From Oswestry to LMDA-6: Feasibility and Validation of a Six-Item Lumbar Disability Questionnaire in a Tertiary Neurosurgical Center

Functional disability assessment is crucial for lumbar spine disease management, but standard instruments like the Oswestry Disability Index (ODI) are often too lengthy for high-volume tertiary practice. We evaluated the feasibility and psychometric properties of the Lumbar Mobility Disability Assessment-6 (LMDA-6), a brief Oswestry-aligned questionnaire. Fifty adult patients with degenerative low back pain were randomly selected from a tertiary neurosurgical electronic-PROM program to complete the baseline ODI and LMDA-6. The LMDA-6 (6 items, scored 0–100%) was administered twice in one session to assess short-interval test–retest reliability. LMDA-6 was scorable in all 50 patients with minimal floor (3.7%) and ceiling (1.9%) effects (mean 49.6±24.8). Internal consistency was excellent (Cronbach’s α 0.93–0.94); principal component analysis supported unidimensionality (first component 75–78% variance). Test–retest reliability was very high (ICC[A,1]=0.985; mean difference −0.52; SEM 3.12; MDC 95 8.63; equivalence within ±5 points). Convergent validity with ODI was moderate-to-strong (r=0.651), with stepwise increases in LMDA-6 across ODI severity bands and good discrimination of severe ODI (≥40%; AUC=0.859). With pre-specified ODI-aligned severity bands, quadratic-weighted κ was 0.40 (exact agreement 24%; within-one-category 68%; accuracy for ODI≥40% 0.70, sensitivity 0.68, specificity 1.00). Optimized LMDA-6 cut-points improved κ to 0.74 (exact 58%; within-one 98%) in this exploratory sample. The LMDA-6 is a feasible, highly reliable, and Oswestry-aligned measure suitable for routine use in high-volume neurosurgical outpatient settings. It provides a pragmatic alternative to the full ODI for longitudinal monitoring, though optimized severity thresholds require confirmation in larger cohorts. • LMDA-6 offers a brief, valid alternative to the Oswestry Disability Index. • Test–retest reliability is outstanding (ICC=0.99) in routine spine care. • Optimized cut-points show strong agreement (κ=0.74) with ODI severity.