Evolution of Alignment and Clinical Outcomes During One Surgeon’s Learning Curve in L5-S1 Anterior Lumbar Interbody Fusion: A Single-Center Experience

<b>Background:</b> Anterior Lumbar Interbody and Fusion (ALIF) is particularly effective for improving radiographic alignment and functional outcomes. However, it also introduces distinct technical challenges, even for surgeons who are highly experienced with other lumbar fusion approaches. This study analyzes the effect of surgeon experience on clinical outcomes, radiographic parameters, and operative metrics in patients with degenerative lumbar disc disease undergoing single-level L5-S1 anterior lumbar interbody fusion. <b>Methods:</b> Adult patients who underwent L5-S1 ALIF with or without posterior fixation for degenerative disc disease between June 2017 and December 2024 were included. Patients were stratified into Early (from 2017 to December 2020), Middle (January 2021 to December 2022), and Recent (January 2023 to December 2024) groups. Demographics, radiographic alignment, in-hospital outcomes, and 2-year complication and reoperation rates were compared based on time of surgery. Multivariate logistic and linear regression adjusted for age, sex, BMI, comorbidities, prior fusion, and posterior instrumentation was conducted to assess the effect of accumulation of surgeon experience. <b>Results:</b> A total of 203 ALIFs were performed (mean age: 57.6 years; 50.7% female; mean Charlson Comorbidity Index: 2.1). Recent cases showed greater PT reduction (Early = 0.9°, Middle = -1.5°, Recent = -2.2°, <i>p</i> = 0.039), improved PI-LL mismatch correction (-0.4°, -4.8°, -5.4°, <i>p</i> = 0.007), higher L5-S1 lordotic correction (6.7°, 8.4°, 11.4°, <i>p</i> = 0.003), lower estimated blood loss (21.9 mL, 13.8 mL, 10.0 mL, <i>p</i> = 0.006), shorter OR time (107.4 min, 86.6 min, 75.2 min, <i>p</i> < 0.001), and fewer mechanical complications (39.3% vs. 13.7%, <i>p</i> < 0.001) and reoperations (10.7% vs. 2.1%, <i>p</i> = 0.023). Regression showed that each additional year of experience predicted improved alignment, lower blood loss and OR time, and reduced odds of complications (OR = 0.54, <i>p</i> < 0.001) and reoperations (OR = 0.49, <i>p</i> = 0.015). <b>Conclusions:</b> In this single-surgeon, single-center cohort, increasing ALIF-specific experience over time was associated with improvements in sagittal alignment, operative efficiency, and lower complication and reoperation rates. These findings describe the longitudinal learning curve of one surgeon and should be interpreted within this context.