Background: Dr. Shi recently proposed a new technique as Ossification of anterior decompression surgery, which is also called anterior controllable antedisplacement and fusion (ACAF) , for ossification of the posterior longitudinal ligament (OPLL) and cervical canal stenosis（CSS）. Yet, the effectiveness and safety should be further studied.

Purpose: The aim of this study is to compare the effectiveness of clinical outcomes between ACAF surgery and Anterior cervical corpectomy decompression and fusion（ACCF）in patients with OPLL and CSS . A study hypothesis is that ACAF surgery outcomes will be equal even better and lower surgical complications which compared to ACCF surgery.

Methods: This study is a randomized clinical trial with randomized, controlled, multicenter research design. The OPLL patients will be randomly assigned in one of the two treatment groups: ACAF surgery and ACCF surgery. Five outcome measures will be collected pre-operative for baseline, and then at1, 12, 24, 48, 96,240weeks post-operative follow-up visits, including: (1)JOA) .(2)VAS. (3)NURIC Graded .(4)NDI . (5) radiological parameter. After randomization, the ACAF group will receive anterior controllable antedisplacement and fusion and the ACCF group will receive anterior cervical corpectomy decompression and fusion.

Background: Although anterior and posterior decompression surgery are both reported to treat patients with myelopathy caused by OPLL（Posterior longitudinal ligament ossification）. The surgical strategy of the disease is still controversial when the OPLL is multilevel and severe. Novel techniques for better and safer results are required. Dr. Shi recently proposed a new technique as Ossification of anterior decompression surgery, which is also called anterior controllable antedisplacement and fusion (ACAF) , for ossification of the posterior longitudinal ligament (OPLL) with myelopathy. Yet, the effectiveness and safety should be further studied.

Purpose: The aim of this study is to compare the effectiveness and safety of clinical outcomes between ACAF surgery and Anterior cervical corpectomy decompression and fusion（ACCF）in patients with OPLL. A study hypothesis is that ACAF surgery outcomes will be equal even better and lower surgical complications which compared to ACCF surgery.

Methods: This study is a randomized clinical trial with randomized, controlled, multicenter research design. The OPLL patients will be randomly assigned in one of the two treatment groups: ACAF surgery and ACCF surgery. Five outcome measures will be collected pre-operative for baseline, and then at1, 12, 24, 48, 96,240weeks post-operative follow-up visits, including : (1) Japanese Orthopaedic Association (JOA) scales to assess the spinal cord functions.(2)Visual analogue scale (VAS) to assess pain relief. (3)NURIC Graded to assess walking function.(4) Neck Disabilitv Index(NDI) to assess cervical function . (5) radiological parameters to assess ossification forward distance. And the pre & postoperative radiological parameters, and surgical complications were also investigated. The investigator performing the outcome measures will be blinded to group assignment, and therefore will not participate in treatment. After randomization, the ACAF group will receive anterior controllable antedisplacement and fusion and the ACCF group will receive anterior cervical corpectomy decompression and fusion.

Data Analysis: T test or wilcoxon rank sum test will be used to examine the differences in the five measures between groups and at the six different time frames with the α level set at 0.05. Chi square test will be used to compare the differences in the surgical complications data over time and between groups.

Inclusion Criteria:

1. patients aged 45-70 years, without gender limitation, are willing to sign informed consent;
2. patients diagnosed with posterior longitudinal ligament ossification of the cervical spine;
3. patients with limbs numbness, walking instability, banding and other spinal cord, nerve root compression symptoms, may be associated with urinary dysfunction, conservative treatment is invalid or gradually increased;

Exclusion Criteria:

1. Cervical ligamentous ossification, cervical trauma, cervical cancer, cervical tuberculosis and other inflammatory diseases;
2. accompanied by thoracolumbar spine and other spine parts of the disease affect the clinical symptoms of patients;
3. associated with amyotrophic lateral sclerosis and other motor neuron diseases and other neurological diseases;
4. poor health condition, unable to tolerate surgery;
5. patients (or their guardians) can not give full informed consent for adult dysfunction;
6. patients who have participated in other clinical trials in the past 1 month
7. patients with active hepatitis B (including HBeAg) or serological markers (HBsAg or / and HBeAg or / and HBcAb), hepatitis C, tuberculosis, cytomegalovirus infection, severe fungal infection or HIV infection;
8. patients with active peptic ulcers within 3 months before randomization.
9. patients with malignant neoplasms

The statistical analysist do not know the group assignment.