Anatomical study of the human upper part of the sacrum and ventral rami of the first and second sacral spinal nerves: relevance for sacral fractures management

Abstract

Purpose: This study aims to provide a comprehensive morphological description of the upper part of the sacrum and the ventral rami of the first and second sacral spinal nerves, focusing on their spatial relations with key bony landmarks to improve clinical outcomes in sacral fractures and pelvic trauma management. Furthermore, we intended to evaluate the possible correlation between the studied parameters and the size of the pelvis. Methods: Several measurements related to the bony landmarks of the upper part of the sacrum and the ventral rami of the first and second sacral spinal nerves were taken in 11 carefully dissected embalmed adult human cadavers. Results: Measurements of the ventral rami of the first and second sacral spinal nerves showed median lengths of 3.55 cm and 4.0 cm, respectively, with median widths of 0.9 cm and 0.7 cm, respectively. For the sacrum and sacral foramina, the median length of the anterior border of the sacral ala was 3.6 cm, and the vertical distance from this border to the upper limit of the first pelvic sacral foramen was 1.6 cm. The height and width of the first pelvic sacral foramen were 1.3 cm and 1.2 cm, respectively, while the second pelvic sacral foramen had a height and width of 1.0 cm each. The distance between the first and second sacral foramina was 1.3 cm. The anterior body height of the first and second sacral vertebrae measured in the median plane were 2.9 cm and 2.1 cm, respectively. We found a positive correlation between some of the analysed parameters and the size of the pelvis. Conclusion: The anatomical data of this study are crucial for surgical planning, helping to define safe corridors for instrumentation and reduce the risk of nerve injury during fixation procedures, leading to more effective stabilization and better patient outcomes.