P167. Sequential correction of sagittal vertical alignment and lumbar lordosis in adult flatback deformity

• Published in: The spine journal 2024-09, Vol.24 (9), p.S145-S145
• Main Authors: MacConnell, Ashley, Krob, Joseph, Muriuki, Muturi, Havey, Robert M., Meldau, Jason, Matteini, Lauren Elizabeth, Wojewnik, Bartosz, Baksh, Nikolas, Patwardhan, Avinash G
• Format: Article
• Language: English
• ISSN: 1529-9430
• DOI: 10.1016/j.spinee.2024.06.187

Flatback deformity causes sagittal imbalance, which leads to back pain, fatigue, and functional limitation. Biomechanical data on the effectiveness of different surgical techniques is lacking. This study investigated the correction of sagittal vertical alignment (SVA) and lumbar lordosis achieved through sequential procedures on human spine specimens. Thirteen thoracolumbar (T10-sacrum) spine specimens were CT scanned to allow kinematic assessment of vertebral position and motion. Specimens were stratified into the iatrogenic or degenerative flatback deformity group based on initial disc collapse at L5-S1 and/or L4-5 and preoperative lumbar lordosis. N/A Correction of lumbar lordosis and SVA. The procedures for degenerative specimens included anterior lumbar interbody fusion (ALIF) at L5-S1, ALIF at L4-5, lateral lumbar interbody fusion (LLIF) at L2-3 and L3-4, and posterior column osteotomy (PCO) at L2-3 and L3-4. Iatrogenic lumbar flatback specimens underwent posterior in situ fusion at L4-S1 followed by hypolordotic fusion at L4-S1 created with distraction across the pedicle screws. LLIF at L2-3 and L3-4 was then performed, followed by PCO at L2-3 and L3-4. Lumbar lordosis, L1-S1 SVA, and T10-S1 SVA were recorded initially and after each stepwise procedure. For the specimens with degenerative flatback, statistically significant incremental corrections were noted in SVA and lordosis after the L5-S1 ALIF, L4-5 ALIF, and PCO. A statistically significant difference was also noted in overall correction when comparing preoperative values to those after completion of the PCO. The average correction obtained with these procedures was: T10-S1 SVA -116.7±17.8 mm, L1-S1 SVA -64.9±9.2 mm, and L1-S1 lordosis -32.6±10.5 degrees. For the iatrogenic group, a statistically significant worsening was noted in all three measures with performance of the hypolordotic fusion across L4-S1. Subsequent LLIF at L2-3 and L3-4 did not show significant improvement in sagittal alignment. However, with the addition of PCO at L2-3 and L3-4, the final alignment parameters approached their preoperative values (P>0.01). ALIF cages in the lower lumbar segments significantly improved sagittal alignment in adult degenerative flatback deformity. LLIF cages in the upper lumbar segments by themselves were not effective in correcting SVA or enhancing lordosis. LLIF cages in conjunction with PCO improved alignment parameters in both degenerative and iatrogenic flatback deformities. This abstract