title: Transcutaneous electromagnetic induction heating of an intramedullary nickel-titanium shape memory implant.
abstract: OBJECTIVE
  Inadequate mechanical stimuli are a major cause for nonunions following surgery for femoral and tibial shaft fractures. Adapting fixation rigidity during the course of fracture healing requires additional surgery. Nickel-titanium (NiTi) implants can change shape and rigidity by employing a temperature-dependent shape-memory effect. As a first step in the development of advanced intramedullary (IM) NiTi devices for fracture healing, this study aimed to test the feasibility and safety of transcutaneous electromagnetic induction heating of an IM NiTi implant in a rat model.
  
  
  METHODS
  In 51 rats, NiTi implants were introduced into the left distal femur. Forty-four animals were transferred to an induction coil, and the implant was electromagnetically heated to temperatures between 40° and 60 °C Blood samples were drawn before and four hours after the procedure. Interleukin (IL)-1, IL-4, IL-10, tumour necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ) were measured. Animals were sacrificed at three weeks. Histological specimens from the hind leg and liver were retrieved and examined for inflammatory changes, necrosis or corrosion pits.
  
  
  RESULTS
  All animals successfully underwent the surgical procedure. Following transcutaneous induction heating, target temperature was confirmed in 37/44 rats. Postoperative controls showed no signs of undue limitations. Neither cytokine measurements nor histological specimens showed any significant differences between groups. There were no corrosion pits or necrosis.
  
  
  CONCLUSIONS
  We conclude that electromagnetic induction heating of IM NiTi implants is feasible and safe in a rat femur model. These findings reflect a further step in the development of novel concepts for IM fracture fixation that might lead to better fracture healing, less patient discomfort and less need for surgical interventions.
authors.affiliation: Trauma Department, Hannover Medical School (MHH), Hannover, Germany, mueller.christian@mh-hannover.de.
authors.forename: Christian W
authors.initials: CW
authors.lastname: Müller
authors.forename: Tarek
authors.initials: T
authors.lastname: ElKashef
authors.forename: Ronny
authors.initials: R
authors.lastname: Pfeifer
authors.forename: Sebastian
authors.initials: S
authors.lastname: Decker
authors.forename: Claudia
authors.initials: C
authors.lastname: Neunaber
authors.forename: Karen
authors.initials: K
authors.lastname: Meier
authors.forename: Michael
authors.initials: M
authors.lastname: Fehr
authors.forename: Volker
authors.initials: V
authors.lastname: Wesling
authors.forename: Thomas
authors.initials: T
authors.lastname: Gösling
authors.forename: Christof
authors.initials: C
authors.lastname: Hurschler
authors.forename: Christian
authors.initials: C
authors.lastname: Krettek
mesh_terms: D000818:Animals; D016207:Cytokines / Q000097:blood; D055590:Electromagnetic Phenomena; D005269:Femur / Q000601:surgery*; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation / Q000379:methods*; D017102:Fracture Healing / Q000502:physiology*; D006361:Heating / Q000009:adverse effects / Q000379:methods*; D006614:Hindlimb; D006801:Humans; D008099:Liver / Q000473:pathology; D008297:Male; D009532:Nickel / Q000627:therapeutic use*; D019736:Prostheses and Implants; D051381:Rats; D017207:Rats, Sprague-Dawley; D013978:Tibial Fractures; D014025:Titanium / Q000627:therapeutic use*
chemical_list: D016207:Cytokines; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium