The iliac kickstand screw: anatomic CT analysis of screw trajectory and osseous corridor for screw placement

Abstract

IntroductionThe ‘kickstand screw-rod’ technique has been recently described for correction of coronal malalignment. This technique utilizes powerful ‘construct-to-ilium’ distraction between a fixed multi-screw thoracic construct and the ilium, facilitated by a novel ‘iliac kickstand screw’. The ‘iliac kickstand screw’ traverses a previously undescribed osseous corridor in the ilium.ObjectiveUsing a radiographic CT study, the objective is to describe a large osseous corridor within the ilium to accommodate the novel iliac kickstand screw.Methods50 consecutive patients with pelvic CTs at an academic medical center were queried. Simulated iliac kickstand screw trajectories for the left and right hemipelvis were analyzed with 3D visualization software. Maximal screw lengths and dimensions, and trajectories in the osseous corridor were measured.Results50 patients’ (31 female, 19 male) pelvic CTs were measured with a total of 100 simulated screws. The mean age was 52.4 years and BMI 28.1 ± 7.9. The average length is 119.7 ± 6.6 mm (range 98.7 − 135.3). The narrowest width (maximum potential screw diameter) is 17.8 ± 2.9 mm (coronal) and 20.8 ± 5.3 mm (sagittal). The starting point to the top of the iliac crest is 66.4 mm lateral to midline, and 15.9° caudal in the sagittal and 6.1° lateral in the coronal planes.ConclusionsThe novel iliac kickstand screw traverses a consistent and large osseous corridor within the ilium. The average simulated screw length is 119.7 mm and maximum potential diameter of 17.8 mm. Starting points relative to the iliac crest are identified.