title: A new model of implant-related osteomyelitis in the metaphysis of rat tibiae.
abstract: BACKGROUND
  Animal models serve as an important tool to understand peri-implant infection. Most of the models use high bacterial loads (>10(4) colony forming units, CFU) to provide high infection rates. Therefore these animals evolve rather similarly, making comparison between groups and statistical analysis possible. On the other hand, to mimic clinical constellation of surgery-related infections the use of low amounts of bacteria would be more advantageous.
  
  
  METHODS
  We developed a metaphyseal rat model of peri-implant bone infection with low amount of bacterial loads (10(2) and 10(3) CFU of Staphylococcus aureus) and investigated osseointegration of the implants coated with hydroxyapatite (HA) and low-dosed HA-silver (HA-Ag). Non-infected implants served as controls. After 6 weeks rats were sacrificed and implants evaluated for osseointegration and infection.
  
  
  RESULTS
  Infection of implanted devices was reliably induced, independently whether 10(2) or 10(3) CFU of S. aureus were inoculated and HA or HA-Ag coated implants were used. No systemic infection was present in any of the animals at the time of sacrifice, and no animal developed acute infection requiring premature sacrifice. All CFU counts of the implant and the bone at sacrifice were significantly higher than the inoculated load (p < .05). All sterilely inserted implants showed excellent osseointegration and no infection.
  
  
  CONCLUSIONS
  Our present study of a rat tibia model reliably induced osteomyelitis in the metaphysis with low-doses of bacteria. The addition of low-dosed Ag to the implant coating was not able to reduce the infection rates. The results demonstrate that it is possible to develop a model of implant-related osteomyelitis in rats with low amounts of bacteria to better mimic clinical constellations. No other promoters of infection besides insertion of the screw implant were used in this model.
authors.affiliation: Clinic of Orthopedics and Sports Orthopedics, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany. norbert.harrasser@outlook.de.
authors.forename: Norbert
authors.initials: N
authors.lastname: Harrasser
authors.affiliation: Clinic of Orthopedics and Sports Orthopedics, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Gorkotte
authors.affiliation: Clinic of Orthopedics and Sports Orthopedics, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Obermeier
authors.affiliation: Institute for Medical Microbiology and Immunology, Technical University of Munich, Trogerstr. 30, 81675, Munich, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Feihl
authors.affiliation: Institute of Pathology, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Straub
authors.affiliation: Institute of Pathology, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Slotta-Huspenina
authors.affiliation: Clinic of Orthopedics and Sports Orthopedics, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.
authors.forename: Ruediger
authors.initials: R
authors.lastname: von Eisenhart-Rothe
authors.affiliation: Atesos medical AG, Schachenallee 29, CH-5000, Aarau, Switzerland.
authors.forename: Walter
authors.initials: W
authors.lastname: Moser
authors.affiliation: Medicoat AG, Almuesenacherstrasse 2a, CH-5506, Maegenwil, Switzerland.
authors.forename: Philipp
authors.initials: P
authors.lastname: Gruner
authors.affiliation: University of Applied Sciences and Arts Northwestern Switzerland (FHNW), School of Life Sciences, CH-4132, Muttenz, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: de Wild
authors.affiliation: Clinic of Orthopedics and Sports Orthopedics, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.|ATOS Clinic, Effnerstr.38, 81925, Munich, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Gollwitzer
authors.affiliation: Clinic of Orthopedics and Sports Orthopedics, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Burgkart
mesh_terms: D000818:Animals; D001863:Bone Screws / Q000009:adverse effects / Q000382:microbiology*; D004195:Disease Models, Animal; D008297:Male; D010019:Osteomyelitis / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D013203:Staphylococcal Infections / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology; D013211:Staphylococcus aureus
keywords: Implant-associated infections; Metaphysis; Rat; Screw; Staphylococcus aureus