Defining the Iliac Wing Osseous Fixation Pathways: Anatomy and Implant Constriction Points
Description
Computed tomography scans of 100 male and 100 female hemipelves were evaluated. The iliac wing was studied using manual best-fit analysis of the bounds of the inner and outer cortices. The IOTC was defined as the location of the iliac wing with an intercortical width less than 5 mm. The shortest distance from the apex of the iliac crest to the superior border of the IOTC was defined as the iliac wing osseous corridor. Finally, the width of the gluteal pillar corridor from the gluteus medius tubercle to the ischial tuberosity was measured. The IOTC is an elliptical area measuring 22.3 cm 2 . All ilia had an area where the inner and outer cortices converged to an intercortical width of less than 5 mm; 48% converged to a single cortex. The shortest mean distance from the superior edge of the iliac crest to the beginning of the IOTC was 20.3 mm in men and 13.8 mm in women (p<0.001). The gluteal pillar diameter averaged 5.3 mm in men and 4.3 mm in women (p<0.001). A 4.5 mm iliac wing lag screw will not breach the cortex if it remains within 20 mm or 14 mm distal to the cranial aspect of the iliac crest in males and females, respectively. Not only is the gluteal pillar smaller than previously thought, in some patients it may not be large enough for most implants. Overall, our findings provide improved understanding of the limits for implant use in the iliac wing as well as