Introduction: Percutaneous retrograde screw fixation of the anterior column has been recommended for the treatment of minimally displaced acetabular fractures. However, proper placement of the screw in anterior column is challenging because of its unique anatomy. There are few anatomic studies on this technique, and the differences between male and female have never been reported.
Methods: We created virtual three-dimensional reconstruction models of the pelvis from CT scan data obtained from 82 adult patients without any bony problems. Virtual cylindrical implants were placed intraosseously both in left and right anterior column. The maximum diameter, length and optimal direction of the virtual cylindrical implant were determined for the screw. The perpendicular distance from the insertion point (P) of virtual cylindrical implant to the pubic symphysis (A) and the rim of superior ramus of pubis (B) were measured respectively. In the same model, cross-sections of the anterior column were created and the diameters of them were measured.
Results: 164 (80 males and 84 females) hemipelvis models were obtained. The mean maximum diameter and length of virtual cylindrical implant were 8.16+/-1.21 mm (range: 5.60-10.80 mm) and 109.39+/-8.95 mm respectively. The angles of the virtual cylindrical implant to transverse, coronal and sagittal planes were 39.66+/-3.92 degrees , 20.81+/-4.58 degrees and 42.66+/-3.23 degrees respectively. The distance of PA and PB were 18.42+/-4.82 mm and 17.76+/-2.63 mm. Both the differences of the diameter and length of the virtual cylindrical implant, and the distance of PA between the male and female were of statistical significance (p<0.00001). The mean minimum cross-sectional diameter of anterior column was larger than the mean diameter of the virtual cylindrical implant.
Conclusions: The anterior column of a male will accommodate a 6.5mm lag screw very well, but it does not fit all the females. The same direction of screw can be used in both male and female, but the insertion points of the screw are different. In addition, the determination of the size of the screw used for the anterior column cannot be based solely on the measurement of cross-sectional diameter and the virtual three-dimensional reconstruction model might be useful in preoperative planning.