Impact of Pain on Lumbar Spine Functional Assessment: Are Sufficient Flexion and Extension Achieved?

Abstract

There is currently no universally accepted standard for evaluating lumbar spinal instability, and assessment criteria vary across institutions, potentially leading to inconsistent decision-making when choosing between decompression alone and decompression with fusion. To address the need for consistent and reproducible functional radiographs, we investigated the influence of pain on lumbar motion during functional radiography. We prospectively analyzed patients with lumbar degenerative spondylolisthesis who underwent both conventional flexion (CF) and hands-on-knees (HK) flexion-extension radiography between January 2022 and February 2025. The HK method provides a clear endpoint by having patients place their hands on their knees, enabling deeper flexion. Clinical assessments before imaging involved the Oswestry Disability Index, Roland-Morris Disability Questionnaire, and Visual Analog Scale for low back and leg pain. The changes in lumbar lordosis during flexion [ΔLL(flex)] and extension were calculated and correlated with clinical scores. Sagittal translation was measured in CF and HK flexion-extension radiographs and compared between methods. Among 150 patients (103 females; mean age, 76.0 years), the median ΔLL(flex) was 10.8° with CF and 30.0° with HK (P<0.001). ΔLL(flex) was negatively correlated with the Oswestry Disability Index, Roland-Morris Disability Questionnaire, and Visual Analog Scale scores in CF (all P<0.01), but not in HK. The changes in lumbar lordosis during extension showed no significant correlations. Sagittal translation was significantly greater in HK than in CF. Both intrarater and inter-rater reliability were good. Pain may limit flexion during conventional radiography, potentially underestimating instability. The HK method may help establish objective criteria and surgical planning through improved reproducibility.