ABSTRACT
BACKGROUND: Chinese anatomical parameters of antedor atlantoaxial transarticular screw fixation have been rarely reported although the technique is a novel method out of China for patients with C1-C2 instability. OBJECTIVE: To provide Chinese anatomical data for anterior C1-C2 transarticular screw fixation. DESIGN, TIME AND SETTING: A measurement experiment was performed at the Department of Anatomy, Southern Medical University and Department of Orthopedics, Wuhan General Hospital, Guangzhou Command of Chinese PLA between September 2006 and April 2008. MATERIALS: A total of 50 sets of dried Chinese adult human C1 and C2 specimens, without regard to gender and age, but no abnormality and breakage, were measured with an electronic digital caliper (precision 0.01 mm) and a goniometer(precision 0.5°) made in China. METHODS: One proper screw was drilled through the atlantoaxial joint respectively in the direction to middle part of laterosuperior angle in the posterior of C1 lateral mass, and the screw point should not break through the superior facet articularsurface of the C1. In the procedure, the screw drilling point was at the junction of the lateral border of C2 body to 4 mm above the inferior border of C2 anterior arch. border of transverse foramen of C2 body and the median line of C2 body, and the distance between the inserting point and the medial border of transverse foramen of C2 body. RESULTS: The data from all specimens were involved in the result analysis. In the sagittal plane, the minimum lateral angulation of the screw tract was (10.80±2.10)°(left) and (10.76±2.40)°(right) respectively, and the maximum lateral angulation was (25.13±3.12)°(left) and (25.12±2.86)°(right), respectively. In the coronal plane, the minimum posterior angulation was (8.85±2.12)° (left) and (9.28±2.65)° (right) respectively, and the maximum posterior angulation was (26.96±3.09)°(left) and (27.49±2.51)°(right), respectively. The left screw tract length was from (17.48±2.10) mm to (25.41±2.59) ram, and the right was from (17.49±2.23) mm to (25.58±2.42) mm. The left distance between the inserting point and the median line of C2 body was (9.84±0.69) mm, and the right was (9.81±0.66) mm. The left distance between the median line of C2 body and medial border of transverse foramen of C2 body was (14.12±1.28) mm, and the right was (14.60±1.36) mm. The left distance between the inserting point and medial border of transverse foramen of C2 body was (6.28±1.38) mm, and the right was (6.79±1.39) mm. CONCLUSION: It is optimal for the anterior C1-C2 transarticular screw fixation to place the antedor screw with a length of 17 to 25 mm in lateral angulation ranging from 10° to 25° and the posterior angulation ranging from 9° to 27°. During the procedure, the dissecting distance from the middle of C2 body to lateral should not exceed 14 mm.