The Feasibility Study Of Resecting The Anterior Arch Of Atlas Andodontoid Of Axis ,Anterior C1-2 Transarticular Facet Screw Fixation Simultaneously

Objective: To study the feasibility of resecting the anterior arch of atlas andodontoid of axis ,anterior C1-2 transarticular facet screw fixation simultaneously in the aspects of anatomy and biomechanics.Methods: ①: 40 C1,C2 formalin preserved human specimens of native adults were used to measure the significant clinical data. All the data wre: the midposition length and width of C1 superior articular surface ,the midposition length and width of C1 inferior articular facet,the midposition length and width of C2 superior articular surface,the width of midposition to edge of C2 inferior extremity,the midposition length of C2 inferior extremity, the width of anterior arch of atlas,the foot width of odontoid. ②: The rigidity of C1 relative to C2 were measured in 12 specimens after instrument with two ways of fixation. The specimens were divided into two groups: A: Resecting the anterior arch of atlas and odontoid of axis,anterior C1-2 transarticular facet screw fixation simultaneously groups. B: Brooks groups.Result: ①: Anatomical results: The midposition length and width of C1 superior articular surface: 20.57±1.35mm, 10.09±1.31mm; the midposition length and width of C1 inferior articular facet:13.35±1.50mm,12.89±1.24mm;the midposition length andwidth of C2 superior articular surface: 13.56±1.50mm, 13.17 ±1.77mm; the width of midposition to edge of C2 inferior extremity: 10.59±1.43mm,the midposition length of C2 inferior extremity: 10.85±1.18mm,;the width of anterior arch of atlas: 18.69±2.28mm;the foot width of odontoid:10.3±1.45mm. ②: Biomechnic results: The rigidity of AP/PA shearing,rotation of resecting the anterior arch of atlas and odontoid of axis, anterior C1-2 transarticular facet screw fixation was: 473± 66N/mm,478±68N/mm,1.7±0.3Nm/°.The rigidity of AP/PA shearing,rotation of Brooks was: 278±41N/mm,445±86N/mm, 0.3±0.1 Nm/°. The data show all the parameters of applied anatomy more larger than the 4.0mm obviously. There were no significantly difference on AP shearing between resecting the anterior arch of atlas and odontoid of axis,anterior C1-2 transarticular facet screw fixation simultaneously and the Brooks'(p>0.05), but on the rigidity of PA shearing,rotation resecting the anterior arch of atlas and odontoid of axis ,anterior C1-2 transarticular facet screw fixation simultaneously had more higher than the Brooks'(p<0.001).Conclusion: ①: Atlas and axis have enough space for resecting the anterior arch of atlas and odontoid of axis ,anterior C1-2 transarticular facet screw fixation simultaneously. ②: Anterior C1～2 transarticular facet screw fixation provided satisfactory rigidity for clinical use. ③: The modus of resecting the anterior arch of atlas and odontoid of axis,anterior C1-2 transarticular facet screw fixation simultaneously is availabe to simplify the operative procedure.