Distance to first symptoms measured by the 6-min walking test differentiates between treatment success and failure in patients with degenerative lumbar disorders

Abstract

Purpose The smartphone-based 6-min walking test (6WT) is an established digital outcome measure in patients undergoing surgery for degenerative lumbar disorders (DLD). In addition to the 6WTs primary outcome measure, the 6-min walking distance (6WD), the patient’s distance to first symptoms (DTFS) and time to first symptoms (TTFS) can be recorded. This is the first study to analyse the psychometric properties of the DTFS and TTFS. Methods Forty-nine consecutive patients (55 ± 15.8 years) completed the 6WT pre- and 6 weeks (W6) postoperative. DTFS and TTFS were assessed for reliability and content validity using disease-specific patient-reported outcome measures. The Zurich Claudication Questionnaire patient satisfaction subscale was used as external criterion for treatment success. Internal and external responsiveness for both measures at W6 was evaluated. Results There was a significant improvement in DTFS and TTFS from baseline to W6 (p < 0.001). Both measures demonstrated a good test–retest reliability (β = 0.86, 95% CI 0.81–0.90 and β = 0.83, 95% CI 0.76–0.87, both p < 0.001). The DTFS exceeded the 6WD capability to differentiate between satisfied (82%) and unsatisfied patients (18%) with an AUC of 0.75 (95% CI 0.53–0.98) vs. 0.70 (95% CI 0.52–0.90). The TTFS did not demonstrate meaningful discriminative abilities. Conclusion Change in DTFS can differentiate between satisfied and unsatisfied patients after spine surgery. Digital outcome measures on the 6WT metric provide spine surgeons and researchers with a mean to assess their patient’s functional disability and response to surgical treatment in DLD.

Digital Biomarkers and the Evolution of Spine Care Outcomes Measures: Smartphones and Wearables

“…19,23,[41][42][43][44][45] Smartphone administration of these assessments could allow for more frequent testing and a reduction of Hawthorne effects. Zeitlberger et al 46 examined more granular measures of a smartphone app-based 6WT in patients with degenerative lumbar disorders. They found that the time to first symptoms (TTFS) and distance to first symptoms (DTFS) improved from baseline at 6 weeks postoperatively and that DTFS was better able to differentiate between satisfied and unsatisfied patients than 6WT alone.…”

“…Ahmad et al 49 examined smartphone mobility data during a two-year perioperative period in patients who underwent elective lumbar decompressive surgery. They describe 5 clinical stages characterized by mobility patterns: preoperative baseline, preoperative presentation/ decline, immediate postoperative recovery, full recovery, and possible 49 Ahmad 2021 50 Basil 2021 3 Boaro 2021 26 Cote 2019 22 Maldaner 2021 41 Zaldivar-Jolissaint 2021 51 Zeitlberger 2022 46 Zeitlberger 2021 42 Postoperative secondary decline. These stages correlated with clinical documentation of the patients' courses.…”

“…Patients in the DCP group had high engagement and a reduction in their ODI, as well as a 52% decrease in average interest in surgery vs the control group, who showed a 53% increase in average interest in surgery. Intriguingly, this suggests that digital interventions could play a future role in managing patient treatment 41 Maldaner 2020 19 Sosnova 2020 44 Zeitlberger 2022 46 Zeitlberger 2021 42 Zeitlberger 2020 43 DDD Neurogenic claudication and/or radiculopathy 6WT (OFI), TUG (OFI)…”