Atlantoaxial subluxation refers to the loss of normal alignment between the articular surfaces of the atlantoaxial and pivotal spine, also known as atlantoaxial subluxation. The atlantoaxial spine is prone to subluxation, which is closely related to its anatomy. The atlantoaxial spine has no vertebral body, and the atlantoaxial transverse ligament is attached to the nodes on the inner surface of the lateral blocks on both sides to prevent the dentate process of the pivot vertebra from moving backward to avoid compression of the spinal cord. There are four joints between the atlanto- and pivotal vertebrae, with the dentate process and the middle of the anterior arch of the atlanto-vertebrae forming the anterior joint, the transverse atlanto-vertebral ligament and the dentate process forming the posterior joint (i.e., the dentate process joint), and the lateral atlanto-vertebrae consisting of two articulating processes on both sides of the lower articular surface of the lateral block and the upper articular surface of the pivotal vertebra. There is no intervertebral disc tissue between the atlantoaxial spine, the joint capsule is large and loose, the joint surface is flat, and the range of motion is large, i.e., the local anatomical structure is not strong enough and the stability is poor. When the neck suffers acute trauma, atlantoaxial dentate fracture and atlantoaxial transverse ligament rupture can occur, along with atlantoaxial dislocation. It is generally accepted that anterior and posterior movement of the atlantoaxial spine of more than 10 mm is likely to compress the spinal cord. A fracture of the body of the dentate process often results in bone discontinuity in 1/3 of the fractures, which can cause atlantoaxial instability and delayed dislocation, resulting in spinal cord compression. Any infection of the neck and nasopharynx, including septic or atopic infection, inflammation can involve the atlantoaxial joint or transverse ligament, which can cause congestion and swelling of the local bones, joint capsule ligament and transverse ligament, ligament relaxation, and when the cervical spine is in a flexed position, the anterior arch of the atlantoaxial spine is easily displaced forward and the joint is dislocated when there are congenital deformities of the atlantoaxial spine such as dentate dysplasia, dentate agenesis, dentate ossification, occipito-atlantoid congenital fusion deformity, or rheumatoid arthritis, pontine osteoma, atlantoaxial tuberculosis, etc., spontaneous atlantoaxial dislocation can occur without a history of obvious trauma. What are the manifestations of atlantoaxial subluxation? Atlantoaxial subluxation is more common in children, mostly due to trauma or neck infection, and the atlantoaxial spine can have forward, rotational and lateral subluxation lesions on the cardinal spine. There are babbling sounds, numbness in the occipital pain and a sense of head falling forward. When the atlantoaxial dislocation is accompanied by rotational displacement, the head may be tilted to one side. Children with atlantoaxial subluxation due to head and neck trauma mostly show oblique neck signs; 2. vertigo or visual impairment: vertigo or visual impairment can occur when the atlantoaxial spine is dislocated forward and the vertebral artery located in the transverse foramen of the atlantoaxial spine is strained and causes insufficient blood supply; 3. symptoms caused by damage to the cervical or medulla oblongata: cervical spinal cord compression lesions can cause limb numbness, limb weakness, cervical muscle atrophy, finger fine motor impairment, unstable walking and cottony feeling. Ischemic lesions of the medulla oblongata can manifest as motor paralysis of the extremities, dysarthria and dysphagia. X-ray examination is the most reliable diagnostic method for atlantoaxial subluxation. In addition to cervical lateral X-ray, atlantoaxial open position and cervical functional position films should be taken to observe the displacement. In atlantoaxial subluxation, the gap between the dentate process and the lateral blocks on both sides of the atlantoaxial spine can be seen to be significantly different in the cervical open position X-ray, and the joint gap between the joint processes on both sides is asymmetrical, narrowing, disappearing or overlapping on the affected side, and the form and size of the joint processes are also asymmetrical; if the atlantoid spacing is widened in the cervical lateral X-ray, or if the atlantoid spacing is normal in the neutral position but the atlantoid spacing is widened in the cervical anterior flexion X-ray, it indicates that the transverse atlantoaxial ligament rupture or laxity of the atlantoaxial ligament. The atlanto-dental spacing is the shortest distance between the posterior lower edge of the atlanto-axial arch and the anterior edge of the dentate process, and is normally less than 3 mm in adults and less than 4.5 mm in children. How is atlantoaxial subluxation treated? Once atlantoaxial subluxation is diagnosed, time should be taken to reset it as soon as possible. If the subluxation occurs suddenly, it is easy to achieve a successful reset. There are two types of resetting: manual resetting: for patients with mild condition, light manual resetting is feasible, note that the resetting technique should not be too violent or use improper force, otherwise it is easy to cause spinal cord damage, and after resetting, the neck activity should be restricted with a plaster collar for 6 weeks; cervical continuous traction resetting: that is, for atlantoaxial dislocation that is difficult to be treated by manual treatment or not suitable for manual treatment, cervical traction with occipito-mandibular band should be performed in children in supine position with head and neck in hyperextension position. In adults, cranial traction should be performed to gradually increase the weight, and when the continuous traction is more satisfactory, the traction should be continued for 6-8 weeks, and then the plaster collar or cervical brace should be fixed for 10-12 weeks, so that the joint capsule tissue and ligaments can reach the repair requirements and the relative stability of the atlantoaxial joint can be maintained. For patients with inflammatory and spontaneous atlantoaxial dislocation: firstly, the cause of inflammation should be removed and anti-infection treatment with antibacterial agents should be given priority. In some cases where the atlas cannot be repositioned or the repositioning is incomplete, surgical treatment can be considered by performing atlantoaxial wire internal fixation and bone graft fusion; for those with combined spinal cord damage, the posterior arch of the atlas can be removed to obtain spinal cord decompression, and occipitocervical fusion can be performed, but the range of cervical flexion and extension will be lost by 30% after surgery. For patients with atlantoaxial fracture with atlantoaxial subluxation: it is advisable to reset the cervical traction first, and after 8-12 weeks of continuous traction, change to head-neck-thoracic cast to take the cervical hyperextension position for 4-6 weeks; if the patient still shows atlantoaxial subluxation on the lateral X-ray of cervical hyperextension and hyperextension, it is feasible to perform atlantoaxial wire internal fixation with bone graft fusion to prevent late onset myelopathy. to prevent the occurrence of late onset myelopathy. In patients with old atlantoaxial fractures, bone discontinuity, and anterior atlantoaxial dislocation combined with spinal cord damage, posterior atlantoaxial arch resection and decompression and occipitocervical fusion are recommended. For congenital dentate dysplasia, dentate agenesis, and atlantoaxial dislocation caused by dentate tooth ossification: atlantoaxial wire internal fixation with bone graft fusion should be used; if more obvious spinal cord damage has occurred, posterior atlantoaxial arch decompression and occipitocervical fusion should be removed, and the patient should be bedridden for 3 months after surgery.