Variability among methods and timing of pain assessment tools for tracking improvement of lumbar stenosis patients after surgery.

Background Context: Many different pain and functional outcomes are used to determine progress after surgical intervention for lumbar spinal stenosis (LSS); it is unknown how these different outcomes correlate, or whether timing of pain measurement is important.

Purpose: The goal was to determine whether method and timing of pain measurement is important in the context of LSS surgical outcomes.

Study Design/setting: Cohort study.

Patient Sample: LSS patients (N=21).

Outcome Measures: Self-report measures.

Methods: Each patient completed the 36-item Short Form, Oswestry Disability Index, and Swiss Spinal Stenosis Questionnaire 1 week presurgery and 6 months postsurgery. Objective function was measured using the Self-Paced Walking Test (SPWT). Low back and leg pain were assessed by visual analogue scale both immediately before the SPWT (prewalking pain) and at the symptom-limited endpoint (provoked pain). Pain was also assessed before and after surgery using the pain subscales of 36-item Short Form pain, Oswestry Disability Index, and Swiss Spinal Stenosis Questionnaire.

Results: Patients averaged 65.3 years of age with 15 being female. After surgery, all outcome measures improved significantly. Postwalking pain (provoked pain) demonstrating a strong relationship with objectively measured function (SPWT). Pain (visual analogue scale prewalk and postwalk) showed little correlation with reported changes in disability, general health or physical function.

Conclusions: Our results suggest that for patients with LSS, the context of the pain measurement matters, and it is important to measure pain after walking (provoked pain). Results also suggest that when examining the relationship between pain and function, objective measures of function are preferable (eg, a walking test). Finally, given the lack of association between measures of pain, it is important to understand that each pain measure is addressing a different pain construct. Therefore, when conducting outcomes studies, it is imperative to compare the exact same pain measures across time points.