Minimal clinically important difference of the 6-Minute walk test and daily step count at 3 months following surgery for lumbar spinal stenosis.

PURPOSE

This study aimed to estimate the minimal clinically important difference (MCID) in two objective measures of walking: 6-minute walk distance (6MWD) and mean daily step count in patients with lumbar spinal stenosis, three months post-surgery. Both anchor-based and distribution-based approaches were used to support result robustness and comparability.

METHODS

97 patients (mean age 70 ± 8.3 years; 50 female) were recruited from three UK hospitals. 6MWD (metres) and mean daily step count (measured over 7 days with an accelerometer), and self-rated clinical questionnaires were assessed pre- and 12-weeks post-surgery. The anchor-based method used the Oswestry Disability Index (ODI) and the satisfaction subscale of the Zurich Claudication Questionnaire. Receiver-operating characteristic (ROC) curve analysis was used to determine the optimal cutoff points for MCIDs for changes in the 6MWD and step count. The distribution-based method used 0.3 SD of the change scores.

RESULTS

Anchor-based MCIDs for the 6MWD were 26 m (ODI) and 35 m (walking satisfaction). The step count MCID could not be determined using the ODI but was 680 steps when anchored to satisfaction. The distribution-based method estimated MCIDs of 34 m for the 6MWD and 750 steps for step count.

CONCLUSION

Even modest improvements in walking capacity and daily step count may be meaningful to patients recovering from LSS surgery. Further research is needed to validate the MCID for daily step count however, the identified MCIDs for the 6MWD (26-35 m) and daily step count (680-750 steps) provide practical thresholds for assessing meaningful change and can be used to inform goal setting within rehabilitation.