Sterilization is most often defined as the process of making a host object free of surface bacteria or related microorganisms. The overall technique of sterilization can be broken down into 2 categories:

  • Physical (irradiation, heat or steam) and
  • Chemical (Ethylene oxide, ozone, glutaraldehyde, or phenols).

Sterilization has increasingly been a topic of discussion from the time orthopedic implants become part of the mainstream. The ultimate goal in avoiding contamination is to sterilize implantation devices without compromising the innate integrity of the tissue. The amount of wear has been found to be directly subject to the sterilization technique, used during the implantation.

Proper sterilization relies on a combination of processes which together form an infection control system. The science of sterilization of implants is currently on the cusp of change. Successful sterilization of biomaterials used in implants and devices is a critical prerequisite for their successful clinical application. The challenge for the biomaterial scientist responsible for defining a terminal sterilization process is an optimization problem.

Material compatibility constraints often drive the choice of sterilization modality. Two terminal sterilization modalities, radiation sterilization, and ethylene oxide sterilization dominate the industrial terminal sterilization market. The most commonly used sterilzation methods are:

  • Steam sterilization
  • EtO sterilization and
  • Radiation sterilization specifically Gamma irradiation

Implants and devices which are categorized as critical should be sterilized properly before their introduction into the patient’s body.



  • It is one of the most commonly used sterilization methods for implantable medical devices.
  • This method use high-temperature steam and pressure to kill micro-organisms. Typical operating temperatures are 121-1410C with a pressure range of 206-368 kPa.
  • The minimum recommended standard for sterilization is exposure to steam at a pressure of approximately 1 bar equivalent to 1210C for 15 minutes.
  • The steam method is convenient, fast, and widely available.
  • It is inexpensive and can quickly sterilize porous materials and accessible surfaces and spaces.
  • Gravity displacement autoclave and high-speed pre-vacuum sterilizer are the 2 fundamental types of steam sterilizers.
  • Flash(steam) sterilization is a modification of conventional steam sterilization.
  • Pre-vacuum cycle and single wrap cycle and some of the types of flash sterilization.
  • Efficacy
  • Process simplicity
  • Speed.
  • Reliability.
  • Nontoxicity.
  • Rapidity.
  • Ideal nature for metal instruments.
  • Ability to penetrate fabrics.
  • Portability. Tabletop sterilizers are available.
  • Mechanical properties like osteoconductivity, and stiffness are retained by bone grafts even after steam sterilization.
  • Temperature-sensitive
  • Steam may hydrolyze or degrade certain plastics.
  • Autoclaving increased cytotoxicity of orthodontic elastics in chain form.
  • Lubricants associated with dental hand-pieces get corroded and combusted.
  • In laryngoscopes transmission of light is reduced.
  • Laboratory media and water.
  • Pharmaceutical products.
  • Non-porous articles.
  • Regulated medical wastes.
  • Metallic surgical instruments.
  • Stainless steel sutures.
  • Intravenous solutions.


  • Here sterility is obtained by exposure of the materials at extreme temperature (>1400C).
  • B.subtilis must be used to monitor the dry heat sterilization process since they are more resistant to dry heat than others.
  • Temperature-time relationships for hot air sterilizers are
    • 1700C for 60 min
    • 1600C for 120 min
    • 1500C for 150 min
  • The two types of sterilizers used here are
    • FORCED AIR TYPE STERILIZERS – Employs a motor driven blower
  • Demerits of static type over forced type are:
    • Low rate of heating
    • High time consumption
  • Surface characteristics like surface topography and energy can change due to exposure to dry heat.
  • Oxidation of cellular constituents during dry heat sterilization is considered the primary lethal process.


  • Ethylene oxide gas is toxic, carcinogenic, and very explosive.
  • EtO sterilization cycles must be designed to avoid conditions or parameters that may be explosive.
  • EtO has been the primary means of sterilization for medical devices, as it causes an internal chemical reaction that leads to microorganism destruction.
  • Materials sterilized with EtO need to be aerated in a well-ventilated room or placed in an aerator.
  • EtO is a very effective sterilization method that is compatible with a wide range of biomaterials.
  • Low-temperature sterilization process.
  • Efficacy even at low temperatures.
  • High penetration ability.
  • High microbicidal activity.
  • Compatibility with a wide range of materials.
  • EtO-CO2 gas mixture, an eco-friendly sterilant.
  • Diluents used generally don’t affect the principles of operation and validation of an EO cycle.
  • 12 to 16 hours is required for sterilization and aeration.
  • Due to environmental concerns, EtO sterilizations are not allowed in some countries. eg(Canada).
  • Explosions can be horrific in magnitude, and extreme care must be taken.
  • Costly explosion-proof equipment
  • Complex process.
  • Formation of toxic residues.
  • Neurosurgery devices
  • Absorbable bone repair devices
  • Ligament, and tendon repair devices.
  • Intraocular lens
  • Heart valves
  • Vascular grafts
  • Endoscopes


  • Sterility of implants is achieved by their exposure to ionizing radiation which is often a high-energy electron beam.
  • Radiation sterilization doses are lethal.
  • Significant shielding, robust interlocks, and the utmost care are required in radiation processing facilities.
  • Ionizing radiation penetrates both the implants and the contaminating micro-organisms.
  • Ionizing radiation is more efficient than UV radiation
  • Efficacy
  • Rapidity
  • Simplicity
  • High penetrating power
  • Electron beam has easy storage
  • Measurability and controllability
  • Suitable for large-scale sterilization
  • Attenuation diminishes sterilization power
  • Thick and densely packed materials can’t be sterilized in an electron beam
  • Cross-linking may result in undesirable effects of radiation sterilization
  • Continue decay of an isotope
  • Radiation may decrease the lifetime of implants of long-term usage
  • Efficient combination of sterilants for glucose biosensors
  • Orthodontic elastic chain
  • Titanium implants using UV rays
  • In-line sterilization of thin products
  • Surgical sutures and drapes
  • Metallic bone implants
  • Knee and hip protheses
  • Pharmaceutical containers
  • Neurosurgery devices

Click to read about atherosclerosis

Click to read about tech blogs