Comparison of accuracy of three kinds of second sacral alar iliac screw placement techniques

Abstract:

Objective To compare the accuracy of the conventional freehand technique，three-dimensional printed template-guided technique（TGT），and ball tip technique for second sacral alar iliac（S2AI） screw placement.Methods One hundred and forty-five patients who underwent S2AI screw placement were retrospectively reviewed. According to the screw placement techniques，they were divided into freehand technique group（36 cases），TGT group（48 cases），and ball tip technique group（61 cases）. All the patients underwent computed tomography before operation to identify the parameters of the optimal trajectory of S2AI screws and also after operation to assess the accuracy of the screw trajectory. The accuracy of screw insertion with the three techniques was compared.Results There were no significant differences in the optimal trajectory parameters of S2AI screws between the three groups（P>0.05）. A total of 290 S2AI screws were placed，with 72 in the conventional freehand technique group，96 in the TGT group，and 122 in the ball tip technique group. The inaccuracy rate of screw placement was 18.1%（13/72） for the freehand group，3.1%（3/96） for the TGT group，and 4.1%（5/122） for the ball tip group. The accuracy of the TGT group was significantly higher than that of the freehand group（P<0.05）. The accuracy of the ball tip group was also significantly higher than that of the freehand group（P<0.05）. The accuracy of screw placement was higher in the TGT group than in the ball tip group，but the difference was not statistically significant（P>0.05）.Conclusion The TGT technique and ball tip technique are reliable approaches to S2AI screw placement，both with significantly higher accuracy compared with the freehand technique，and in addition，the ball tip technique is easier to perform compared with the other two techniques.