Distribution of gender, age, clinical characteristics (coexistence of spondylolisthesis or scoliosis, severity of stenosis, and levels of decompression), and self-assessed satisfaction by the binary outcome of treatment (success or not, based on the JOA score; significant improvement of not, base on the ODI) will be tabulated. Fisher exact test will be preformed to compare the difference between the two groups. Odds ratios will be calculated by using the univariate logistic regression. Variables with two-sided p-value less than 0.05 were considered as significant factors associated with successful treatment. All statistical analyses are performed with statistical software, SAS version 9.1 (SAS Institute Inc, Cary, NC).