Anatomic Observation of the atlanto-axial Joint in Functional Positions by CT three-dimensional Imaging

BACKGROUND: Clinical diagnosis criteria for rotary subluxation of atlanto-axial joint have not been identified. Mans clinical diagnoses are suspicious. Therefore, investigating a new diagnostic method and diagnostic evidence is beneficial to enhancing diagnosis accuracy, and is a study hotspot in the current field. OBJECTIVE: This study aimed to observe the retationship between anatomy of normal human atlanto-axial joint and functional positions, and to provide anatomical basis for the diagnosis of atlanto-axial rotary subluxation. DESIGN: Single sample self-control study. SETTING: Department of Imageology, Zhongshan Hospital Affiliated to Xiamen University. PARTICIPANTS: This study was carried out in the CT Room, Department of Imageology, Zhongshan Hospital Affiliated to Xiamen University between June 2003 and November 2004. Fifty-three volunteers. 27 males and 26 females, with an average age of 31.2 years (range 4.5-75 years), without cervical trauma or history of cervical diseases. were randomly recruited in to this study. Written informed consents were obtained from each subject or their guardians. METHODS: CT helical scanning and three-dimensional reconstruction imaging of atlanto-axial ml in the neutral position were performed in all the volunteers and were supplemented in the right and left rotary position in 21 subjects on a helical CT scanner (somatom plus 4, Siemens, Germany), SUN magic view 1000 workstation and three-dimensiorial reconstruction software. MAIN OUTCOME MEASURES: ①Lateral atlanto-axial articular facet contraposition. ②Lateral atlanto dental space. ③Atlanto dental interval. ④The largest extent of articular facets dislocation in the right and left rotary positions. ⑤Head's rotary maximal angle in the right and telt rotary positions. RESULTS: ① Three-dimensional images with atlanto-axial joint in the functional position of 53 patients showed that the irticular surfaces of lateral atlanto axial joint had basic contraposition, the width of atlanto-dentat inlersal ranged from 1.0 to 3.3 mm, and the lateral atlanto-dental distance devirated in 24 patients (45.28%). ② Three-dimensional images with atlanto-axial joint in the rotary position of 21 patients showed that the width of atlanto detital interval had no change, the articular facets of lateral atlanto-axial joint had rotary displacement with the width ranging from 5.76 to 1.18 mm. and anastomotic area of articutar facet was decreased by 1/2 to 2/3. The condyles had deflected to the rotary direction in the patients with symmetrical lateral atlanto dental space, and for 15 patients with asymmetrical lateral atanto dental space, the condyle deflected slightly or had no changes. CONCLUSION: CT-three dimensional imaging can clearly show the anatomical structure of adanio-axial joint in functional position and the changing rule of atlanto-axial joint movement, providing theoretical evidence for the cliniral diagnosis and the treatment of atlamo-axial subluxation.