Article
Accuracy of 2D-3D Fluoro-CT-matching for spinal navigation: a laboratory investigation with comparison to standard matching techniques
Akkuratesse des 2D-3D Fluoro-CT-matching für die spinale Navigation: eine In-vitro Untersuchung mit Vergleich zu Standard-Matchingtechniken
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Outline
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Objective
Although still controversial, spinal navigation is used increasingly as an adjunct in more complex spinal surgical cases. Different matching procedures have been introduced over time with the surface matching technique being the method most widely used. For percutaneous spinal procedures, however, surface matching is not available and virtual fluoroscopy is frequently used as an alternative which relies on only twodimensional image guidance with several drawbacks. Automated Fluoro-CT-matching, which coregistrates intraoperative fluoroscopic views with preoperative CT scans, is overcoming these drawbacks. Accuracy of this technique is rarely reported to date and a comparison with other matching techniques has not been done so far.
Methods
Investigations were performed with the vectorvision spine system (BrainLab, Heimstetten, Germany). Using a plastic vertebra model (sawbones), multiple transpedicular pilot holes were drilled with a 3,2 mm burr. CT scanning was then performed and the data set was prepared for comparative measurements of different matching techniques. The pilot holes and their coordinates were used as targets. Using the integrated “autopilot” function of the navigation system comparisons of accuracy were made for paired point matching, surface matching and Fluoro-CT-matching, respectively.
Results
Mean translatory accuracy was 0,38 mm (±0,62mm, 95% confidence intervall) for Fluoro-CT-matching compared to 0,88 mm (±0,83mm) and 3mm(±2,72 mm) for surface matching and paired point matching, respectively. Mean rotatory accuracy was 0,63° (±0.99°, 95% confidence intervall) for Fluoro-CT-matching compared to 0,75° (±1,24°) and 3,13° (±2,47°) for surface matching and paired point matching, respectively. Univariate analysis for both measurements depicted that the differences were significant (p=0,037).
Conclusions
Among the available matching techniques, Fluoro-CT-matching is the most accurate. Its properties include the use in percutaneous spinal procedures which make this technique even more attractive. Nevertheless, accuracy of a matching technique is only a part of all caveats that have to be taken into account using computer guidance in surgery.
