| Objective: To investigate the osseous channel for iliosacral screw insertion throughthree-dimensional computed tomography (3-D CT) reconstruction method to determine theparameters of sacroiliac joint screw path during the iliosacral screw fixation process.The study is to develop an appropriate method for screw insertion by investigating therelationship between bone landmark of the pelvic and the osseous channel for screwinsertion. In addition, the study is to improve the safety of operation by the research on therelative safety area.Materials and Methods:Forty normal pelvic CT images were randomly selected among the images stored in theCT room of the First People’s Hospital of Chenzhou. All the images were stored in a dicomformat.3-D CT reconstruction was performed using ADW4.2work station of GE MedicalSystems. The parameters of the sacroiliac joint screw path were measured. The scale of thesafe operating region together with its parameters was evaluated. SPSS19.0software wasused for the statistical analysis.Results:The height and width of the narrowest site in the pedicle of vertebral arch of the firstsacral vertebrae (S1) were20.45±1.48mm and20.60±2.09mm, respectively. The distancebetween the optimal entry point (OEP) of the screw and the center of the narrowest site ofthe pedicle was45.46±4.42mm. The distance between the OEP and the frontal cortexlocated at the opposite side of vertebral body was87.90±5.63mm. The distance betweenOEP and posterior superior iliac spine (PSIS), posterior inferior iliac spine (PIIS) as well asgreater sciatic notch (GSN) were52.01±7.12mm,52.56±6.76mm and46.40±5.06mm,respectively. The distance between the PSIS and PIIS was52.87±7.00mm. The angleformed between the screw and the horizontal plane was20.85±2.43°. The angle formed between the screw and the coronal plane was30.35±2.46°. The cross sectional area andthe coronal area of the safe operating region in S1were1439.99±146.35mm2and1434.56±125.34mm2, respectively. The angle modulation of the screw in the crosssectional plane and the coronal plane were4.88±1.06°and7.54±1.13°, respectively. Theheight and width of the narrowest site in the pedicle of vertebral arch of the second sacrum(S2) were17.54±3.57mm and18.25±3.06mm, respectively. The distance between OEP ofthe screw and the center of the narrowest site of the pedicle was45.45±5.43mm. Thedistance between OEP and the frontal cortex located at the opposite side of the vertebralbody was70.05±7.03mm. The distances between OEP and PIIS as well as GSN were22.10±4.55mm and17.94±3.54mm, respectively. The angle formed between the screw andthe horizontal plane was14.41±1.74°. The angle formed between the screw and the coronalplane was13.36±2.74°.Conclusions:The entry point of S1screw was located at the apex of an equilateral triangle. The lengthof the bottom margin equals the direct distance between PSIS and PIIS. The entry point ofS2screw was located on the direct line of PIIS and OEP of S1screw. With regards to theOEP of S1screw, the angle formed between the screw and the horizontal plane was20.85±2.43°. The angle formed between the screw and the coronal plane was30.35±2.46°For the OEP of S2screw, the angle formed between the screw and the horizontal plane was14.41±1.74°. The angle formed between the screw and the coronal plane was13.36±2.74°.For those with effective internal fixation obtained after using S1screw, a screw with adiameter of7.3mm and a length of65mm was more efficient for the fixation. For thosewith effective internal fixation obtained after using S2screw, a screw with a diameter of6mm and a length of60mm was more efficient for the fixation. The screw parametersvaried according to the individual anatomy. Individual specific treatment plan could beestablished based on the preoperative CT images, especially those with unilateral posteriorpelvic ring. The angle modulation of the S1screw in the horizontal plane and the coronalplane were4.88±1.06°and7.54±1.13°, respectively. The angle modulation decreased with the increase of the length and the diameter of the screw. |
PDF Full Text Request