Osseous Corridors of the Pelvis: Anatomy and Alternatives

Iliac interosseous corridors are commonly utilized for lag screws or Schanz pins in the fixation of pelvic ring fractures. Numerous such corridors exist. The supraacetabular (SA) corridor extends from the anterior inferior iliac spine to the posterior superior iliac spine. The gluteal pillar extends from the iliac crest toward the acetabulum. The iliac crest osseous corridor is curvilinear and occupies the cranial aspect of the ilium. Though these corridors have been used for the placement of implants up to 7.3 mm, there have not been any studies establishing their exact sizes. This study seeks to define the dimensions and common constriction points of the SA, gluteal pillar, and iliac crest osseous corridors.

Computed tomography scans of 50 male and 50 female hemipelves were evaluated using Philips Brilliance software. The osseous corridor boundaries were determined through manual best-fit analysis. The largest intercortical cylinder within the pathway was measured. Alternative trajectories were tested within the SA and gluteal pillar boundaries to determine if another orientation existed that maximized the intercortical cylinder diameter.

The traditional SA corridor had a mean diameter of 7.8mm in men and 6.3mm in women (p<0.001). A larger alternative SA corridor was found that had a less limited path through the ilium and measured 11.2mm in men and 9.9mm in women. These dimensions are significantly larger compared to those of the traditional SA corridor in both sexes (p<0.001). The gluteal pillar had a mean diameter of 5.6mm in men and 4.7mm in women (p<0.001). No larger, alternative corridors were found. The iliac crest osseous corridor had a mean diameter of 19.5mm in men and 15.9mm in women (p=0.035).

In men, the SA and iliac crest osseous corridors allow for the safe passage of most implants used for pelvic fracture fixation. The gluteal pillar, which is thought to be consistently large, is actually the most limited corridor and usually cannot accommodate implants larger than 5mm in either sex. An alternative SA corridor was found that has a significantly larger mean diameter in both sexes. It is important to keep in mind the limitations of each osseous corridor and to select appropriate implants for each situation.