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Methods: Preclinical studies where performed to compare the adsorption the wire from the ventilation tubes moved during vibration of the Petri dish.
behaviour of titanium, stainless steel and aluminum oxide toward radio- With exception of two implants, all implants changed positions in the water
active marked albumin and native collagen type I. An animal model in the bath. In the swim test, the gold implants showed the least movement of all
rabbit was performed to study the integration of titanium in the middle ear the implants. In this study, the properties of the non-ferromagnetic implant
morphologically. Middle ear prostheses removed during revision surgery materials differed in the 7 Tesla MRI. Stainless steel ventilation tubes, the
were studied as well. trachea support ring and the nose dilatator were not suited for the 7 Tes-
la MRI system, because they changed their position during MRI. In the
Results: Titanium showed an adsorption amount of 360 microgram/cm(2), case of ventilation tubes with a steel wire, the wire should be removed
stainless steel of 230 microgram/cm(2) and aluminum oxide of 500 micro- before MRI to prevent injury to the external auditory canal. There was a
gram/cm(2) out of an albumin solution of 400 mg/ml. Comparing desorption tendency for the pure gold implants to move less in the 7 Tesla MRI than
the mean loss was 16 % for titanium, 21 % for stainless steel and 23 % for al- all other tested materials. General statements cannot be made about the
uminium oxide. Reassembled collagen fibrils could be detected after adsorp- MRI suitability of different implants. Every implant should be individually
tion in collagen type I solution by means of scanning electron microscopy. examined to confirm its definitive MRI compatibility. Particularly, middle
Morphological studies in animal experiments showed regular healing after ear implants warrant special attention here due to their closeness to the
implantation. Explanted prostheses from humans did not show any cellular oval window.
signs of repulsion.
Conclusion: The results of preclinical studies and clinical use demonstrate Safety evaluation of titanium middle ear prostheses at 3.0 tesla
titanium as a useful material for ossicular reconstruction in middle ear
surgery. Martin A. D., Driscoll C. L., Wood C. P., Felmlee J. P.

Published: Otolaryngol Head Neck Surg 2005 Apr;132(4):537-42.
Titanium as an ossicular replacement material: results after
336 days of implantation in a rabbit Objective: To assess the magnetic resonance imaging (MRI) safety of tita-
nium middle ear prostheses at 3.0 tesla (T).
Schwager K.
Study Design and Setting: Titanium middle ear prostheses from 3 com-
Published: Am J Otol. 1998 Sep; 19(5):569-73 mercial vendors were examined for magnetic field interactions at 3 T.
Initially, ex vivo studies were performed to test for rotational motion and
Objective: Titanium in other parts of the body, well known for its biocom- forward displacement (translational motion) of the prostheses in a static
patibility, was examined in an animal model for its use as an ossicular re- magnetic field. If movement was observed during this screening study, then
placement material. the prosthesis was tested to determine the translational or rotational force
acting upon the prosthesis. In addition to testing for prosthesis displace-
Study Design: The biocompatibility of titanium was studied in the middle ment, temperature changes of the prostheses were measured to assess for
ear of rabbits using light and scanning electron microscopy. Titanium pins radiofrequency heating during imaging.
were placed as middle ear prostheses or as free implants and were examined
after 28, 84, 168, and 336 days. Results: Twenty-one of the 24 titanium prostheses tested revealed no move-
ment when tested in the 3 T static magnetic field. Three prostheses revealed
Results: After 28 days, the prostheses were covered by regular mucosa. The minimal movement during the screening study. A translational force test
free implants took up to 336 days to be totally epithelialized. There were no (string test) was performed upon these 3 prostheses, and the measured an-
inflammatory cells observed on the surface of the material nor were unusual gle of displacement was used to determine the force. This calculated force
amounts of fibrous tissue seen. In addition, the titanium material exhibited acting upon each prosthesis was essentially zero. Therefore, we conclude
an affinity toward bone. that the magnetic field interaction is negligible. A positive control with a
ferromagnetic stainless steel prosthesis demonstrated obvious displacement
Conclusions: The results of this animal experiment indicate that titanium is during the screening study, as well as deflection of the prosthesis by 90 de-
a useful material for ossicular replacement prostheses. grees in the translational force test. Last, heating of the titanium prostheses
did not occur in the 7 models tested.
Conclusions: Middle ear prostheses made from titanium are safe,
MRI neither deflecting nor heating during magnetic resonance examinations
conducted at 3 T.
Behavior of metal implants used in
ENT surgery in 7 Tesla magnetic resonance imaging
COUPLING OSSICUL OPL A S TY
Thelen A., Bauknecht H. C., Asbach P., Schrom T.
Published: Eur Arch Otorhinolaryngol. 2006 Oct;263(10):900-5. Coupling problems in middle ear reconstruction
DOI: 10.1007/s00405-006-0082-2
Zahnert T.
Magnetic resonance imaging (MRI) has become increasingly important as
an imaging technique in cross-sectional imaging of head and neck diseases. Published: MEMRO 2006, 4th International Symposium on Middle Ear
To investigate whether MRI examinations can be performed without risk in Mechanics in Research and Otology: Selected Abstracts.
patients with metal implants even at higher field strengths, we examined
different materials in 7 Tesla MRI. Implants near sensory organs like the The normal and reconstructed middle ear can be considered as a mechani-
middle ear or eye are of particular interest here. Using the 7 Tesla research cal vibrating system. After the implementation of tympanoplasty as a stan-
MRI for small animals, we tested implants made of various metals like dardized surgical technique various reconstruction techniques and implants
titanium, gold, gold/platinum, platinum/iridium, gold-plated silver, PTFE were suggested for the reconstruction of the tympanic membrane and the
and stainless steel for heating, translocation and rotation according to a ossicular chain. Laser–Doppler-vibrometry and model calculations have
standardized protocol. A fiber optic temperature probe measured the heat- given new insight into the vibration modes of the normal and reconstructed
ing of the implant before, during and after MRI scanning. None of the im- middle ear during the recent years. Nowadays it can be concluded, that
plants showed significant heating. The gold-plated stainless steel ventilation not only material properties of implants but also coupling factors have an
tube was the only implant to markedly change its position already in the Petri important influence on good hearing results. We investigated coupling fac-
dish. Of the remaining implants, a trachea support ring, a nose dilatator and tors between tympanic membrane and the surrounding bone, between the

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