Measurement Of Modified Iliac Screws In Chinese Adults By Computerized Tomography

ObjectiveFirst,based on the pelvic CT data of Chinese adults,measure the parameters of modified iliac screw fixation by CT workstation in 3 different directions,and the best direction of them was selected.Second,the parameters was compared between modified iliac screws of the best direction and Second Sacral-Alar-Iliac(S2AI)screw.And then analyze their respective advantages and disadvantages from CT data.Method56 cases of healthy Chinese adult pelvic CT data were collected.Three-dimensional images was reconstructed by CT workstation.In the three-dimensional images,the opening point of the modified iliac screw were located at 1 cm medial and 1 cm caudal from the posterior superior iliac spine(PSIS),and affixed to the medial bone surface of the iliac crest.The opening point of S2 AI screw was located at 1mm to vertical line and the lower 1mm to the horizontal line from the edge of S1 sacrum hole.Rotate the horizontal section to the nail axial lines from 3 different directions of modified iliac screw fixation.The directions adopt anterior inferior iliac spine(AIIS),the upper edge of the acetabulum and the upper edge of the acetabulum plane Head side in the sagittal plane rotation of 5 °.The measurement parameters included maximal length(ML),sagittal angle(SA),transverse angle(TA).Simulate placing a modified iliac screw,which diameter is 7.0mm and the length is 80 mm.The safety scope angle(SSA)was selected.Furthermore,the narrowest width of iliac medullary cavity(IW),the distance from the IW to the starting point(DSP),and the skin distance(SD)were selected.All of the above results were statistically analyzed and compared,respectively for different planes.At the end the parameters was compared between modified iliac screws of the best direction and Second Sacral-Alar-Iliac(S2AI)screw.Results1.The best direction of the modified iliac screw is pointed to 5 ° sagittal upper position from the edge of the acetabulum.In this plane,ML,SSA,IW,DSP,SA,TA,SD are 123.3 ± 8.5 mm,8.6 ± 3.5 °,15.5 ± 2.9 mm,75.8 ± 9.9 mm,28.9 ± 4.0 °,32.4 ± 5.6 °,40.1 ± 4.3 mm.2.Compared with S2 AI screw,the modified iliac screw is better at ML,but inferior at SD.There is no significant difference in SSA,IW and DSP(p> 0.05).3.There were significant differences in the parameters of SA and SD between male and female(p <0.05).There was no significant difference in TA,ML,SSA,IW and DSP between male and female(p> 0.05).Conclusion1.The best direction of modified iliac screw is caudal angle of about 5 ° from the upper edge of the acetabulum.2.Modified iliac screw is a good method for spine pelvic fusion operation,which with better conceal of nail head,no damage of ankle joint and easier achieve.3.There was no significant difference in the TA,ML,SSA,IW and DSP of modified iliac screw between the female and the female.There are more SA in male but less SD.