Morphometric Measurement And Design Of Positioning Navigation Template Of Sacral Alar-iliac Screw Fixation In An Adult Population Using Forward Engineering

Objective We evaluated S1AI-S4 AI screw channels with three-dimensional digital technology simulation analysis and explored a digital anatomic method for accurate positioning of the ideal S1AI-S4 AI screw channels to provide anatomical basis and a new method for clinical applications.Methods Forty(20 men and 20 women)normal adult’s pelvic CT scan datasets were selected to reconstruct the three-dimensional pelvic model,simulate the S1AI-S4 AI screw channels and measure the parameters of the ideal S1AI-S4 AI screw trajectories.Meanwhile we established a positioning navigation template that was consistent with the model shape.Results(1)Through the digital technology positioning,quantitative analysis and design,we got the ideal S1AI-S4 AI screw channels,accurate data and method of designing personalized navigation templates,and the reconstructed navigation templates have good matching.(2)There was no significant difference about the transverse angles,sagittal angles,radiuses of the maximal inscribed circle and length of screw channel between genders in S1AI-S2 AI screws(P > 0.05).(3)There was no significant difference about the transverse angles,sagittal angles and length of screw channel between genders in S3 AI screws(P > 0.05).The radiuses of the maximal inscribed circle on the left and right respectively were 5.93 ± 1.02 mm and 5.92 ± 1.04 mm in males,4.64 ± 0.98 mm and 4.59 ± 0.95 mm in females,and showed significant difference between genders(P < 0.05).(4)Referred to the radius = 2.50 mm as standard,there were 25 cases(62.5 %)with the radius ≤ 2.50 mm in 40 adults of S4 AI screw channels,15 cases(37.5 %;9 males and 6 females)with the radius > 2.50 mm.In cases with the radius > 2.50 mm,the transverse angles on the left and right respectively were 105.02 ± 13.23 ° and 106.38 ± 11.21 ° in males,95.16 ± 13.35 ° and 93.82 ± 13.03 ° in females.The sagittal angles on the left and right respectively were 104.90 ± 12.30 ° and 105.48 ± 9.94 ° in males,95.97 ± 12.93 ° and 93.03 ± 11.92 ° in females.The length of screw channel on the left and right respectively were 162.94 ± 5.57 mm and 163.11 ± 6.17 mm in males,153.62 ± 11.50 mm and 152.24 ± 13.22 mm in females.The radiuses of the maximal inscribed circle on the left and right respectively were 3.04 ± 0.29 mm and 3.05 ± 0.30 mm in males,3.66 ± 0.64 mm and 3.78 ± 0.83 mm in females.The transverse angles,the sagittal angles,the length of screw channel and the radiuses of the maximal inscribed circle showed significant difference between genders(P < 0.05).Conclusion(1)The application of modern imaging and computer-aided design techniques could be individually,quantitatively designed for the S1AI-S4 AI screw channels and positioning navigation templates,providing a new method of sacral alar-iliac screw fixation.(2)There were the S1AI-S4 AI screw channels in adults.Only one maximum ideal screw could be placed on one side at a time.(3)Referred to the radius = 2.50 mm as standard,it was feasible to place S1AI-S3 AI screws with the radius > 2.50 mm in the entire adult population and S4 AI screws with the radius > 2.50 mm in some of the adult population.