Association of operative-level segmental lordosis correction with reciprocal changes in sagittal and spinopelvic parameters after single-level lateral lumbar interbody fusion at L4-5.

PURPOSE: Assess the relationship between change in L4-5 segmental lordosis (SL) and its effect on clinical and radiographic parameters after lateral lumbar interbody fusion (LLIF) at L4-5.

METHODS

Clinical scores and radiographic measurements were collected for patients who underwent single-level LLIF at L4-5 at a local institution between 2017 and 2022. Linear regression analysis was performed for changes in clinical and radiographic parameters as a function of change in SL.

RESULTS

Ninety-four patients were included in the analysis. Significant preoperative to postoperative increases occurred in L4-5 SL (P < 0.001), L2-3 SL (P = 0.04), anterior disc height (P < 0.001), posterior disc height (P < 0.001), neural foraminal height (P < 0.001), and T1-pelvic angle (P = 0.03). Significant decreases occurred postoperatively in L5-S1 SL (P < 0.001) and spondylolisthesis length (P < 0.001). Change in L4-5 SL was positively correlated with Δ lumbar lordosis (LL; P = 0.001), Δ distal LL (P < 0.001), Δ anterior disc height (P < 0.001), and Δ T5-T12 kyphosis (P = 0.04). Change in L4-5 SL was negatively correlated with Δ pelvic incidence-LL mismatch (P = 0.001) and Δ L5-S1 SL (P = 0.01).

CONCLUSION

LLIF at L4-5 induced greater L4-5 SL; this change was positively associated with changes in LL, distal LL, anterior disc height, and T5-T12 kyphosis, and negatively associated with changes in pelvic incidence-LL mismatch and L5-S1 SL. Potential compensatory changes proximal and distal to the LLIF level may depend on the amount of SL achieved at the operative level.