Multilevel Lateral Lumbar Interbody Fusion for Symptomatic Spondylotic Stenosis and Severe Disc Degeneration Without Scoliosis: Single-Institutional Case Series and Lessons Learned

<sec><title>Background</title> Posterior decompression for degenerative lumbar spinal stenosis (DLSS) carries approach-related morbidity. In this study, we hypothesized that multilevel lateral lumbar interbody fusion (LLIF) achieves effective indirect decompression with acceptable safety and patient-reported improvement among DLSS patients without scoliosis. </sec><sec><title>Methods</title> This was a single-institution retrospective case series (2016–2022) of adults with symptomatic spondylotic stenosis and severe disc degeneration without scoliosis (Cobb angle <10°) undergoing multilevel (≥2) LLIF. Patients with concurrent posterior decompression or deformity correction were excluded. Primary outcomes were radiographic decompression (central canal diameter and bilateral foraminal height), patient-reported pain and disability (visual analog scale and Oswestry Disability Index), and complications. Secondary measures included spinopelvic parameters and fusion by the Brantigan-Steffee-Fraser scale. Imaging was assessed on pre- and postoperative magnetic resonance imaging. Tests of significance included 1-sided paired <italic>t</italic> tests for parametric variables and Wilcoxon signed-rank tests otherwise. </sec><sec><title>Results</title> Twenty-five patients (mean age 65.8 years; 56% men; mean body mass index 31.2 ± 5.4) underwent 57 LLIF levels with a mean follow-up of 41.3 ± 31.6 months. Central canal diameter increased by 31% (2.2 mm absolute), and foraminal height increased 17% to 39% (2.5–13.1 mm). Lumbar lordosis improved from 39.6° to 44.8°, with PI–LL mismatch improving by 5.4°. Early fusion status (BSF-3) at the last radiological assessment (mean 7.2 months) was 91.3% (21/23 evaluated). Visual analog scale score improved from 7.1 ± 2.0 to 3.0 ± 2.4 (Δ−4.1; <italic>n</italic> = 20), and Oswestry Disability Index score improved from 65.9 ± 12.9 to 47.5 ± 19.8 (Δ−18.4; <italic>n</italic> = 17). Overall complication rate was 40% with no major events; postoperative neurological complications included transient proximal lower-extremity weakness in 4% and persistent sensory symptoms in 12%. </sec><sec><title>Conclusions</title> In carefully selected DLSS patients without scoliosis, multilevel LLIF achieved meaningful indirect decompression, substantial pain and disability improvement, and high early fusion rates with no major complications. The findings support LLIF as a viable alternative to posterior approaches. </sec><sec><title>Clinical Relevance</title> Multilevel LLIF can facilitate multilevel indirect decompression with favorable radiographic and clinical outcomes while avoiding posterior soft-tissue disruption. Routine posterior instrumentation at the index surgery may support fusion and reduce returns to the OR. </sec><sec><title>Level of Evidence</title> 4. </sec>