Proximal lumbar anterior column realignment for iatrogenic sagittal plane adult spinal deformity correction: a retrospective case series.

Background and objectives: Anterior column realignment (ACR) is a powerful minimally invasive surgery (MIS) technique to restore sagittal alignment in adult spinal deformity (ASD). This can accomplish similar segmental lordosis restoration as 3-column osteotomy with less blood loss and comparable complication rates. ACR can be performed at adjacent disease segments in the proximal lumbar spine in revision cases. However, two-thirds of physiologic lordosis occurs between L4-S1, and concerns remain about altered lumbar morphology. We evaluated patients who underwent proximal lumbar ACR for iatrogenic flatback deformity.

Methods: A total of 19 consecutive patients who underwent L1-2 or L2-3 ACR were retrospectively analyzed. All patients were treated with lateral MIS interbody technique, followed by posterior reconstruction with Smith-Peterson osteotomy (SPO). Pre- and post-operative radiographic and clinical outcomes were obtained.

Results: Mean follow-up was 19-months. All but one patient had a history of prior lumbar or lumbo-sacral fusion. SVA and PI-LL decreased from 11.9 cm to 6.1 cm (p<0.0001) and 34.2° to 12.8° (p<0.0001). Segmental lordosis increased from -2.7° to 21.9° (p<0.0001). Proximal lumbar lordosis (PLL) increased from -0.4° to 22.6° (p<0.0001), and lordosis distribution index (LDI) decreased from 79.5% to 48.9% (p<0.0001). Mean ODI and NPRS back pain decreased from 58.0 to 36.2 (p=0.0041) and 7.9 to 3.4 (p<0.0001). PROMIS-10 Physical and Mental Health T-scores increased from 34.1 to 43.3 (p=0.0049) and 40.4 to 45.0 (p=0.0993). Major complication rate was 15.8%. One patient required revision for mechanical failure. There were no permanent neurological or vascular injuries.

Conclusion: Proximal lumbar ACR plus SPO can achieve sagittal correction with low major complication rates in patients with ASD and prior distal fusion. Differentially increasing PLL and lowering LDI did not have deleterious effects on radiographic or clinical outcomes. Further work is needed to understand the effect of proximal ACR in the surgical management of ASD.