Accuracy and reproducibility of a retrospective outcome assessment for lumbar spinal stenosis surgery

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.

Preoperative MRI findings predict two-year postoperative clinical outcome in lumbar spinal stenosis

PURPOSE

To study the predictive value of preoperative magnetic resonance imaging (MRI) findings for the two-year postoperative clinical outcome in lumbar spinal stenosis (LSS).

METHODS

84 patients (mean age 63±11 years, male 43%) with symptoms severe enough to indicate LSS surgery were included in this prospective observational single-center study. Preoperative MRI of the lumbar spine was performed with a 1.5-T unit. The imaging protocol conformed to the requirements of the American College of Radiology for the performance of MRI of the adult spine. Visual and quantitative assessment of MRI was performed by one experienced neuroradiologist. At the two-year postoperative follow-up, functional ability was assessed with the Oswestry Disability Index (ODI 0-100%) and treadmill test (0-1000 m), pain symptoms with the overall Visual Analogue Scale (VAS 0-100 mm), and specific low back pain (LBP) and specific leg pain (LP) separately with a numeric rating scale from 0-10 (NRS-11). Satisfaction with the surgical outcome was also assessed.

RESULTS

Preoperative severe central stenosis predicted postoperatively lower LP, LBP, and VAS when compared in patients with moderate central stenosis (p<0.05). Moreover, severe stenosis predicted higher postoperative satisfaction (p = 0.029). Preoperative scoliosis predicted an impaired outcome in the ODI (p = 0.031) and lowered the walking distance in the treadmill test (p = 0.001). The preoperative finding of only one stenotic level in visual assessment predicted less postoperative LBP when compared with patients having 2 or more stenotic levels (p = 0.026). No significant differences were detected between quantitative measurements and the patient outcome.

CONCLUSIONS

Routine preoperative lumbar spine MRI can predict the patient outcome in a two-year follow up in patients with LSS surgery. Severe central stenosis and one-level central stenosis are predictors of good outcome. Preoperative finding of scoliosis may indicate worse functional ability.