Does Restoration of Lumbar and Segmental Cobb Angle Affect Fusion Outcome in Short-Segment Posterior Lumbar Fusion?

Objective: To study the effect of lumbar lordosis change and pelvic parameters on surgical outcomes such as fusion versus nonfusion (pseudarthrosis), adjacent segment pathology (ASP), and reoperation in patients undergoing 1-level, 2-level, and 3-level posterior lumbar fusion (PLF). Methods: Adult patients with degenerative spine disease who had undergone PLF between L2 and L5 levels at an academic center between 2010 and 2020 were included. Preoperative and early postoperative lateral standing radiographs of the lumbar spine were used to measure preoperative lumbar Cobb angle, postoperative lumbar Cobb angle, preoperative segmental Cobb angle (measured from the superior end plate of the upper instrumented vertebra to the inferior end plate of the lower instrumented vertebra), postoperative segmental Cobb angle, preoperative pelvic incidence, and pelvic tilt. Change in lumbar and segmental Cobb angle was calculated as postoperative Cobb angle (lumbar and segmental) minus preoperative Cobb angle. Results: A total of 243 patients met our inclusion and exclusion criteria. Patients who had pseudarthrosis had significantly less restoration of lumbar lordosis compared with those who did not, both for lumbar Cobb angle change (–5.2 ± 8.2 vs. –0.2 ± 8.2; P = 0.01) and segmental Cobb angle change (–5.4 ± 6.6 vs. –1.5 ± 6.0; P = 0.01). Moreover, pelvic incidence was lower in patients who developed ASP versus those who did not. There was no significant difference in these measures (lumbar Cobb angle changes and segmental Cobb angle change) in patients who experienced ASP and those who did not. Conclusions: Better restoration of lumbar lordosis reduces rates of pseudarthrosis after short-segment PLF but has no association with rates of ASP.