CT observation of L5 pedicle screw fixation shielding by the iliac wing width and height

Abstract

Objective: The height and width of the iliac wing were measured using three-dimensional computed tomography(3D-CT), and the extent to which the iliac wing occluded the entry point of the 5th lumbar vertebra pedicle screw(L5PS) was observed and graded according to severity. The overall goal was to study the influence of the height and width of the iliac wing on L5PS insertion.

Patients and methods: This study included 350 cases (179 males and 171 females) where the L1-S2 region was obtained. We reconstructed 3D-CT in our study for anatomic analysis. The width and height of the iliac wing were measured on CT axial and oblique sagittal images, respectively. The degree of the L5PS entry point was determined by the data of iliac wing width and height, and divided into 0, I, II and III levels. The association between width and height of the iliac wing among males and females was also analyzed in this paper.

Results: The incidence of shielding of the L5PS entry point by the height and width of the ilium wing were 20.0 % and 19.4 %, respectively. The overall incidence of obstruction of L5PS by the width of the ilium wing was 27.3 % in males and 12.3 % in females. In total, there were 27, 14, and 8 male patients with level I, II, and III shielding, respectively. There were 12, 7, and 2 females with level I, II, and III shielding, respectively. The overall incidence with which the height of the ilium wing obstructed L5PS was 24.0 % in males and 14.6 % in females, of which there were 23 males with level Ⅰ shielding, 16 males with level Ⅱ shielding, 4 males with level Ⅲ shielding, 13 females with level Ⅰ shielding, 8 females with level Ⅱ shielding, and 4 females with level Ⅲ shielding.

Conclusions: The height of the ilium caused obstruction of the L5PS more frequently than the width of the ilium, and males had a higher incidence of iliac wing occlusion than females at both the height and width. The degree of L5PS entry point shielding by the iliac wing width along the horizontal axis was not completely consistent with that of L5PS shielding on the oblique sagittal plane.

Keywords: Iliac wing height; Iliac wing width; The 5th lumbar vertebra pedicle screw; Three-dimensional CT reconstruction.