Impact of Minimally Invasive Lateral versus Open Posterior Spinal Surgery on Spinopelvic Parameters in Adult Spinal Deformity

Introduction: Minimally invasive spine surgery (MIS) has emerged as a promising advancement in treating adult spinal deformity (ASD), aiming to reduce morbidity and complications compared to traditional open approaches. Understanding spinopelvic parameters is crucial for predicting surgical outcomes and patient suitability.

Methods: A retrospective review spanning 2016-2023 included all ASD surgeries at our tertiary care center. MIS was defined as lateral interbody fusion and percutaneous screw fixation, while open techniques involved full exposure pedicle screw and rod placement. Procedures addressed multilevel fusions for scoliosis and/or kyphosis correction with uppermost instrumentation typically at L2 or higher and lower instrumentation at S1 or the pelvis. Sagittal spinopelvic parameters were assessed using Surgimap, with postoperative mismatch from the Schwab angle and age-adjusted ideals calculated. Statistical analysis utilized SPSS

Results: Data from 265 patients revealed 36 (13.6%) underwent MIS procedures. Preoperative spinopelvic parameters were comparable between MIS and open surgeries. MIS procedures involved fewer fused levels (6.3±1.6 vs. 8.5±3.3, p<.05). Preoperative pelvic incidence-lumbar lordosis (PI-LL) mismatch tended to be lower in MIS (mean difference 4.6, 95% CI -0.8-10.1, p=0.095), with significantly higher lumbar lordosis (LL) (mean difference -5.4, 95% CI -10.0- -0.84, p=0.021). MIS achieved significantly less improvement in sagittal vertical axis (SVA) compared to open (ΔSVA 2.6±1.3 mm vs. 4.7±3.5 mm; p<.05). Differences in LL correction (mean difference 3.6, 95% CI 0.62-6.6, p=0.019) and SVA (mean difference 2.1 mm, 95% CI 1.4-2.7 mm, p=0.0) favored open approaches, indicating greater correction capability compared to MIS. MIS also exhibited larger mismatches from Schwab SVA (mean difference -8.9 mm, 95% CI -16.4- -1.5 mm, p=0.02) and age-adjusted ideal SVA (mean difference -7.8 mm, 95% CI -16.8-1.2 mm, p=0.087).

Conclusion : In our cohort, MIS Lateral procedures showed less optimal adjustment of SVA and LL compared to open approaches, potentially attributed to limited osteotomy capabilities. Other spinopelvic parameters demonstrated similar outcomes between MIS and open approaches, suggesting nuanced considerations in surgical planning for ASD correction.