Prevalence and Prognosis of Coronal Malalignment Following Lateral Lumbar Interbody Fusion for Minimally Invasive Treatment of Adult Spinal Deformity

Abstract

Study Design. – Retrospective analysis of prospective multicenter adult spinal deformity (ASD) database. Objective. – To determine the prevalence and prognosis of postoperative coronal malalignment following LLIF for ASD with Qiu type A coronal alignment. Summary of Background Data. – Qiu type A coronal alignment is defined as coronal vertical axis (CVA) <30 mm. There is concern that circumferential minimally invasive surgery (cMIS) with lateral lumbar interbody fusion (LLIF) is associated with postoperative coronal malalignment in ASD with preoperative Qiu type A patients. Materials and Methods. – Qui type A patients undergoing cMIS with LLIF for ASD were included, with ASD defined with at least: maximum CC ≥20°, SVA >5 cm, PI-LL ≥10°, or PT >20°. Two-year (2Y) clinical outcomes were compared for type A with 2Y CVA ≥30 mm (MAL) versus <30 mm (ALIGN) and were adjusted for factors reaching P<0.05 on univariate comparisons (age, BMI, and ODI). Results. – Forty-three patients met inclusion criteria, of which 12 (27.9%) developed coronal malalignment and 31 (72.1%) remained coronally aligned at 2Y. At baseline, MAL were older (73.0 vs. 69.0, P=0.045), had a lower BMI (26.09 vs. 29.45, P=0.045), and were less disabled (ODI: 42.83 vs. 51.69, P=0.02). Otherwise, the groups were well-matched for baseline characteristics. At 2Y, MAL had a greater 2Y SVA (mean: 54.08 vs. 19.00 mm, P=0.01). Clinically, MAL was associated with inferior 2Y SF-36 PCS (34.78 vs. 37.42, adj P=0.04) and 2Y SRS-22r function/activity domain (3.03 vs. 3.36, adj P=0.04), but otherwise similar in other patient-reported outcome metrics (adj P>0.05 for all). 2Y complications were similar between groups, including for reoperations and major and minor complications (adj P>0.05 for all). Conclusions. – In Qui type A patients undergoing cMIS with LLIF for ASD, 27.9% develop coronal malalignment, which was associated with worse SF-36 PCS and SRS-22r function/activity. Despite radiographic malalignment, malalignment was not associated with higher two-year complication rates including reoperations.