A Computed tomography (CT) based morphometric study of superior pubic ramus anatomy among Arabs to determine safe intramedullary pubic rami screw insertion

Abstract

Purpose To measure the morphometric variables of the superior pubic ramus in a sub-set of an Arab population to establish a safe pubic screw fixation technique. Methods Cross sectional retrospective analysis of computed tomography (CT) pelvis images for 231 participants. The morphometric analysis included; pubic ramus axis length, insertion angles orientation, distance from the exit point to the pubic symphysis, distance from the entry point to acetabular joint surface and assessment of the narrowest pubic ramus diameter at three anatomical zones: para-symphyseal, mid-pubic and supra-acetabular areas. Pubic rami diameter correlation with age and sex was also analyzed. Results A total of 231 participants were included (55% male, 45% female). The mean screw length was between (104–127 mm) and it is significantly higher in males than females. The narrowest canal diameter was found at the para symphyseal area in both sexes were; 7.35mm in males and 4.75 mm in females. In females, all canal diameters at the three measured regions were significantly smaller than male’s diameters. The mediolateral insertion angle was significantly higher in females than males (49.4° vs. 41.8°, respectively), whereas the cephalic-caudal angle was significantly higher in males than females (49.9° vs. 42.1° respectively). The mean distance from the lateral ilium entry point to joint articular surface was higher in males (23.5 mm) than females (19.9 mm).The symphysis pubis to tubercle exit point was significantly higher in females than males (24.2 mm vs 16.6 mm respectively). Pearson’s correlation analysis revealed a statistically significant positive correlation between age and the pubic ramus diameter at the three measured regions in all age groups. Conclusion The results from this study suggest that percutaneous pubic rami screw fixation using the standard 6.5 or 7.3mm cannulated screw system may potentially be unsafe in female Arab patients. Thus, a closer evaluation in this subset of patients may require the alternative solid non-cannulated screws (3.5- 4.5mm) or plate fixation options. Further, female patients may have a higher risk of acetabular joint penetration, while males have a potentially higher risk of pudendal nerve injury