Article
Revisiting the rules for freehand ventriculostomy: a virtual reality analysis
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Authors
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Jens Fichtner
- Inselspital, Universitätsspital Bern, Universitätsklinik für Neurochirurgie, Bern, Schweiz
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Clemens Raabe
- Inselspital, Universitätsspital Bern, Universitätsklinik für Neurochirurgie, Bern, Schweiz; Inselspital, Universitätsspital Bern, Universitätsinstitut für Diagnostische und Interventionelle Neuroradiologie, Bern, Schweiz
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Jürgen Beck
- Inselspital, Universitätsspital Bern, Universitätsklinik für Neurochirurgie, Bern, Schweiz
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Jan Gralla
- Inselspital, Universitätsspital Bern, Universitätsinstitut für Diagnostische und Interventionelle Neuroradiologie, Bern, Schweiz
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Andreas Raabe
- Inselspital, Universitätsspital Bern, Universitätsklinik für Neurochirurgie, Bern, Schweiz
| Published: | June 18, 2018 |
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Outline
Text
Objective: Frontal ventriculostomy is one of the most frequent and standardized procedures in neurosurgery. However, many first and subsequent punctures miss the target, and suboptimal placement or misplacement of the catheter is common. We therefore re-examined the landmarks and rules to determine the entry point and trajectory with the best hit rate (HtR).
Methods: Computed tomography scans of 50 patients with normal ventricular and skull anatomy, and without ventricular puncture were selected. Using a 5 x 5 cm frontal grid with 25 entry points referenced to the bregma, we examined trajectories 1) perpendicular to the skull, 2) towards classical facial landmarks in the coronal and sagittal plane and 3) towards an idealized target in the middle of the ipsilateral anterior horn. Three-dimensional (3D)-virtual reality ventriculostomies were performed for these entry points and trajectories and the HtRs were recorded, resulting in an investigation of 8000 different virtual procedures.
Results: The best HtR for the ipsilateral anterior horn (ILAH) was 86% for an ideal trajectory, 84% for a landmark trajectory, and 83% for a 90° trajectory, but only at specific entry points. The highest HtRs were found for entry points 3 or 4 cm lateral to the midline, but only in combination with a trajectory towards the contralateral canthus, and 1 or 2 cm lateral to the midline, but only paired with a trajectory towards the nasion. The same "pairing" exists for entry points and trajectories in the sagittal plane. For perpendicular (90°) trajectories, the best entry points were at 3–5 cm lateral to the midline and 3 cm anterior to the bregma, or 4 cm lateral to the midline and 2 cm anterior to the bregma.
Conclusion: Only a few entry points offer a chance of >80% of hitting the ILAH, and then only in combination with a specific trajectory. This "pairing" between entry point and trajectory was found both for landmark targeting and for perpendicular trajectories, with very limited variability. Surprisingly, the ipsilateral medial canthus (IMC), a commonly quoted landmark, had low HtRs and should not be recommended as a trajectory target.
