BISS: concept and biomechanical investigations of a new screw system for electromagnetically induced internal osteostimulation.
BACKGROUND
The aim of an intraosseous application of electromagnetic alternating fields is to speed up both the regeneration of osteonecroses and bone regeneration. In clinical studies, the efficiency of the technique could be successfully proven by using a transducer coil. The advantage of the traditional technique was the variety of its applications in connection with various osteosynthesis systems; the disadvantage was a possible failure of the contacting leads and the resulting functional breakdown.


METHODS
A newly developed BISS screw (bipolar induction screw system) with integrated coil and electrodes was compared to a standard cannulated screw used in the traditional technique. The strength of BISS screws ( n=6) and of cannulated screws ( n=6) was evaluated in comparative biomechanical tests. Examinations consisted of torsional and static and dynamic cantilever tests. All screws were made of the same material (TiAl(6)V(4)) and had identical outer dimensions.


RESULTS
No significantly lower strengths could be observed when we compared BISS screws with cannulated screws. The BISS screws even showed significantly higher mechanical values due to a reinforcing effect by the attached electrode.


CONCLUSIONS
In the modified concept of the new BISS screw, both coil and electrodes are housed in only one cannulated screw. No negative effects concerning mechanical strength and durability were associated with the new screw concept. This provides for a simpler implantation and makes removal easier, while the risk of a cable tear is avoided.
Klinik für Orthopädie und Sportorthopädie, Technische Universität München, Ismaninger Str. 22, 81675, Munich, Germany. wmittelmeier@aol.com
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Mittelmeier
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Lehner
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Kraus
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Matter
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Gerdesmeyer
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Steinhauser
D000497:Alloys; D001696:Biomechanical Phenomena; D001863:Bone Screws; D004566:Electrodes; D004574:Electromagnetic Fields; D006801:Humans; D008422:Materials Testing; D013314:Stress, Mechanical; D014025:Titanium; D014102:Torsion Abnormality
D000497:Alloys; C031462:titanium alloy (TiAl6V4); D014025:Titanium