Step activity monitoring in lumbar stenosis patients undergoing decompressive surgery

Abstract

Symptomatic degenerative central lumbar spinal stenosis (LSS) is a frequent indication for decompressive spinal surgery, to reduce spinal claudication. No data are as yet available on the effect of surgery on the level of activity measured with objective long-term monitoring. The aim of this prospective, controlled study was to objectively quantify the level of activity in central LSS patients before and after surgery, using a continuous measurement device. The objective data were correlated with subjective clinical results and the radiographic degree of stenosis. Forty-seven patients with central LSS and typical spinal claudication scheduled for surgery were included. The level of activity (number of gait cycles) was quantified for 7 consecutive days using the StepWatch Activity Monitor (SAM). Visual analogue scales (VAS) for back and leg pain, Oswestry disability index and Roland-Morris score were used to assess the patients' clinical status. The patients were investigated before surgery and 3 and 12 months after surgery. In addition, the radiographic extent of central LSS was measured digitally on preoperative magnetic resonance imaging or computed tomography. The following results were found preoperatively: 3,578 gait cycles/day, VAS for back pain 5.7 and for leg pain 6.5. Three months after surgery, the patients showed improvement: 4,145 gait cycles/day, VAS for back pain 4.0 and for leg pain 3.0. Twelve months after surgery, the improvement continued: 4,335 gait cycles/day, VAS for back pain 4.1 and for leg pain 3.3. The clinical results and SAM results showed significant improvement when preoperative data were compared with data 3 and 12 months after surgery. The results 12 months after surgery did not differ significantly from those 3 months after surgery. The level of activity correlated significantly with the degree of leg pain. The mean cross-sectional area of the spinal canal at the central LSS was 94 mm(2). The radiographic results did not correlate either with objective SAM results or with clinical outcome parameters. In conclusion, this study is the first to present objective data on continuous activity monitoring/measurements in patients with central LSS. The SAM could be an adequate tool for performing these measurements in spine patients. Except for leg pain, the objective SAM results did not correlate with the clinical results or with the radiographic extent of central LSS.

Figures

Fig. 1

The StepWatch 3 Activity Monitor (SAM)

Fig. 2

Axial view of the spinal canal. a Thickness of the right yellow ligament. b Thickness of the left yellow ligament. c Maximum sagittal diameter; dark grey: cross-sectional area of the spinal canal

Fig. 3

Example of a StepWatch 3 Activity Monitor (SAM) measurement over 24 h in a selected patient. Top the situation before surgery, with 2,856 gait cycles per day. Bottom the situation 3 months after decompression, with 5,339 gait cycles per day

Fig. 4

Gait cycles per day (mean, standard deviation). n.s. not significant, FU follow-up, Mo months

Fig. 5

Relative changes (percentage improvements in means) in objective gait cycles per day, compared with the relative changes in subjective clinical results. FU follow-up, Mo months, VAS visual analogue scale, ODI Oswestry disability index, RMS Roland–Morris score