Feasibility of magnetic activation of a maxillofacial distraction osteogenesis, design of a new device.
OBJECTIVE
Distraction osteogenesis is a technique of bone lengthening which uses the bone's natural healing process. Current devices for craniofacial distraction require a transmucosal or transcutaneous activator and are associated with numerous complications. The aim of this study was to evaluate the feasibility of a rodless magnetic activation device that could be used in craniofacial distraction.


METHODS
The method is based on the torque applied between two unaligned permanent magnets. This torque depends on magnet size, shape, composition, magnetization and distance between the two magnets. Using a configuration close to that which would be applied in actual distraction osteogenesis (in terms of the distance between the two magnets), we performed an analytical study and evaluated the results.


RESULTS
We observed good agreement between the model and the experimental results, finding that the transmitted force value is comparable to the force required in mandibular distraction. Thus, we proposed a design of a new distracting device consisting of a cylindrical permanent magnet diametrically magnetized and fixed to an endless screw along its main axis. Activation of the distraction motion is achieved through interaction of the first magnet with a second cylindrical magnet whose magnetization is orthogonal to its main axis and to the device's endless screw.


CONCLUSIONS
This preliminary study demonstrates that magnetic activation for mandibular osteogenic distraction is feasible and that device size is not a constraint. We propose a prototypic device.
ENSTA Paris-Tech, Department of Mechanical Engineering, Palaiseau, France.
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J
Boisson
Ecole Polytechnique, Palaiseau, France.
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H
Strozyk
APHP, Necker Enfant Malades, Unit of Maxillofacial and Plastic Surgery, Paris, France; Maxillofacial Malformation Reference Center (MAFACE), Paris, France.
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P
Diner
APHP, Necker Enfant Malades, Unit of Maxillofacial and Plastic Surgery, Paris, France; Maxillofacial Malformation Reference Center (MAFACE), Paris, France; Paris Descartes University, Paris, France.
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A
Picard
APHP, Necker Enfant Malades, Unit of Maxillofacial and Plastic Surgery, Paris, France; Maxillofacial Malformation Reference Center (MAFACE), Paris, France; Paris Descartes University, Paris, France. Electronic address: natacha.kadlub@aphp.fr.
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N
Kadlub
D005240:Feasibility Studies; D006801:Humans; D008280:Magnetics / Q000295:instrumentation*; D008334:Mandible / Q000601:surgery; D008962:Models, Theoretical; D056948:Orthognathic Surgical Procedures / Q000295:instrumentation / Q000379:methods*; D019857:Osteogenesis, Distraction / Q000295:instrumentation / Q000379:methods*; D019415:Torque
Distant activated distractor device; Distraction osteogenesis; Hemifacial microsomia; Magnetic field