A review of the diagnosis and treatment of atlantoaxial dislocations

Abstract

Study Design Literature review. Objective Atlantoaxial dislocation (AAD) is a rare and potentially fatal disturbance to the normal occipital-cervical anatomy that affects some populations disproportionately, which may cause permanent neurologic deficits or sagittal deformity if not treated in a timely and appropriate manner. Currently, there is a lack of consensus among surgeons on the best approach to diagnose, characterize, and treat this condition. The objective of this review is to provide a comprehensive review of the literature to identify timely and effective diagnostic techniques and treatment modalities of AAD. Methods This review examined all articles published concerning "atlantoaxial dislocation" or "atlantoaxial subluxation" on the PubMed database. We included 112 articles published between 1966 and 2014. Results Results of these studies are summarized primarily as defining AAD, the normal anatomy, etiology of dislocation, clinical presentation, diagnostic techniques, classification, and recommendations for timely treatment modalities. Conclusions The Wang Classification System provides a practical means to diagnose and treat AAD. However, future research is required to identify the most salient intervention component or combination of components that lead to the best outcomes.

Keywords: atlantoaxial dislocation; atlantoaxial subluxation; classification; comprehensive review; diagnosis; treatment.

Fig. 1

Schematic representation of atlantoaxial dislocation. Lateral view of the normal cervical spine in relation to the occiput (left) compared with an abnormal relationship between the cervical spine and occiput representing an atlantoaxial dislocation (right). An increase in the distance between the anterior surface of the dens and the posterior surface of the C1 tubercle (A) as measured by the gray arrowed line is shown. The dotted line represents an imaginary line connecting the spinolaminar white lines (the junction between the lamina and the spinous process) and shows that the body of C1 (B) is displaced anteriorly relative to the cervical spine. The atlantodental interval (ADI) is measured between the posterior aspect of the anterior atlas ring and the anterior aspect of the odontoid process. The ADI is often constant in distance during movement of the head and generally does not exceed 3 mm for adults and 5 mm for children. Atlantoaxial dislocation is defined as ADI greater than 3 mm in adults older than 18 years of age and greater than 5 mm in children.

Fig. 2

Neutral (left), extension (center), and flexion (right) lateral X-rays showing the atlantodental interval (ADI) anterior to the odontoid process and the space available for spinal cord posteriorly. The ADI is above the average for adults of 3 mm and is slightly reduced in extension, but severely increased in flexion. This patient's space available for spinal cord (SAC) reducing to below 14 mm indicates risk of paralysis.

Fig. 3

A schematic representation of the traction technique involving three stages to reposition the joint. In the initial distraction phase (A), the patient is placed in slight flexion to keep the ring of C1 opposed to the posterior odontoid and to avoid hitting the spinal cord as traction weight is gradually added. After full distraction, the realignment phase (B) will occur when C1 slips back over the odontoid. Excessive flexion during distraction could cause the ring to slip too far forward. The release phase (C) consists of switching to an extension posture and slowly releasing traction over several hours with gradual weight reduction. Note the gradual realignment of the occiput to the cervical spine, as denoted by the decreasing atlantodental interval (black arrows).