Comparative tomographic study of the S2-alar-iliac screw versus the iliac screw

Abstract

Aims Iliac screws and S2-alar-iliac screws provide adequate mechanical stability for the fixation of lumbosacral spine pathologies, which has led to a significant increase in the use of these techniques in the routine practice of spine surgeons. However, studies on the ideal technical positioning for both techniques are limited. Study design This is an observational, retrospective, analytical descriptive study. Objective To analyze, describe and compare the insertion and positioning parameters of the S2-alar-iliac and iliac screw techniques in adult patients without spinal deformities. Methods The present study comprises a retrospective analysis of lumbosacral computed tomography images selected continuously in 2016 from 25 patients at a university hospital. Mann-Whitney-Shapiro-Wilk tests were performed. Data reliability was assessed using intraclass correlation. Results The mean length of the iliac screw was greater than that of the S2-alar-iliac screw, and the S2-alar-iliac screw sat 20.5 mm deeper than the iliac screw. The mean of the greatest bone thickness for the iliac screw was 20.72 mm; that of the S2-alar-iliac screw was 23.24 mm. The mean distance from the iliac screw entry point to the skin was 32.46 mm, and the mean distance from the S2-alar-iliac screw entry point to the skin was 52.87 mm. Conclusion The trajectory of the S2-alar-iliac screws studied via computed tomography was greater in terms of bone thickness and deeper relative to the skin compared with the iliac screws. The S2-alar-iliac technique may have desirable clinical advantages in terms of the diameter of the screws and reduced protrusion when used in adults. Graphical abstract These slides can be retrieved from Electronic supplementary material.

Intraoperative imaging and navigated spinopelvic instrumentation: S2-alar-iliac screws combined with tricortical S1 pedicle screw fixation

“…However rates of SSI in S2AIS were slightly higher in this study with 9.6% compared to previous reports with SSI rates between 1.5 and 4.5% [9], potentially as a result of a high number of multilevel deformity correction surgeries. Further, the higher rate of SSI following conventional IS implantation could also be explained by the 26% lesser distance of the screw head to the surface of the skin surface in patients with IS, which is in agreement with a previous report [40] and bears the additional risk of a painful posterior iliac prominence [5]. Measures to minimize IS prominence include grafting of an osseous depression [41] and although we did in fact harvest bone at the screw entry point site to better seat the IS before implantation, we failed to achieve a skin distance of the screw head that was comparable to S2AIS, similar to previous reports [29,40].…”

The influence of sagittal profile on the S2 alar-iliac (S2AI) screw trajectory in degenerative lumbar scoliosis patients: A computed tomography (CT) study

“…Although the successful placement of S2AI screw with free-hand technique had been reported, it remained a challenge for spine surgeons since displacement of S2AI screw posed threaten to important neurovascular structures adjacent to pelvis [9][10][11]. Accurate S2AI screw placement depended on proper trajectory angles in both sagittal plane and axial plane.…”

The Influence of Radiographic Parameter on the S2 Alar‐Iliac Screw Virtual Trajectory in Degenerative Lumbar Scoliosis Patients: A Computed Tomography Study

“…The internal iliac artery was at risk of injury from anterior screw perforation while the superior gluteal artery was at risk of injury from caudal screw violation. 9 , 10 , 11 Therefore, surgeons should ensure accurate S2AI insertion to avoid these major vessels injuries, which can be life‐threatening complications.…”

“… 5 , 15 , 16 However, the recommended ideal trajectory angles for S2AI screw placement varied in the literature. 5 , 6 , 9 , 11 , 17 , 18 , 19 The S2AI screw traverse both the ilium and sacrum. Therefore, there is no doubt that the S2AI screw trajectory is influenced by morphological characteristic of pelvis.…”