The Efficacy of Prone Single-Position Lateral Lumbar Interbody Fusion for Symptomatic Cranial Adjacent Segment Degeneration

<b>Background/Objectives</b>: Following lumbar fusion procedures, adjacent segment degeneration (ASD) at cranial levels presents as a well-documented long-term complication, manifesting through recurrent pain, neurological deficits, and progressive functional decline. The prone single-position technique for lateral lumbar interbody fusion (PSP-LLIF) streamlines surgical workflow by eliminating the need for intraoperative patient repositioning; however, comprehensive evidence supporting its clinical and radiological effectiveness in managing cranial ASD remains insufficient. <b>Material and Methods</b>: This retrospective cohort study examined 30 consecutive patients presenting with symptomatic cranial adjacent segment disease who were treated with PSP-LLIF at a single institution. Patient-reported outcome measures included visual analog scale (VAS) assessments for axial and radicular pain, alongside the Oswestry Disability Index (ODI) for functional status evaluation. Radiological parameters included overall and segmental lumbar lordotic measurements, anterior and posterior disk height, fusion status, and instrumentation-related complications. <b>Results:</b> At 12-month postoperative evaluation, substantial clinical improvements were demonstrated. Mean VAS reductions measured 4.7 points for axial pain and 6.5 points for radicular pain, while ODI decreased by 28.5 points (<i>p</i> < 0.05). Radiological assessment demonstrated mean increases of 6.3° in lumbar lordosis and 5.1° in segmental lordosis, along with significant gains in both anterior and posterior disk height (<i>p</i> < 0.05). Solid fusion was radiographically confirmed at all instrumented levels. Temporary postoperative neurological symptoms developed in several patients but resolved spontaneously without requiring revision surgery. <b>Conclusions:</b> PSP-LLIF yields substantial clinical benefit and reliable radiological correction in patients with symptomatic cranial ASD. Optimal outcomes necessitate rigorous adherence to position-specific technical modifications, particularly maintenance of perpendicular fluoroscopic trajectories and implementation of continuous neural monitoring to account for prone-induced anatomical shifts. This approach represents a viable treatment strategy for patients with symptomatic cranial ASD.