The test to retest reproducibility of walking test for intermittent claudication associated with lumbar spinal stenosis

Background The walking test is useful to evaluate leg numbness and pain caused by cauda equina symptoms in patients with lumbar spinal stenosis but there are few reports described about reproducibility. The study aim was to evaluate the reproducibility of the walking test for lumbar spinal stenosis Methods Seventy patients with lumbar spinal stenosis who had intermittent claudication symptoms at a multicenter outpatient clinic were examined prospectively. A walking test was performed at 0 and 4 weeks. We investigated walking distance and lower limb pain and numbness in this study. Pain and numbness were evaluated by using the Visual Analog Scale (VAS) immediately after the walking test for the hip and outside, inside, front, and posterior sides of the lower legs. Cohen’s kappa analysis and interphase correlation coefficients (ICCs) were used to evaluate reproducibility. The Swiss Spinal Stenosis Questionnaire (SSS) was used to evaluate stenosis severity. Results The mean SSS was 30.2 ± 5.5 initially and 29.2 ± 5.2 at week 4, with no significant difference in severity ( P = 0.10). The walking distance ICC between baseline and 4 weeks was 0.670. The interobserver reliabilities for lower limb ache and numbness in both legs were acceptable. The average VAS for lower leg pain was 23.2 ± 25.2 mm at baseline and 27.4 ± 28.8 mm at week 4. The ICC was 0.668. The average VAS for leg numbness was 23.4 ± 26.7 mm at baseline and 24.8 ± 25.2 mm at week 4. The ICC was 0.683. Conclusions The walking test walking distance and symptomatic site results were reproducible.


Background
Intermittent claudication is a major symptom of lumbar spinal stenosis (LSS) [1][2][3]. Increasing lumbar lordosis with standing and walking affects the circumference of cauda equina nerve and can cause ischemia. As a result, patients with LSS complain of pain or numbness of the legs. The walking test is used to assess lower limb symptoms during actual walking. The treadmill test [4], bicycle test [5], and stoop test [6] are also used to detect ischemia in cauda equina. On the contrary, few studies have compared the reproducibility of assessments of intermittent claudication. A previous investigation showed the superior reproducibility of the walking test for leg symptoms during walking compared with that of the treadmill test [7]. However, the walking test has some disadvantages. The walking test requires a huge space that is not required by other tests. Physicians cannot repeat this test easily, especially in an outpatient clinic. Therefore, the reproducibility of walking test results is important. However, reports on the reproducibility of the walking test are lacking. We therefore investigated the test-to-retest reproducibility of the walking test for intermittent claudication associated with LSS.

Study design
This was a multicenter analysis of patients with LSS. The study involved two types of patients with LSS: subjects who had not previously used any drugs and therapies for LSS, and subjects who had used some drugs and therapies for LSS before the study. All the subjects received vitamin B12 as treatment when the study began. For the subjects who had previously been treated for LSS, we preferred that they not continue receiving the original drugs and therapies during the study, but for those who chose to continue use, the original drugs or therapies, dosages, and frequency of drugs or treatment were not changed during the study. In addition, new drugs or therapies for LSS were forbidden. In total, 80 patients were recruited for the study. We enrolled patients who were diagnosed as having LSS and lumbar spondylolisthesis and had bilateral leg symptoms because of cauda equina.
The exclusion criteria were as follows: 1) positive results for straight-leg-raising test; 2) a past history of surgery for LSS; 3) lower leg numbness from cerebral palsy, brain infarctions, or diabetes mellitus neuropathy; 4) disease affecting gait (e.g., Parkinson disease), mental disease (e.g., depression); and 5) inability to understand this investigation.

Demographic Data Variables
We investigated the following demographic variables: age (defined as the duration from birth to informed consent rounded to the nearest year), sex, height (first observation value), weight (first observation value), disease duration, comorbidity, medical history, symptom assessment (pain or numbness), and walking distance.

Observation Variables
Subjects with LSS underwent the walking test performed according to the procedure detailed in a previous report [7]. The investigator walked in parallel with the subject away from the visual field without talking to the subject. Each subject continued walking until he or she became unable to walk because of pain or numbness of the lower extremities. We determined the walking distance and subjective symptoms (lower limb ache and numbness) in the walking test at baseline and at week 4.
We divided the lower leg into five parts as symptom areas: the front, back, outside, inside, and hips of the right and left legs (Fig. 1). The subjects were tested to determine in which parts of the lower leg pain or numbness was felt. We administered the Swiss Spinal Stenosis Questionnaire (SSS) at baseline and week 4 and compared both the baseline data and week 4 data to determine the reproducibility of the walking test results. Table 1 shows the schedule of this investigation

Statistical analysis
Three statistical tests were used to assess the test-to-retest reproducibility: The intraclass correlation coefficient (ICC) was used to measure interobserver agreement for walking distance to assess intermittent claudication. Cohen's kappa analysis was used to assess reproducibility of pain and numbness of the lower legs after walking. The chi-squared test was used to compare the changing severity assessed by the SSS over a 4-week period. The data analysis was performed using IBM SPSS Statistics software, Version 25.0 (IBM Corp., Armonk, NY, USA).

1) Subject enrollment and follow-up
A total of 80 subjects were recruited in this study. Of these subjects, 10 stopped participating after the baseline trial (one subject did not meet the inclusion criteria, one subject was not available, two subjects were lost to follow-up, and six subjects planned to stop participation before study completion). Finally, 70 patients were registered and investigated in this study. Table 2 summarizes the baseline characteristics.   (Table 3).

Discussion
Neurogenic intermittent claudication is caused by epidural pressure while walking [8]. Takahashi et al.
used an epidural transducer to investigate the epidural space pressure in patients with LSS. They concluded that epidural space pressure was higher in patients with LSS than in normal individuals and that it increased during walking [9]. Amundsen reported that 95 of 100 patients with LSS showed intermittent claudication, which is a major symptom of LSS [10]. We believe that it is highly important for physicians to check intermittent claudication associated with LSS to confirm the patients' symptoms. A limitation of this study was that we did not compare lower limb symptoms assessed by an imaging modality, such as magnetic resonance imaging, computed tomography, or X-ray radiography.

Conclusion
The walking test showed acceptable reproducibility of the walking distance and lower leg symptomatic sites.

Funding
This study was supported by ONO PHARMACEUTICAL CO., LTD.

Availability of data and materials
The datasets generated and analyzed during the current study are not publicly available due professional discretion, as they were part of patient's records, but are available as de-identified data sheet from the corresponding author on reasonable request.
Ethics approval and consent to participate This graph shows the magnitudes of lower limb numbness at baseline and week 4 using with Visual analog scale