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Influence of metal implants on infection. An experimental study in rabbits
J Cordero1, L Munuera, M D Folgueira
1La Paz Hospital, Madrid, Spain.
Abstract:
We implanted cylinders of cobalt-chrome or titanium, with smooth or porous surfaces, into rabbit bones which had been inoculated with suspensions of Staphylococcus aureus in various doses. The bacterial concentration required to produce infection of porous-coated titanium implants was 2.5 times smaller than that necessary to infect implants with polished surfaces. Porous-coated cobalt-chromium implants required bacterial concentrations that were 40 times smaller than those needed to infect implants with polished surfaces, and 15 times smaller than those required to infect porous-coated titanium implants. The other advantages and disadvantages of the various implants, such as improved osseointegration, larger ion-release surfaces, surface wear and relative stiffness, must be weighed against the higher infection rates in the porous-coated implants, and particularly in the cobalt-chromium implants.
Insights
Porous-coated implants, especially cobalt-chromium, are more prone to Staphylococcus aureus infection than smooth implants. This increased infection risk must be considered alongside potential benefits like osseointegration.
Area of Science:
- Biomaterials Science
- Infectious Disease Research
- Orthopedic Surgery
Background:
- Orthopedic implants are susceptible to bacterial colonization, leading to infections.
- Surface properties of implants, such as porosity, can influence bacterial adhesion and infection risk.
- Cobalt-chromium and titanium are common biomaterials used in orthopedic implants.
Purpose of the Study:
- To investigate the susceptibility of different orthopedic implant materials and surface topographies to Staphylococcus aureus infection.
- To compare the infection thresholds for smooth versus porous-coated cobalt-chromium and titanium implants.
Main Methods:
- Cylindrical implants of cobalt-chrome and titanium with smooth or porous surfaces were implanted into rabbit bones.
- Bones were inoculated with varying doses of Staphylococcus aureus.
- Infection rates were assessed based on bacterial concentration and implant type.
Main Results:
- Porous-coated titanium implants required 2.5 times lower bacterial concentrations to cause infection compared to polished surfaces.
- Porous-coated cobalt-chromium implants required 40 times lower bacterial concentrations than polished surfaces and 15 times lower than porous-coated titanium.
- Porous-coated implants, particularly cobalt-chromium, demonstrated significantly higher susceptibility to Staphylococcus aureus infection.
Conclusions:
- The porous surface topography of orthopedic implants significantly increases susceptibility to Staphylococcus aureus infection.
- Cobalt-chromium implants with porous surfaces exhibit the highest risk of infection.
- Clinical decisions regarding implant selection must balance the benefits of porous surfaces (e.g., osseointegration) against their increased risk of infection.