External heating of stents by radio waves

Levitt, Adam; Robinson, Keith A.; Chronos, Nicolas; Daum, Wolfgang

doi:10.1016/s1522-1865(03)00166-5

Cited by 19 publications

(18 citation statements)

References 21 publications

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“…There are precedents for studying AMF exposures as a method for heating implanted metallic objects in applications including tissue hyperthermia 37 , shape-memory alloys 38 , or hyperthermia of intravascular stents 39 . Recently, Coffel and Nuxol 24 proposed a similar concept in which magnetite nanoparticle composite coatings could be used to render a medical implant responsive to an AMF to treat biofilm with heat, although these coatings may not be required when dealing with bulk metal implants.…”

Section: Introductionmentioning

confidence: 99%

Employing high-frequency alternating magnetic fields for the non-invasive treatment of prosthetic joint infections

Chopra

Shaikh

Chatzinoff

et al. 2017

Sci Rep

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Treatment of prosthetic joint infection (PJI) usually requires surgical replacement of the infected joint and weeks of antibiotic therapy, due to the formation of biofilm. We introduce a non-invasive method for thermal destruction of biofilm on metallic implants using high-frequency (>100 kHz) alternating magnetic fields (AMF). In vitro investigations demonstrate a >5-log reduction in bacterial counts after 5 minutes of AMF exposure. Confocal and scanning electron microscopy confirm removal of biofilm matrix components within 1 minute of AMF exposure, and combination studies of antibiotics and AMF demonstrate a 5-log increase in the sensitivity of Pseudomonas aeruginosa to ciprofloxacin. Finite element analysis (FEA) simulations demonstrate that intermittent AMF exposures can achieve uniform surface heating of a prosthetic knee joint. In vivo studies confirm thermal damage is confined to a localized region (<2 mm) around the implant, and safety can be achieved using acoustic monitoring for the presence of surface boiling. These initial studies support the hypothesis that AMF exposures can eradicate biofilm on metal implants, and may enhance the effectiveness of conventional antibiotics.

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Section: Introductionmentioning

confidence: 99%

Employing high-frequency alternating magnetic fields for the non-invasive treatment of prosthetic joint infections

Chopra

Shaikh

Chatzinoff

et al. 2017

Sci Rep

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“…The induction coil was made of three copper windings with an inner diameter of 150 mm leaving enough room to place a rabbit's hind leg inside the coil. As before, a frequency of 250 kHz was used to minimize the impact of the electromagnetic field on biological tissue [ 33 , 34 ].…”

Section: Methodsmentioning

confidence: 99%

A Novel Shape Memory Plate Osteosynthesis for Noninvasive Modulation of Fixation Stiffness in a Rabbit Tibia Osteotomy Model

Müller

Pfeifer

Meier

et al. 2015

BioMed Research International

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Nickel-titanium shape memory alloy (NiTi-SMA) implants might allow modulating fracture healing, changing their stiffness through alteration of both elastic modulus and cross-sectional shape by employing the shape memory effect (SME). Hypotheses: a novel NiTi-SMA plate stabilizes tibia osteotomies in rabbits. After noninvasive electromagnetic induction heating the alloy exhibits the SME and the plate changes towards higher stiffness (inverse dynamization) resulting in increased fixation stiffness and equal or better bony healing. In 14 rabbits, 1.0 mm tibia osteotomies were fixed with our experimental plate. Animals were randomised for control or induction heating at three weeks postoperatively. Repetitive X-ray imaging and in vivo measurements of bending stiffness were performed. After sacrifice at 8 weeks, macroscopic evaluation, µCT, and post mortem bending tests of the tibiae were carried out. One death and one early implant dislocation occurred. Following electromagnetic induction heating, radiographic and macroscopic changes of the implant proved successful SME activation. All osteotomies healed. In the treatment group, bending stiffness increased over time. Differences between groups were not significant. In conclusion, we demonstrated successful healing of rabbit tibia osteotomies using our novel NiTi-SMA plate. We demonstrated shape-changing SME in-vivo through transcutaneous electromagnetic induction heating. Thus, future orthopaedic implants could be modified without additional surgery.

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“…3). Frequencies between 200 and 300 kHz have been used for heating stents 17, 18. Our induction device was set to a frequency of 250 kHz, which proved to be feasible for heating different specimens as NiTi wires and plates.…”

Section: Methodsmentioning

confidence: 99%

Electromagnetic induction heating of an orthopaedic nickel–titanium shape memory device

Müller

Pfeifer

El-Kashef

et al. 2010

Journal Orthopaedic Research

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Shape memory orthopaedic implants made from nickel-titanium (NiTi) might allow the modulation of fracture healing, changing their cross-sectional shape by employing the shape memory effect. We aimed to show the feasibility and safety of contact-free electromagnetic induction heating of NiTi implants in a rat model. A water-cooled generator-oscillator combination was used. Induction characteristics were determined by measuring the temperature increase of a test sample in correlation to generator power and time. In 53 rats, NiTi implants were introduced into the right hind leg. The animals were transferred to the inductor, and the implant was electromagnetically heated to temperatures between 40 and 60 • C. Blood samples were drawn before and 4 h after the procedure. IL-1, IL-4, IL-10, TNF-␣, and IFN-␥ were measured. Animals were euthanized at 3 weeks. Histological specimens from the hind leg and liver were retrieved and examined for inflammatory changes, necrosis, and corrosion pits. Cytokine measurements and histological specimens showed no significant differences among the groups. We concluded that electromagnetic induction heating of orthopedic NiTi implants is feasible and safe in a rat model. This is the first step in the development of new orthopedic implants in which stiffness or rigidity can be modified after implantation to optimize bone-healing. © Keywords: shape memory alloy; fracture healing; rat model; NiTi; electromagnetic induction Nickel-titanium (NiTi) shape memory alloys (SMAs) were described as early as 1963. 1 NiTi medical devices have shown great mechanical strength and biocompatibility in vitro and in vivo, and exhibit pseudoelasticity and shape memory effects. 2 Thus far, clinical applications have comprised stents in vascular surgery and gastroenterology, 3 wires and brackets in orthodontic surgery, 4,5 porous implants in intervertebral body fusion, 2 and staples in foot surgery. 6 The shape memory effect is based on a reversibly martensitic phase transformation. Cooling the parent phase austenite to a critical temperature M s (martensite start temperature) causes the monocrystalline structure to transform to twinned martensite. This transformation is finished by reaching the martensite finish temperature (M f ). In this state, the martensite can be mechanically deformed; the maximum reversible deformation (ε) is 8% for NiTi SMAs. If the temperature is raised above the austenite finish temperature (A f ), the martensite converts back to austenite (Fig. 1), 7 and the SMA returns to its initial predetermined state, exhibiting the so-called one-way memory effect.

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External heating of stents by radio waves

Cited by 19 publications

References 21 publications

Employing high-frequency alternating magnetic fields for the non-invasive treatment of prosthetic joint infections

Employing high-frequency alternating magnetic fields for the non-invasive treatment of prosthetic joint infections

A Novel Shape Memory Plate Osteosynthesis for Noninvasive Modulation of Fixation Stiffness in a Rabbit Tibia Osteotomy Model

Electromagnetic induction heating of an orthopaedic nickel–titanium shape memory device

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