Segmental Lordosis and Disc Height Discrepancies in Lateral Lumbar Interbody Fusion Using Expandable Cages

<sec><title>Background</title> This study evaluated discrepancies between the expected intervertebral disc height (DH) and segmental lordosis (SL), defined as predicted values based on the rotations of the expandable cage driver, and the actual DH and SL achieved postoperatively in lateral lumbar interbody fusion (LLIF) using expandable cages. </sec><sec><title>Methods</title> A retrospective review was conducted on patients who underwent LLIF with expandable cages between May 2022 and May 2024. The study included 51 patients (28 men and 23 women; mean age: 70.6 ± 11.7 years). Surgical outcomes measured included SL, anterior DH, posterior DH, average DH, canal diameter, and central canal area (CCA). Pre- and postoperative measurements were compared to evaluate cage effectiveness. </sec><sec><title>Results</title> Postoperative measurements showed significant improvements: SL increased from 3.5° to 4.8° (<italic>P</italic> = 0.002), anterior DH from 5.9 to 10.7 mm (<italic>P</italic> < 0.001), PDH from 3.4 to 7.7 mm (<italic>P</italic> < 0.001), and average DH from 4.6 to 9.2 mm (<italic>P</italic> < 0.001). Despite these gains, the actual SL (4.8°) was significantly lower than the predicted SL (8.7°, <italic>P</italic> < 0.001). Canal dimensions also improved, with canal diameter increasing from 5.0 to 8.3 mm and CCA from 55.8 to 89.7 mm² (<italic>P</italic> < 0.001 for both). A significant correlation was found between changes in posterior DH and CCA (<italic>r</italic> = 0.272, <italic>P</italic> = 0.017). </sec><sec><title>Conclusion</title> Expandable cages in LLIF significantly improved DH, SL, and canal dimensions, contributing to better clinical outcomes. However, achieving the ideal SL remains challenging, highlighting the need for further refinement in surgical techniques and cage design. </sec><sec><title>Clinical Relevance</title> Expandable cages in LLIF significantly enhance DH, SL, and spinal canal dimensions, which contribute to improved clinical outcomes such as pain relief and functional recovery. However, the difficulty in achieving the ideal SL suggests further advancements are needed in surgical techniques and cage design to optimize patient outcomes and long-term spinal alignment. </sec><sec><title>Level of Evidence</title> 3. </sec>