Minimally Invasive Atlantoaxial Lateral Mass Joint Fusion (MIS-PALF) As a Surgical Treatment of Atlantoaxial Dislocation

Blood loss due to intraoperative bleeding and postoperative drainage.

The time from the completion of surgery to the patient leaving hospital.

The level of patients' occipitocervical pain is described by Numerical Rating Scale, from zero to ten, and ten means the most pain.

The location of patients' occipitocervical pain is indicated by patients on a diagram illustrating the anatomical regions of the head and neck.

Patients are asked about whether they used any painkillers for occipitocervical pain and which painkillers they used.

This metric is defined as the proportion of adverse events that manifest during the study's duration relative to the total number of patients enrolled. Adverse events encompass a range of critical factors, including but not limited to: Neurological deterioration, Incision infection, Vascular injury, Airway obstruction, Poor reduction, Unplanned readmission and re-surgery, Internal fixation failure, Fusion failure, Surgical-related lower cervical spine deformities.

To gauge the effectiveness of the surgical interventions in achieving atlantoaxial reduction, postoperative CT scans of the head and neck will be conducted. Measurements will be taken of the distance between the odontoid process and key reference lines, including Chamberlain's line (CL), Wackenheim line (WL), McRae line (ML), and atlantodental interval (ADI). The reduction rate will be calculated by comparing the postoperative measurements to the preoperative values, expressed as a ratio.

Evaluation of the proportion of patients exhibiting successful bone fusion between the atlas and axis will be conducted through postoperative three-dimensional CT examinations of the cervical spine. The bone graft fusion rate will be determined by calculating the number of patients with evident fusion relative to the total number of patients enrolled.

The quality of life for each patient will be assessed using the Short Form 12-Item(SF-12) Health Survey. SF-12 scores ranges from 0 to 100, and 100 usually means healthier in a certain dimension. The improvement rate in quality of life will be calculated based on the preoperative and postoperative differences in SF-12 scores. This indicator offers insights into the impact of surgical interventions on patients' overall well-being and quality of life, providing a vital perspective on treatment effectiveness.

To assess the extent of neurological function improvement, patients' Japanese Orthopaedic Association(JOA) scores one year after surgery will be compared with their preoperative scores. JOA score ranges form 0 to 17, and 0 means worse neurological function. The JOA improvement rate will be calculated based on the cervical JOA score, employing the Hirabayashi method formula: JOA Improvement Rate = (Postoperative JOA Score - Preoperative JOA Score) / (17 - Preoperative JOA Score) * 100%.