Inclusion Criteria:  1. Patients should be diagnosed as CSM based on the history, symptoms, Physical signs and radiographic results. 2. Patients did not respond to the 3-month conventional treatment. 3. Patients were performed posterior approach of cervical spine operation. 4. Patients should have complete pre- and post-operative data.  Exclusion Criteria:  1. Patients with severe organic diseases. 2. Patients with previous history of cervical spine surgery. 3. Patients with mental or psychological abnormality. 4. Patients with severe osteoporosis (T value <-2.5).