Image anatomy of percutaneous retrograde screw fixation of acetabular posterior column / 解剖学报

ABSTRACT

Objective To investigate the position, direction and fixation range of retrograde screw of the posterior column of acetabulum based on CT data. Methods Totally 100 cases (50 males, 50 females) of normal adult pelvic CT data were collected from the First Affilated Hospital of Chongqing Medical University. The pelvis was reconstructed by Mimics 17. 0 software and imported into Geomagic Studio 2015 software. The virtual screw was placed in the posterior column from the ischial tuberosity to the iliac fossa, the maximum diameter, the entrance point, the exit point, the direction, safe fixation inclination angles of the screw were measured. The range of the screw fixing, the best fluoroscopic views and the easy-to-penetrate site of the screw in the posterior column were assessed. Results The safe corridor the posterior column of the acetabulum was similar to the "triangular prism" shape. The entrance point was located on the midline of the medial edge and lateral edge of the ischial tuberosity, which were ( 12. 99±1. 99) mm in male and ( 13. 26±2. 58) mm in female from farthest end of the ischial tuberosity. There were no stitistical significant differences between male and female ( P > 0. 05). The exit points was located at the iliac fossa, which were (23. 65 ± 2.42) mm in male and ( 24. 94 ± 2. 39) mm in female to the ipsilateral anterior sacroiliac joint line,and ( 19. 33±2. 60) mm in male and (17.63±2.00) mm in female to the arcus marginalis. The maximum diameters of screw were ( 17. 21±1. 41) mm in male and ( 15. 54±1. 51) mm in female. The angles between screw and coronal plane were ( 15. 00±4. 92)° in male and ( 12. 94±4. 72)° in female; the angles between screw and sagittal plane were ( 10. 52 ± 3. 04)° in male and ( 7. 72 ± 2. 99)° in female. The abore data had statistially significant differences between male and female ( P < 0. 05). Percutaneous retrograde screw could fix the acetabular posterior column fracture that below the 4. 0 cm proximal the horizontal plane of the femoral head center. The easy-to-penetrate sites were the junction of the acetabular posterior wall and the sciatic branch ,the middle part of the acetabulum, and below I. 0 cm of the highest point of greater sciatic notch. The tangential position of three lateral faces of the "triangular prism" were ilium oblique position 10° , the ilium Oblique position 60° and obturator Oblique position 60°. Conclusion The entrance point of the retrograde screw is located on the midline of the ischial tuberosity, which is 1. 3 cm from farthest end of the ischial tuberosity and the direction is forward inclination about 15° , external inclination about 10°. The acetabular posterior column fracture that below 4. 0 cm proximal plane to the femoral head center can be fixed by the retrograde screw.