An individually mouldable surgical targeting system


Minimally invasive cochlear implant surgery (minCIS) requires appropiate surgical tools to drill a single bore hole from outside the skull directly down to the basal turn of the cochea. Recently, we introduced a new concept for providing a customized surgical targeting system, also known as "micro-stereotactic frame" (MSF) or surgical template. Main idea is to utilize bone cement to fix the individual pose of the template according to a previosly planned trajectory using individual images (e.g. CT or CBCT).

Pictures showing an early prototype of the GluingJig

In a preliminary study, 18 samples of the surgical template were fabricated and evaluated regarding positioning accuracy. The mean positioning error at the target point (located in a depth of approx. 70 mm) was 0.30 mm with a standard deviation of 0.25mm [Rau et al. 2017].

In 2018 we were able to demonstrates the feasibility of performing the minimally invasive access to the middle ear in a proof-of-concept study using the GluingJig surgical targeting system [Rau et al. 2018c]. In that study, the system was evaluated for the first time in a human cadaver trial. After screwing the reference frame ("Trifix") on one temporal bone specimen, a trajectory through the facial recess was planned after imaging. Using that plan the surgical template was composed utilizing bone cement and equipped with a linear guide for the surgical drill. After harding of the bone cement the template was mounted on top of the reference frame and used for drilling into the mastoid as previously planned. Facial nerve and chorda tympani could be preserved. The deviation between the actual drill hole and the planned trajectory was 0.17 mm at the level of the facial recess. The minimal distance of the drill hole to the facial nerve was 0.59 mm.

The proposed system should enable the patient specific fabrication of the instrument guide under sterile conditions. It does not require expensive equipment or technical personal. The whole process can be performed by OR staff in few minutes. These are advantages compared to previously developed systems and might facilitate its integration into clinical routine.

For more information about a first prototype of the GluingJig surgical targeting system please download the Flyer. A German version of the flyer is available here.


If you are interested in this technology, want to join a collaboration for further development, or just have additional questions please do not hesitate to contact:

Dr.-Ing. Thomas Rau


German Research Foundation (DFG, RA 2751/4-1, Title: "Investigation of methods and materials for individually mouldable micro-stereotactic frame", since March 1st 2020).

Preliminary work was supported by the start-up grant for young researches 'HiLF' of Hannover Medical School (2016-2018).


  • European patent granted in 2017 and validated in DE, FR, GB, CH, NL: Rau Th. S., Majdani O., Lenarz T., Kahrs L. A.: Surgical guidance device and method for its preparation. EP 3 058 890 B1. [ Patent].
  • US patent granted in 2019. US 10,441,377 B2 [ Patent].

Further Reading:

Rau Th. S., Zuniga M. G., Salcher R., Lenarz Th. (2020d): A simple tool to automate the insertion process in cochlear implant surgery. Int J CARS 5(11):1931-1939. [ doi].
Rau Th.S., Witte S., Uhlenbusch L., Lexow J., Hügl S., Kahrs L. A., Majdani O., Lenarz T. (2018c): Minimally invasive mastoidectomy approach using a mouldable surgical targeting system. [ doi].
Rau Th., Uhlenbusch L., Witte S., Lexow J., Kahrs LA, Lenarz Th., Ortmaier T., Majdani O. (2018b): Determination of error sources and values for an individually mouldable surgical targeting system. In Proc. 32nd International Congress and Exhibition on Computer Assisted Radiology and Surgery (CARS), June 20-23, Berlin, Germany. [ doi].
Rau Th. S., Lexow G. J., Blume D., Kluge M., Lenarz Th., Majdani O. (2017): Micro-stereotactic frame utilizing bone cement for individual fabrication. An initial investigation of its accuracy. In Proc. SPIE Medical Imaging 2017: Image-Guided Procedures, Robotic Interventions, and Modeling, 101350P. [ doi].
Rau Th. S., Lexow G. J., Kluge M., Lenarz Th., Majdani O. (2016): An alternative concept for template-guided minimally-invasive cochlear implantation surgery. In: Ansó J. et. al (Hrsg.): Proc. 15th Annual Meeting German Society for Computer- and Robot-Assisted Surgery (CURAC), 29.09.-01.10.2016, Bern. Seiten 149-154. [ doi].

About The VIANNA research team