Digital Reference Frame Anchored to the Pedicle Screw–rod Construct for O-arm–Assisted Pedicle Screw Insertion: A Pilot Study

Abstract

Objective: Accurate pedicle screw placement reduces neurological injury and complications. Although O-arm navigation improves precision, navigation error and digital reference frame (DRF) instability persist. This study aims to develop and evaluate a novel DRF anchored to the pedicle screw-rod construct as an alternative to spinous process-based attachment for O-arm-assisted pedicle screw insertion. Materials and Methods: This pilot study enrolled patients undergoing O-arm-assisted thoracolumbar pedicular screw instrumentation between November 2024 and February 2025. At each instrumented level, one pedicle screw was placed using the conventional DRF, and the contralateral pedicle screw was placed using the novel pedicle screw-rod-anchored DRF. We compared the 2 DRF systems within each level. Navigational error was defined as the angular deviation between the intraoperative virtual trajectory and the screw position on postoperative computed tomography. Pedicle breaches were identified and graded. Results: Twenty-two patients (110 pedicle screws) were included. The median navigational error did not differ between novel and conventional DRF in axial (2°, P = 0.500) or sagittal (2°, P = 0.070) planes. Subgroup analyses by level and pathology (degenerative, tumor, trauma) showed no significant differences. Minor pedicle breaches (< 2 mm) occurred in 2 screws with the novel DRF and 3 screws with the conventional DRF, all mid-thoracic and without clinical complications. Conclusions: The novel pedicle screw-rod-anchored DRF provides navigational accuracy comparable to the conventional system. These findings support its feasibility as an alternative reference frame for O-arm-guided spinal procedures when spinous process fixation is limited.