Iliopubic rami morphology and its vascular relationships in percutaneous retrograde fixation

Abstract

Purpose: Pelvic ring fractures involving the iliopubic rami can cause functional impairment. Percutaneous retrograde fixation is a less invasive procedure when compared to traditional open approaches, however precise anatomical knowledge is crucial for safe screw placement. This study aims to describe the morphology of the iliopubic rami, define a safety corridor for percutaneous screw fixation, specially focusing on the relationships between the iliopubic rami and neurovascular structures.

Methods: A retrospective cross-sectional study was conducted on 29 patients using high-resolution computed tomography scans. Measurements included rami shape, narrowest diameter, and distances between the iliopubic rami and neurovascular structures. Statistical comparisons were performed using the Wilcoxon, Mann-Whitney, and Kruskal-Wallis tests.

Results: Triangular and trapezoidal rami shapes were most common being the median narrowest diameter larger in males (8.67 mm) than females (6.83 mm) (p = 0.011). The obturator neurovascular bundle was approximately 3 mm from the iliopubic rami, while the external iliac vein and artery were about 5 mm and 11 mm away, respectively. Women also had a greater external iliac vein proximity to the iliopubic rami on the left, compared to men (p = 0.032).

Conclusion: Therefore, preoperative imaging is essential to reduce neurovascular risks and given anatomical variations, screw selection should be sex-specific, with 6.5 mm screws for males and 4.5 mm for females. The polygonal rami shapes allow the use of straight plates. The obturator neurovascular bundle is highly vulnerable during screw placement as so it is the external iliac vein compared to the homonym artery, especially in women.

Keywords: Iliopubic rami anatomy; Neurovascular structures; Percutaneous retrograde fixation; Safety iliopubic corridor.

Fig. 1

CTs iliopubic rami categories assessment. a Triangular; b Circular; c Quadrangular; d Trapezoid. a- anterior; s- superior.

Fig. 2

CTs morphometric and neurovascular obturator bundle parameters assessment a diameter of IP rami; b IP rami axis, neurovascular obturator bundle (white dashed circle) distance to IP rami, distances from the PS to the, neurovascular obturator bundle (1), medial and lateral limits of acetabulum (2) (3) and cephalo-caudal angle (4); c minimal coronal acetabulum thickness; d predicted screw trajectory in acetabulum; e minimal sagittal acetabulum thickness. s- Superior; s- Anterior; r- Right; The yellow line represents the localizer

Fig. 3

CTs external iliac vessels parameters assessment. a identification of external iliac vessels; b position of external iliac vessels in relation to IP rami axis; c external iliac vein relation to IP rami axis; d external iliac vein horizontal distance to IP rami; e external iliac vein sagittal (blue dashed circle) distance to IP rami. Red and blue asterisks represent the external iliac artery and vein, respectively. s- Superior; a- Anterior; r- Right; The yellow line represents the localizer

Fig. 4

Angles comparison among non-reduced fractures (n = 7) reduced fractures (n = 5) and without fracture (n = 13) cases on the left side

Fig. 5

Iliopubic rami diameter comparison among non-reduced fractures (n = 7) reduced fractures (n = 5) and without fracture (n = 13) cases on the left side