Artikel
Electromagnetic transcutaneous induction heating of an intramedullary nickel titanium shape memory material implant
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Autoren
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C.W. Müller
- Medizinische Hochschule Hannover, Unfallchirurgische Klinik, Hannover, Germany
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T. El-Kashef
- Medizinische Hochschule Hannover, Unfallchirurgische Klinik, Hannover, Germany
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R. Pfeifer
- Laser Zentrum Hannover, Hannover, Germany
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K. Klix
- Medizinische Hochschule Hannover, Unfallchirurgische Klinik, Hannover, Germany
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C. Krettek
- Medizinische Hochschule Hannover, Unfallchirurgische Klinik, Hannover, Germany
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T. Gösling
- Medizinische Hochschule Hannover, Unfallchirurgische Klinik, Hannover, Germany
| Veröffentlicht: | 18. Oktober 2011 |
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Gliederung
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Questionnaire: Fracture healing depends on both biological properties, such as blood supply, cellular immune response, availability of osteoinductive cytokines, and biomechanical stimuli. Shape memory orthopaedic implants made from nickel-titanium (NiTi) might allow modulating fracture healing, changing their cross-sectional shape by employing the shape memory effect, and thereby changing their stiffness. This study aims to show the feasibility and safety of contact-free electromagnetic induction heating of an intramedullary NiTi implants in a rat model.
Methods: A water cooled generator-oscillator combination (“inductor”) was used. Induction characteristics were determined by measuring the temperature increase of a test sample in correlation to generator power and time. In 50 rats, the right knee was exposed and an intercondylary approach was used to introduce a cylindrical NiTi implant, which was connected with a temperature probe, into the femur. The animals were transferred to the inductor, and the implant was electromagnetically heated to temperatures between 40° and 60°C to test potential temperatures needed to exhibit the shape memory effect (Figure 1 [Fig. 1]).
Blood samples were drawn before and 4 hours after the procedure. IL-1, IL-4, IL-10, TNF-α, and IFN-γ were measured. Animals were sacrificed at 3 weeks. Histological specimens from the hind leg and liver were retrieved and examined for inflammatory changes, necrosis, and corrosion pits.
Results and Conclusions: Induction characteristics were almost equal to previous results from heat induction of submuscular NiTi implants. Cytokine measurements and histological specimens showed no significant differences among the groups. No necrosis was found. All liver specimens were scored 0 for no signs of inflammation, all sections from the femur were scored with either no or mild signs of imflammation. No corrosion pits were found.
We conclude that contact-free electromagnetic induction heating of an intramedullary NiTi implant in a rat model up to 60°C is feasible and safe. This enables us to carry on in the development of more functional orthopaedic shape memory NiTi implants.
