The patients were operated by the cervical single open-door surgery, which were used with the Centerpiece titanium plate to internal fixation.

The Angle of opening of the cervical unilateral lamina while cervical single open-door surgery

Japanese Orthopedic Association (JOA) score is used to assess the function of spinal cord which is in the form of questionnaires. Postoperative improvement rate = ((postoperative score - preoperative score)/ (17- preoperative score)) X100%. Improvement rate can also correspond to the commonly used efficacy criteria: cure when the improvement rate is 100%, effective when the improvement rate is greater than 60%, effective when 25-60%, and ineffective when less than 25%.

Neck Disability Index (NDI) score is used to assess the disorder of spinal cord which is in the form of questionnaires. Postoperative improvement rate = (total score)/ (numbers of programme X5) X100%. Improvement rate can also correspond to the commonly used efficacy criteria: the improvement rate when 60%-80% means extremely severe dysfunction, when 40%-60% means severe dysfunction, when 20-40% means moderate dysfunction, and when less than 20% means mild dysfunction.

A Visual Analogue Scale (VAS) is used to measure the amount of pain that a patient feels ranges across a continuum from none to an extreme amount of pain. Using a ruler, the score is determined by measuring the distance (mm) on the 10cm line between the "no pain" anchor and the patient's mark, providing a range of scores from 0-100. A higher score indicates greater pain intensity.

This index was measured by MRI, which was the ratio of the diameter of the cervical pulp at the most compressed segment to the mean diameter of the cervical pulp at the upper and lower segments without compression