Abstract
Objectives This study aims to investigate screw insertion sites on the pubic body and the safe screw insertion parameters of a plate-screw fixation system based on the premise of avoiding damage to the inguinal canal and disruption of the rectus abdominis at the pubic symphysis and pubic crest. Research Methods Excluding cases with poor image quality, tumors, malformations, and fractures, the data of 80 healthy adults (40 males and 40 females aged from 21 to 83 years old, with an average age of 51.65 years) undergoing a computed tomography (CT) scan of the pelvis between January and June of 2017 were collected from Shandong Provincial Hospital. The CT scans were imported to Mimics® software to reconstruct three-dimensional pelvic models. A 3.5 mm pelvic reconstruction plate was placed starting at the outer edge of the pubic tubercle and along the pelvic brim. The two innermost screw insertion sites were marked. The safe range for the screw insertion sites was then determined. The screw insertion plane was selected to measure the safe screw insertion parameters. The length of the screw, the direction of insertion, and intersex differences were then explored via statistical analyses. Results The medial inclination angles (MIAs) of the screw insertion plane for males and females were 30.42±7.95° and 32.88±10.65°, respectively, with no statistically significant differences. For the medial screw, the maximum anterior inclination angle (MAIA), the maximum screw length, and the maximum posterior inclination angle (MPIA) were 46.51±4.01°, 12.40±9.53 mm, and 11.78±10.22° on average, respectively, with no significant differences by gender (P>0.05). For the lateral screw, the MAIA was 10.35±9.46° and showed no gender differences (P>0.05), but the male group had a greater MPIA (male 11.80±11.00° vs. female 6.23±7.91°, P<0.05) and maximum screw length (male 55.71±6.36 mm vs. female 48.68±8.65, P<0.001). For the tangential screw, the maximum screw length, MIA, and anterior/posterior inclination angle (APIA) were 52.19±8.33 mm, 31.65±9.42°, and 7.53±10.18°, respectively, with no significant differences in the angles by gender (both P>0.05), although the screw length in the male group was significantly longer than that in the female group. Conclusions Insertion of two screws into the pubic body through a plate from the lateral side of the pubic tubercle is safe and can maintain the origin of the rectus abdominis and the integrity of the inguinal canal compared to traditional plate-screw fixation. Considering that the pubic body is thinner on the lateral side, we suggest a more medial inclination angle for the lateral screw.
Highlights
The pelvis is a complicated structure comprising the posterior sacrum and bilateral hip bones and exhibits considerable variations in geometrical and mechanical features
We investigated screw insertion sites and safe insertion parameters based on 3D reconstruction of the normal pelvis using computed tomography (CT) data
This study aims to investigate screw insertion sites on the pubic body and safe screw insertion parameters for a plate-screw fixation system based on the premise of avoiding damage to the inguinal canal and disruption of the origin of the rectus abdominis muscle to improve the safety of screw placement during surgery
Summary
The pelvis is a complicated structure comprising the posterior sacrum and bilateral hip bones and exhibits considerable variations in geometrical and mechanical features. Tile et al [1] found that the posterior ring provides approximately 60% of pelvic stability, whereas the anterior ring provides the other 40%. A finite element analysis of lateral pelvic trauma [2] found that the anterior region of the pelvis is most sensitive to the force of trauma, and the pubic branch was usually fractured first. The acetabular anterior column is thinner than the posterior column, the former provides 2.75 times more pelvic stability than the latter [3]. The anterior ring of the pelvis can be fractured and restoring its integrity is critical for improving pelvic stability
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