and 20 ± 21 mm. LSF and MC and were corrected by a median of 35% (interquartile range: 0.7%-68%) and 17% (interquartile range: 3.0%-61%). Postoperative CM was seen in 35 (20%) patients. Improvement in LSF and MC occurred in 55% versus 76% (P < 0.001). Among 4-groups based on each curve correction, no significant difference was seen in postoperative CM (P = 0.060) or CVA (P = 0.316). Among patients with LSF-only versus MC-only corrected, LSF-only group had higher-risk of postoperative CM (33% vs. 10%, P = 0.038, odds ratio = 5.0, 95%CI:1.0-24.4, P = 0.048). LSF-only group had the highest postoperative sagittal vertical axis (P = 0.010), but this was lost on multivariable regression (β = 10.9, 95%CI:-13.4-35.2, P = 0.374).

LSF was corrected less frequently than MC. CM was more commonly seen when only-LSF was corrected compared to only-MC. No significant differences were noted in postoperative alignment or complications. These findings emphasize the importance of reconciling correction of both LSF and MC to avoid global CM.