Optimal entry points of screw in internal fixation of acetabular posterior column fracture with plate

Background: Recently, open reduction and internal fixation has become a common therapy for pelvic and acetabular fractures. However, screw penetration sometimes damages important vessels or nerves in the pelvic cavity during the internal fixation. Objective: To investigate the optimal entry points, direction and length of screw in acetabular posterior column plate technique, and to prevent the serious complications caused by screw penetrating the joint surface. Methods: Twenty male cadaveric adult semipelvic specimens were taken and prepared into serial cross-sections of the acetabular posterior column. The safe angle of screw entry and the length on all entry points of each cross-section were measured. All data were input into software SPSS 10.0 for statistical process. Results and Conclusion: On margin of acetabulum, lateral-middle 1/4 point, midpoint, medial-middle 1/4 point and medial margin of posterior column of each cross-section, safe entry angle of inclination was 39°, 57°, 74°, 90° and 106°respectively, the length of the screw was 39, 57, 74, 90 and 106 mm respectively. On lateral 1/4 region, lateral-middle 1/4 region, medial-middle 1/4 region and medial 1/4 region, screw posterior column angle was 40°-60°, 60°-75°, 75°-90°, 90°-parallel to the quadrilateral plate, and the length of the screw was 30 mm.