Responsiveness of the Oswestry Disability Index in Symptomatic Lumbar Spondylolisthesis.

BACKGROUND AND OBJECTIVE: The Oswestry Disability Index (ODI) is one of the most widely used questionnaires measuring Low Back Pain-related disability. The responsiveness of the ODI Italian version (ODI-I) was investigated in subjects complaining of non-specific LBP, however to date no study was made on other clinical conditions. This study aimed to investigate the responsiveness and the minimum important change of the ODI-I in subjects with lumbar spondylolisthesis (SPL). MATERIALS AND METHODS: 151 patients with symptomatic SPL completed the ODI-I, the 0–100 Numerical Rating Scale (NRS), and performed the Prone and the Supine Bridge Tests to measure lumbar muscles endurance, pre- and post-treatment. The global perception of effectiveness was measured with a 7-point Likert scale. Responsiveness was assessed by distribution methods [Minimum Detectable Change (MDC); Effect Size (ES); Standardized Response Mean (SRM)] and anchor-based methods (ROC curves). RESULTS: The mean number of sessions was 8 ±2 and the mean duration of the treatment was 2 ±1 months. The main ODI score pre-treatment was 22.8 ±12.9 and the main post-treatment change was -10.7 ±0.9. All other outcome measures (NRS, PBT, and SBT) showed statistically significant improvements after the period of treatment. The MDC was 4.23; the ES was 0.95 and the SRM was 1.25; ROC analysis revealed an area under the curve of 0.76 thus indicating moderate discriminating capacity; the best cut-off point for the dichotomous outcome was 7.5 (sensitivity 90.3% and specificity 56.7%). DISCUSSION: The main ODI-I score and the main post-treatment changes were similar with those calculated in another study on SPL subjects; the changes in ODI-I scores are in line with the minimum important change proposed in literature (a reduction of 10 points, or a decrease of 30% compared to baseline). The changes in ODI-I score appeared also significantly related to the amount of perceived improvement and were coherent with the changes in the other outcome measures, concerning lumbar pain and muscular endurance. CONCLUSIONS: Our results showed a relevant and comparable effect of the treatment on the ODI-I score. The ODI-I proved to be responsive in detecting changes after physical therapy treatment in subjects with lumbar SPL.