The THOMALE GUIDE was designed for the precise insertion of a ventricular catheter via a frontal pre-coronary burrhole. It is used together with the THOMALE GUIDE APP for iPhone and iPad as a navigation aid.
A relevant risk factor for obstruction of the VC is the non-optimal placement and contact with adjacent tissue. In the past, catheters were placed mostly free-hand. In the literature it shows, that in more than 40 % of treatments*, an incorrect positioning of the VC can occur. Hence, in recent years X-rays or neuro navigation was needed in order to control the implantation procedure. This means a great technical effort is required for a relatively small surgical intervention. The THOMALE GUIDE was designed for an exact placement of the VC, using a simple technique, to avoid complications.
The THOMALE GUIDE consists of 4 single parts: catheter guide(1), locking nut (2), slider(3), guide rails and base ring (4). The THOMALE GUIDE was designed for the Miethke-VC. For the Miethke-VC only the catheter guide with an inner diameter of 2,6 mm (ID2.6) should be used. Optionally, the THOMALE GUIDE is supplied with catheter guides with an inner diameter of 3,1 mm (ID3.1) and 3,6 mm (ID3.6) so that a range of ventricular catheters with different diameters can be used.
The THOMALE GUIDE allows a guided puncture of the ventricles with a VC, via a frontal pre-coronary burrhole.
The drillholes start 3 mm away from the top and end after 14 mm. This will prevent drainage into the brain from very narrow ventricles during implantation.
It is based on the principle, that in the sagital plane a right angle to the surface (tangent) always reaches the ventricles correctly, whereas in the coronal plane an individual angle has to be adjusted in order to allow a correct
placement. Therefore the THOMALE GUIDE is placed directly over the burrhole with its three feet on the skull bones and with its line markings parallel to the centre line, so that a right angle in the sagittal plane
is guaranteed. In the coronal plane an individual angle can be set with an angle adjustment on the THOMALE GUIDE. The rotation of the catheter guide, which is directed via guide rails, results from a very close fulcrum over the burrhole.
* 2008, Huyette, J. et al. „Accuracy of the freehand pass technique for ventriculostomy catheter placement: retrospective assessment using computed tomography scans“, J Neurosurg 108(1): p.88-91