Minimal Clinically Important Difference in the Six-Minute Walking Distance 12 Months After Lumbar Spinal Stenosis Surgery.

STUDY DESIGN

This was a prospective single-center study.

PURPOSE

This study aimed to calculate the minimal clinically important difference (MCID) of the six-minute walk distance (6MWD) postoperatively. Overview of the literature: The 6MWD and Zurich Claudication Questionnaire (ZCQ) have recently been used to evaluate the intermittent claudication of lumbar spinal stenosis (LSS). However, there is no report concerning the MCID of postoperative changes of 6MWD in patients with LSS.

METHODS

This prospective study included patients aged 60 or older who underwent surgery for LSS with intermittent claudication as the primary symptom at a single institution from 2022 to 2024. The 6MWD and the ZCQ were assessed preoperatively and 12 months postoperatively. The MCID was evaluated using an anchor-based approach using ZCQ. The Spearman's rank correlation coefficient was used to determine the correlation between the pre-and postoperative changes in 6MWD and ZCQ. The MCID was calculated using the receiver operating characteristic (ROC) curve. Calculated MCID and area under the curve (AUC) were evaluated by internal validation using the bootstrap method. A significance level of <0.05 was used, and bootstrap validation was performed with a 95% confidence interval.

RESULTS

One hundred and five patients were included in the study. The average preoperative and postoperative 6MWD were 282 meters and 385 meters, respectively (p<0.01). The ZCQ significantly improved from 2.64 to 1.73 postoperatively (p<0.01). Postoperative 6MWD and ZCQ correlated substantially with change (r=-0.58, p<0.01). In the anchor-based approach, 67 patients (63%) responded to the anchor ZCQ with an MCID of 80.0 m. This MCID had a sensitivity of 92.1%, a specificity of 76.1%, and an AUC of 90.6%, which was excellent. Internal validation showed moderate to excellent reliability with 95% confidence intervals for MCID and AUC ranging from 40 m to 100 m and 86% to 95%, respectively.

CONCLUSIONS

In this study, the MCID of postoperative changes of the 6MWD in patients with LSS was 80 m. This value helps evaluate the surgical results of patients with LSS.