Predictors of walking ability after surgery for lumbar spinal canal stenosis: a prospective study.

Abstract

Few studies have investigated predictors of objective walking distance in patients with lumbar spinal stenosis (LSS). This study aimed to clarify objective predictors of postoperative 6-minute walk distance (6MWD) in patients with LSS and to develop prediction equations. This was a prospective study. Data were analyzed by multiple linear regression analyses. Patients with LSS were enrolled. Predictors of 6MWD after surgery were evaluated, including patient characteristics (sex, age, height, and body weight), pain (visual analog scale; low back pain, lower limb pain, and lower limb numbness), surgical factors (number of operation segments [1 or ≥2], surgery type [fusion or decompression], and minimum area of the dural sac), and objective physical function (6MWD and trunk muscle strength). Patients with LSS were consecutively included and assessed preoperatively (n=113) and 6 months postoperatively (n=78). Simple and multiple linear regression analyses were performed with 6MWD at 6 months postoperation as the dependent variable. We have study funding sources (Nagono Medical Foundation) and no study-specific conflicts of interest-associated biases. At 6-month follow-up, 6MWD (457.7±105.5 m) improved significantly compared with preoperative 6MWD (275.0±157.2 m; p<.01). Trunk muscle strength and pain improved significantly compared with the preoperative score (p<.01). The predictors of postoperative 6MWD were age, body weight, number of operation segments (1 or ≥2), surgery type (fusion or decompression), preoperative trunk extensor strength, and preoperative 6MWD (adjusted R²=0.65, p<.01). The proposed prediction equation was as follows: postoperative 6MWD (m)=549.5-5.3×age (years)-1.8×body weight (kg)-68.3×surgery type (0: decompression, 1: fusion)-58.6×operation segment (0: one segment, 1: ≥2 segments)+3.5×trunk extensor strength (kg)+0.2×preoperative 6MWD (m). Younger age, lower body weight, one level operative segment, decompression surgery, and better preoperative scores for trunk extensor strength and 6MWD predicted better scores for 6 months postoperative 6MWD. Preoperative reduction in body weight and increase of trunk extensor strength might be associated with improved postoperative 6MWD scores.