Preliminary evaluation of mixed reality navigation with single-vertebra registration in spinal surgery

To develop a mixed reality navigation system based on single-vertebra registration and to preliminarily validate its feasibility in clinical surgery, providing a potential reference for spinal surgical navigation registration methods.

We developed a portable, stand-alone, optical-based mixed reality navigation system for spinal surgery using a head-mounted display. The system integrates registration and real-time localization functions, enabling single-vertebra registration via anatomical landmarks and interactive visualization through the HoloLens 2 platform. System performance was evaluated in both laboratory and clinical settings by measuring localization time, fiducial registration error (FRE), and target registration error (TRE). Preoperative assessments were conducted on patient-specific 3D-printed vertebral models, and intraoperative evaluations were performed on exposed vertebrae during surgery. Additional trials with novice surgeons were performed to assess the learning curve. For selected cases requiring pedicle screw placement, surgeons qualitatively evaluated the intraoperative visualization of preplanned screw trajectories in terms of anatomical congruence, feasibility, and display clarity.

A total of 37 spinal surgery patients were included, covering cervical, thoracic, and lumbar segments. The average preoperative navigation time based on 3D-printed models was 2.96 ± 0.26 min, compared with 3.11 ± 0.25 min intraoperatively (p = 0.002). The FRE was 1.37 ± 0.54 mm preoperatively and 1.42 ± 0.52 mm intraoperatively (p = 0.178). The TRE was 1.52 ± 0.56 mm preoperatively and 1.75 ± 0.61 mm intraoperatively (p = 0.001). Among four pedicle screw placement cases, three were rated satisfactory intraoperatively, and one showed an approximately 5 mm deviation due to minor patient positional changes. The learning curve indicated that procedure time stabilized at approximately 2.7 min after about 15 practice cases.

The single-vertebra registration-based mixed reality navigation system enables rapid and accurate vertebral localization in both preoperative and intraoperative settings, with TREs within clinically acceptable limits. The system is portable, easy to operate, and provides an intuitive, immersive navigation interface without relying on external tracking devices. These features suggest its potential as a cost-effective and versatile tool for spinal surgery navigation.