Indication; Technical Description - miethke THOMALE GUIDE Gebrauchsanweisung

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INDICATION

The THOMALE GUIDE (fi g. 2) is a surgical in-
strument to control the placement of a ventricu-
lar catheter (VC). It is only used as navigation
aid.
Therefore, the following conditions should be
adhered to:
The THOMALE GUIDE is designated for the ap-
plication of a ventricular catheter via a frontal
pre-coronary burrhole. The usage of navigation
devices like the THOMALE GUIDE is advisable
for the implantation of a ventricular catheter.
It is possible that the application of a VC is pos-
sible without the THOMALE GUIDE in case of
enlarged ventricles. It is for the surgeon to de-
cide. In case of narrow ventricles (FOHR-value
smaller than 0.55) the usage of the THOMALE
GUIDE is appropriate. Especially for slit ventri-
cles with a FOHWR-value smaller than 0.05 a
navigation device is recommended.

TECHNICAL DESCRIPTION

The purpose of the VC is to allow the drainage
of cerebrospinal fl uid post surgical placement
into the ventricles. A relevant risk factor for
obstruction of the VC is the non-optimal place-
ment 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 (fi g.1 and fi g. 2).
The THOMALE GUIDE allows a guided punc-
ture of the ventricles with a VC, via a frontal
pre-coronary burrhole, with a relatively low-tech
technique.
* 2008, Huyette, J. et al. „Accuracy of the freehand pass technique for ventriculostomy catheter placement: retro-
spective assessment using computed tomography scans", J Neurosurg 108(1): p.88-91
14
Fig. 1: THOMALE GUIDE with ventricular catheter
Fig. 2: THOMALE GUIDE
It is based on the principle, that in the sagital
plane a right angle to the surface (tangent) al-
ways reaches the ventricles correctly (Fig. 3),
whereas in the coronal plane an individual an-
gle has to be adjusted in order to allow a cor-
rect placement (fi g. 4 and fi g.5). Therefore the
THOMALE GUIDE is placed directly over the
burrhole with its three feet on the skull bones