A novel approach to navigated implantation of S-2 alar iliac screws using inertial measurement units

Abstract

<jats:sec> <jats:title>OBJECT</jats:title> <jats:p>The authors report on a novel method of intraoperative navigation with inertial measurement units (IMUs) for implantation of S-2 alar iliac (S2AI) screws in sacropelvic fixation of the human spine and its application in cadaveric specimens.</jats:p></jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>Screw trajectories were planned on a multiplanar reconstruction of the preoperative CT scan. The pedicle finder and screwdriver were equipped with IMUs to guide the axial and sagittal tilt angles of the planned trajectory, and navigation software was developed. The entry points were chosen according to anatomical landmarks on the exposed spine. After referencing, the sagittal and axial orientation of the pedicle finder and screwdriver were wirelessly monitored on a computer screen and aligned with the preoperatively planned tilt angles to implant the S2AI screws. The technique was performed without any intraoperative imaging. Screw positions were analyzed on postoperative CT scans.</jats:p></jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>Seventeen of 18 screws showed a good S2AI screw trajectory. Compared with the postoperatively measured tilt angles of the S2AI screws, the IMU readings on the screwdriver were within an axial plane deviation of 0° to 5° in 15 (83%) and 6° to 10° in 2 (11%) of the screws and within a sagittal plane deviation of 0° to 5° in 15 (83%) and 6° to 10° in 3 (17%) of the screws.</jats:p></jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>IMU–based intraoperative navigation may facilitate accurate placement of S2AI screws.</jats:p></jats:sec>

Extra-articular Portion of the Sacroiliac Joint—Between the Sacral and Pelvic Tuberosities: An Anatomical Guide for the S2-Alar-Iliac Screw Trajectory

“…Navigation software is not only able to simulate whether the S2AI screw can be inserted, but also is able to detect lumbosacral transitional vertebrae. 18,19 As shown in Figure 4, the use of navigation software is particularly helpful for Castellvi III cases.…”

Reproducibility of S2-Alar Iliac Screw Morphometric Analysis

“…The point of entry considered was the midpoint of the posterior cortical of the sacrum between the foramens of S1 and S2. 3,13 Still in the oblique axial plane, the LL and the SL of the screw were measured (Figure 4), tangentially the internal and external corticals of the iliac, respectively; the largest viable DIAM of the screw, which corresponds to the smallest measure of the virtual space between the inner and outer tables of the iliac (Figure 4); and the ATAs (ATALL and ATASL) in relation to the anteroposterior line, perpendicular to the horizontal line of the pelvis (Figure 5). Knowing that the diameter of the implants is determined by the measurement of the internal screw size, 3.75 mm (half of the diameter of the chosen implant (7.5mm)) was subtracted medially and laterally so that the screw threads do not violate the iliac bone corticals (Figure 6).…”

Rigid and non-rigid motion compensation in weight-bearing cone-beam CT of the knee using (noisy) inertial measurements

“…In C-arm CT, inertial measurement units (IMUs) containing an accelerometer and a gyroscope have until now been applied for navigation [15] and calibration [18] purposes. Our recent work was the first to propose the use of IMUs for motion compensation in weight-bearing cone-beam CT (CBCT) of the knee [22].…”