Safety analysis of C 2 laminar screw placement with double hole assisted by computer simulation / 中华骨科杂志

ABSTRACT

Objective:To evaluate the feasibility of C 2 laminar screw fixation with double holes, and to explore a new method to judge the safe position of screws during operation. Methods:There were 22 axial specimens, 11 males and 11 females, aged from 26-69 years (mean 47.2 years). The Dicom format of Cervical spine specimens were obtained by CT scanning. It was transferred into the Mimics software for reconstructing the three-dimensional cervical spine model. The central horizontal plane of the axial lamina was cut off as the measuring plane by using the segmentation function. The cortical bone of the start and end lamina was removed naming hole 1 and 2. The distances of D1 and D2 are measured at the trajectory positions of maximum safe ventral inclination, parallel, or maximum safe dorsal inclination, with each entry point (A, M, P). A paired comparison was performed for each group.Results:Forty-four groups of parallel, introversion and extroversion screw path parameters were obtained from 22 axial specimens, and there was no significant difference between the left D1 and D2 groups in each group A, M, P [group A 3.72±0.95 mm, 3.37±1.24 mm; group M 2.29±0.72 mm, 1.94±0.58 mm; group P 1.17±0.44 mm, 0.86±0.69 mm] ( t=1.051, 1.776, 1.777; P>0.05), while the right D1 and D2 had statistical significance[group A 4.44±1.20 mm, 3.36±1.37 mm; group M 3.01±0.76 mm, 1.97±0.90 mm; group P 2.06±0.73 mm, 1.00±0.87 mm]( t=2.781, 4.141, 4.378; P<0.05). In introversion, there was no significant difference in left D1 and D2 in group M [3.11±0.92 mm, 3.79±1.36 mm] ( t=1.942, P=0.058), and was no significant difference in right D1 and D2 in group M [3.79±1.20 mm, 3.69±1.55 mm] ( t=0.239, P=0.812). In group P, the left D1 and D2 were compared, and the results had statistically differences [2.67±0.77 mm, 4.25±1.39 mm] ( t=4.644, P=0.000). In group P, the right D1 and D2 were compared, and the results were statistically different [2.57±1.14 mm, 3.94±1.53 mm] ( t=3.368, P=0.001). In extroversion, the left D1 and D2 in group A and M were compared, and the results had statistically differences [group A 3.44±1.05 mm, 1.22±0.71 mm; group M 2.26±0.73 mm, 0.90±0.75 mm] ( t=8.215, 6.095; P<0.05); the results of group A and group M were statistically different between groups of D1 and D2 on the right side[group A 4.56±1.51 mm, 1.48±0.97 mm; group M 2.96±1.12 mm, 1.06±0.75 mm] ( t=8.049, 6.611; P<0.05). Conclusion:The double hole screw technique of the C 2 lamina can judge the safe position of the screw in the operation without additional fluoroscopy.