High Accuracy of Three-Dimensional Navigated Kirschner-Wire-Less Single-Step Pedicle Screw System (SSPSS) in Lumbar Fusions: Comparison of Intraoperatively Planned versus Final Screw Position

Abstract

(1) Background: Our team has previously introduced the Single-Step Pedicle Screw System (SSPSS), which eliminates the need for K-wires, as a safe and effective method for percutaneous minimally invasive spine (MIS) pedicle screw placement. Despite this, there are ongoing concerns about the reliability and accuracy of screw placement in MIS procedures without traditional tools like K-wires and Jamshidi needles. To address these concerns, we evaluated the accuracy of the SSPSS workflow by comparing the planned intraoperative screw trajectories with the final screw positions. Traditionally, screw placement accuracy has been assessed by grading the final screw position using postoperative CT scans. (2) Methods: We conducted a retrospective review of patients who underwent lumbar interbody fusion, using intraoperative 3D navigation for screw placement. The planned screw trajectories were saved in the navigation system during each procedure, and postoperative CT scans were used to evaluate the implanted screws. Accuracy was assessed by comparing the Gertzbein and Robbins classification scores of the planned trajectories and the final screw positions. Accuracy was defined as a final screw position matching the classification of the planned trajectory. (3) Results: Out of 206 screws, 196 (95%) were accurately placed, with no recorded complications. (4) Conclusions: The SSPSS workflow, even without K-wires and other traditional instruments, facilitates accurate and reliable pedicle screw placement.

Keywords: 3D-NAV; MIS; MISS; SSPSS; accuracy; minimally invasive; navigation; pedicle screw; screw placement.

Figure 1

Imaging studies of a patient with degenerative spondylolisthesis who underwent minimally invasive TLIF and pedicle screw placement using the SPSS. (A) Lateral X-ray demonstrating L4/5 spondylolisthesis. (B) Sagittal MRI illustrating the left L4/5 foramen. (C) Axial MRI of the L4/5 level shows narrowing of the lumbar spinal canal. (D) Sagittal MRI illustrating the right L4/5 foramen. (E) Coronal postoperative radiograph after L4/5 minimally invasive TLIF. (F) Sagittal postoperative radiograph after L4/5 minimally invasive TLIF.

Figure 2

(A) SSPSS navigated screw inserter with spheres attached, forming the navigation star. The navigation star is crucial for navigation registration and intraoperative anatomical localization. (B) Close-up view of the screw inserter showing the navigated stylet.

Figure 3

Gertzbein and Robbins classification system. (A) 0 mm breach. (B) <2 mm breach. (C) <4 mm breach. (D) <6 mm breach. (E) >6 mm breach.

Figure 4

Lateral, medial, cranial, and caudal screw breaches demonstrated within the vertebral body.

Figure 5

Percutaneous pedicle screw insertion intraoperative imaging. (A) Grade A screw trajectory planned at the right L5 with navigation wand. (B) Final pedicle screw inserted within planned Grade A trajectory at the right L5 pedicle.