Applied Anatomical Digital Measurements Of Pelvis And Accurate Screw Insertion At Acetabular Area

Purpose: To measure vital anatomical parameters of common fixation routes of pelvis, which locate at the superior border and posterior border of the arcuate line; to investigate the safe placement pathways of screws in acetabular area; to develop the pelvic anatomical internal fixators system based on the measurement results.Materials & Methods: From Dec. 2009 to Nov. 2010, 175 complete pelvic computed tomography scans of unrelated ethnic Han Chinese adults were obtained from Shanghai First People’s Hospital. After the reconstruction of pelvis, the bone thickness, the total length of the fixation route and its radius of curvature were measured. After measuring the anatomical parameters of the pelvic inlet plane, each pelvis was matched with pelvic morphology classification to identify the key bending points of the plates. 100 cases of CT scan data were reconstructed to pelvic models. A space curve was obtained along the fixation route superior border of arcuate line. The acetabular area at the curve was then equally divided to five sections, named section 1 to 5. The range of screws insertion angles from α to βwith the corresponding screw depth d1、d2 were measured; The differences between men and women were compared. The pelvic anatomical internal fixators system was developed according to the measurement results.Results: For the superior border of arcuate line, the bending degrees at pubic turbicle, illiopubic eminence and sacroilliac joint were found greatest, with the radius of curvature 29.18±15.53mm、43.04±14.42mm、43.61±19.10 mm, respectively. For the inferior border of arcuate line, the bending degrees at pubic turbicle, greater sciatic notch and sacroilliac joint were found greatest, with the radius of curvature 52.33±24.10mm、44.01±12.05mm、43.26±21.01 mm, respectively. At the superior border of arcuate line, the α of male and female at section 2 were 22.03±9.49°,28.68±11.81°, respectively. The α of male and female at section 3 were 25.66±12.21°,40.40±12.90°,the β were 44.02±11.57°,51.97± 11.26°, respectively. Significant differences were detected between male and female in α of section 2, α and β of section 3. The mismatch between the internal fixator at superior or inferior border was found within 3 mm.Conclusions: The anatomical parameters at the arcuate line area could provide references to plate bending in surgery; the screw angles at acetabular area could ensure safe screw placement; the pelvic anatomical fixators system was perfectly matched with the pelvis.