Digital virtual technique in determining the optimal sacroiliac screw channel

English Keywords:Sacroiliac joint  Sacroiliac screws  Computed tomography  Digital virtual technique  Sacroiliac screws channel

English Abstract:

  【Abstract】 Objectives: To explore digital virtual technique(DVT) to determine the optimal sacroiliac screw channel(OSSC), and to provide a method for instrumentation under navigation. Methods: The pelvic CT scan data of 8 healthy adults were processed into Mimics 10.01 for 3D reconstruction. DVT was used to establish the model of sacral cavity die, which was used to determine the OSSC, and the associated parameters were measured by using computer aided design(CAD) and Space Analytical Geometry′s(SAG) method. Results: The OSSC of 16 S1 pedicles in 8 cases was determined by this way. The radius of the OSSC was greater than 7.3mm in both side of all the cases, which the radius of the OSSC was 8.75±0.72mm for male, and 8.38±0.67mm for female. The depth was 78.44±3.43mm for male, and 74.07±6.04mm for female. The introversion angle in sagittal plane was 72.62°±5.01° for male, and 79.65°±7.59° for female. The angle in cross-sectional plane was 13.28°±6.33° for male, and 9.60°±4.17° for female. The angle in coronal plane was 9.99°±7.67° for male, and 2.01°±1.58° for female. The angle in upper face of S1 vertebral was 14.91°±6.48° for male, and 7.62°±5.88° for female. On fluoro-navigation images, the starting point of S1 OSSC was 3∶5 in up-down direction and 2∶5 in left-right direction on out-let view, while 5∶2 in up-down direction on in-let view. The end-ponit of S1 OSSC was 2∶5 at the max length of pelvis in up-down direction and midpoint in left-right direction on out-let view, while 3∶1 in up-down direction on in-let view. The end-point of OSSC was also 2∶3 at the axis wire of S1 vertebra and 3∶5 at the max length of S1 vertebra in anterior-posterior direction. The angles in sagittal plane, coronal plane, and upper surface showed sex-related statistical differences(P<0.05), while the others showed no statistical difference(P>0.05). Conclusions: DVT is guided to measure and determine the OSSC. The bilateral OSSC of S1 is symmetrical, and can hold 2 sacroiliac screws.