Inclusion Criteria:  Age between 20 and 80 years Indicated of elective spine fusion surgery for spinal stenosis or degenerative spondylolisthesis at the study hospital from January 2016 to December 2017.  Exclusion Criteria:  Spinal instability due to trauma, infection, or malignancy History of previous spine surgery Hemodialysis Long-term steroid use History of medical treatments for osteoporosis Postoperative follow-up for less than 12 months Newly-onset compression fracture after study procedure