Navigated pedicle screw placement: experimental comparison between CT- and 3D fluoroscopy-based techniques.
OBJECTIVE
Even with CT-based navigation, the misplacement rate for pedicle screws is reported to be as high as 10%. Using fluoroscopy-based 3D navigation, misplacement rates of 1.7 to 6% occur. The purpose of this study was to compare the accuracy of CT-based and Iso-C-based navigation in an experimental context.


METHODS
A foam spine model and the SurgiGATE navigation system were used. First, a determination of point accuracy measured the difference between the real positions of markers placed on selected vertebrae and their positions as determined by the navigation system. In the verification mode, the pointer is placed exactly on the markers displayed on the monitor screen, and the deviation of the pointer tip and marker is measured in reality using a caliper. Secondly, pedicle accuracy was measured using pre-drilled holes for pedicle screws. A trajectory was planned into the visible hole and the navigated pointer was placed.


RESULTS
The measured accuracy for the markers showed a statistically significant difference between the results with CT and Iso-C navigation for one of six markers placed on the vertebra. Iso-C-based navigation demonstrated a lower mean deviation of 0.5 mm, compared to 1 mm with CT-based navigation. The deviation within the pre-drilled holes was lower when using the Iso-C3D scan. Using Iso-C3D navigation, 76.6% of the measurements showed no deviation at the entrance point, compared with 43% when using CT-based navigation. Also, with Iso-C3D navigation, 78.3% of the inserted pedicle awls hit the defined trajectories in the pre-drilled holes correctly, compared to 66.6% with CT-based navigation.


CONCLUSIONS
The overall image-to-reality accuracy for CT- and Iso-C-based navigation was assessed in the described experimental setup. An apparent tendency towards higher accuracy with Iso-C-based navigation was evaluated; however, the differences were not significant.
Geerling
Jens
J
Trauma Department, Hannover Medical School, Hannover, Germany.
Gösling
Thomas
T
Gösling
Anna
A
Ortega
Gil
G
Kendoff
Daniel
D
Citak
Musa
M
Krettek
Christian
C
Hüfner
Tobias
T
D001863:Bone Screws; D005240:Feasibility Studies; D005471:Fluoroscopy; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation*; D013122:Spinal Diseases / Q000601:surgery*; D013131:Spine / Q000601:surgery*; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed