Establishing the safe use of the Bridging Infix method for anterior pelvic fixation in a South African sample

Abstract

The Bridging Infix was proposed as a novel minimally invasive technique for anterior pelvic fixation. The novel method was proposed with the objective of reducing known complications of the established INFIX or Pelvic Bridge techniques. The complications encompass lateral femoral cutaneous nerve (LFCN) impingement, femoral nerve palsy, spermatic cord compression, heterotopic ossification, and patient discomfort leading to explant and neuropraxia. With regard to the placement of the Bridging Infix, it was hypothesized that structures in the vicinity of the ASIS would be at risk and therefore were considered in the current study. Additional and more pertinent distances to the implant were also needed in order to establish the safety of the Bridging Infix in this reference sample. Currently the LFCN is the most prevalent structure of concern mentioned in publications relating to anterior pelvic fixation. When comparing the Bridging Infix to the established techniques, it was found that the LFCN can be considered to be a safe distance from the cortical screws when they are directly inserted into the iliac crest. The LFCN was found to be a minimum distance of 18.40 mm medial to the most proximal cortical screw. In the current study, no other surrounding anatomical structure, namely the iliohypogastric nerve, ilioinguinal nerve, superficial epigastric vessels, superficial circumflex iliac vessels, femoral vein, femoral artery, femoral nerve or spermatic cord were found to be injured as a result of the implant procedure. Literature has described various surgical risks associated with subcutaneous anterior fixation; which include compression concerns and injury to both the LFCN and femoral nerve. The femoral neurovasculature lie deep to the subcutaneous tunnel and inguinal ligament and are therefore at minimal risk of injury. The closest distance of the femoral nerve to the ASIS was 35.74 mm on the right of one specimen. Anatomical venous variations are known to have a high prevalence and thus are widely reported. During dissection, a unique variation, relating to the course, size, and shape of the superficial external pudendal vein was noted. The superficial external pudendal vein anastomosed on the midline of the anterior abdominal wall and coursed in a tortuous manner across the anterior abdominal wall to the proximal thigh. The diameter of the vessel ranged between 3.01 mm – 7.75 mm which is much larger than reported in literature. Although the variation of the superficial external pudendal vein is an anomaly, surgeons should still be mindful of this during surgical procedures involving the anterior abdominal wall to circumvent bleeding complications.

In conclusion, the Bridging Infix procedure can be considered safe if layer by layer dissection is employed, the screws are directly inserted on the iliac crest, and the musculature is properly retracted during the lateral window dissection, with no pressure being applied within three finger breadths medial to the ASIS. These results are of interest to orthopaedic surgeons operating to reduce pelvic fractures using a minimally invasive technique. These results could assist in reducing post-operative complications following anterior pelvic fixation.