Sagittal Alignment Correction and the Extent of Intervertebral Distraction as Factors Associated with Postoperative Radiculitis Following Anterior Lumbar Interbody Fusion

Background/Objectives: To investigate the prevalence and associated factors of postoperative radiculitis in patients treated with Anterior Lumbar Interbody Fusion (ALIF) in L4–L5 or L5–S1 utilizing lumbopelvic sagittal parameters and ideal alignment values calculated with GAP score components. Methods: A retrospective review using Natural Language Processing (NLP) for automated data extraction from clinical notes was conducted. 61 adult patients were included in the analysis. Postoperative radiculitis was defined as the new onset of unilateral or bilateral pain in the L4–S1 radicular territory with preserved motor function. Clinical parameters (Oswestry Disability Index), radiographic parameters (lumbopelvic sagittal alignment using GAP score components), and surgical factors (cage size and disc height modification) were evaluated and subsequently entered into a multivariable logistic regression analysis. Results: Postoperative radiculitis occurred in 29.5% of patients, with symptoms primarily manifesting within the first six weeks following surgery and lasting up to six months. Patients in the Pain group showed notable differences in pre- and postoperative GAP score parameters, specifically higher values for relative lumbar lordosis (RLL) and relative pelvic version (RPV). Furthermore, multivariable logistic regression identified postoperative RLL and the anterior disc height (ADH) ratio to be independently associated with the development of radiculitis. Conclusions: Excessive disc space enlargement during ALIF is associated with a higher likelihood of postoperative radiculitis, particularly in patients with pre-existing near-ideal lumbar alignment. To mitigate this iatrogenic complication in this group, the degree of correction must be individualized. This tailored approach should incorporate parameters from the GAP score and a careful assessment of the relationship between the anterior disc height and the vertebral body.