Monitoring image guidance system accuracy during spinal surgery with mini-screw fiducials: Technical note

STUDY DESIGN: A technical note. OBJECTIVE: To describe a technique for measuring accuracy of intraoperative image guidance systems in spine surgery. SUMMARY OF BACKGROUND DATA: Image guidance may be of use when performing complex procedures on the spine. However, as the operation progresses and, in particular, once any deformity has been corrected, the image guidance system may become unreliable. In practice, this often results in repeated image acquisitions thus increasing the radiation exposure to the patient. METHODS: Small titanium, cranio-facial screws were placed on the dorsal aspect of the spine intraoperatively, before the acquisition of images and used as fiducials. RESULTS: The authors were able to accurately discern the true precision of the image guidance system used with an intraoperative computed tomography scanner, throughout the procedure. CONCLUSIONS: By using intraoperatively placed mini-screw fiducials, the surgeon may check and quantify the underlying system accuracy both initially and throughout the surgery. In the future, "auto-adjust" functions may be integrated into the computer software to automatically recalibrate the system when a probe is placed into the fiducials without the need for rescanning.