Does LLIF Malalign Patients with Convex Coronal Malalignment? An Analysis of the Obeid Coronal Malalignment Classification

Introduction: Compared to concave coronal malalignment (CM) (Obeid Type 1 [O1] CM>20 mm), there is a concern that lateral lumbar interbody fusion (LLIF) for convex CM (Obeid Type 2 [O2] CM>20 mm) may worsen coronal alignment. We compared 2-year (2Y) LLIF outcomes for concave and convex CM using the Obeid Classification.

Methods: This was a bispective analysis of a multicenter adult spinal deformity (ASD) database. Patients undergoing cMIS LLIF for ASD with CM>20 mm (Obeid) were included. 2Y outcomes were adjusted for age and preoperative SVA.

Results: Overall, 85 patients were prospectively enrolled with 2Y follow-up—30 met inclusion criteria (14 O1 [46.7%];16 O2 [53.3%]). O1 were older and had higher preop SVA than O2 (p < 0.05). Otherwise O1/O2 were well matched. Of note, only 1 patient in each O1/O2 cohort had fusions that did not involve the fractional curve (FC). There was no difference between O1/O2 for 2YCVA (38.2 vs. 34.4 mm, p=0.851), 2YΔCVA (Δ-7.4 vs. -10.4 mm, p =0.256), and 2YΔ max coronal cobb (CC) (Δ-7.6 vs. -10.1º, p=0.922), respectively. A similar proportion reached 2YCVA < 20 mm (O1:35.7% vs. O2:31.3%, p=0.550). There were no other significant differences for 2Y CC, SVA, PI-LL, PT, and FC (p>0.05) for O1/O2. Clinical outcomes and complications were similar (p>0.05) for O1/O2 at 2Y.

Conclusion : Following cMIS for ASD with CM, patients undergoing LLIF with convex CM did not have a significant worsening of coronal alignment and shared similar coronal parameters as LLIF for concave CM. This may be due to control of the fractional curve in the convex CM surgeries. Radiographic and clinical outcomes, and complications, were similar for O1/O2.