Proper sterilization of surgical instruments is one of the most critical infection control processes in healthcare. Failure to adequately sterilize surgical instruments can result in surgical site infections, patient harm, and serious regulatory consequences. This guide provides an overview of the main sterilization methods used for reusable and single-use surgical instruments.
Understanding Sterility Assurance
Before reviewing specific methods, it's important to understand Sterility Assurance Level (SAL). SAL is expressed as the probability of a viable microorganism remaining on a sterilized product. The accepted SAL for surgical instruments is 10⁻⁶ — meaning there is a 1 in 1,000,000 probability that a viable organism is present after sterilization. All validated sterilization processes must achieve this SAL.
Steam Sterilization (Autoclave)
Steam sterilization (autoclaving) is the most widely used and cost-effective method for sterilizing reusable stainless steel surgical instruments.
How it works: High-pressure saturated steam at 121–134°C destroys microorganisms through protein denaturation and enzyme inactivation.
Key parameters:
- ›Pre-vacuum cycle: 134°C for 3 minutes (common in UK/EU)
- ›Gravity cycle: 121°C for 15–30 minutes
- ›Pressure: 2–3 bar
Advantages:
- ›Effective against all microorganisms including prions (with validated cycles)
- ›Low cost per cycle
- ›No toxic residuals
- ›Rapid turnaround
- ›Suitable for all stainless steel instruments
Limitations:
- ›Not suitable for heat-sensitive materials (some plastics, electronics)
- ›Instruments must be thoroughly cleaned and dried after use
- ›Packaging must be breathable (pouches, wraps) to allow steam penetration
All Stepwin Industries stainless steel instruments are rated for repeated steam autoclave sterilization at 134°C, 3 bar.
Ethylene Oxide (ETO) Sterilization
ETO is a gas used to sterilize heat-sensitive medical devices and instruments that cannot withstand steam sterilization.
How it works: ETO alkylates cellular components (DNA, proteins, enzymes), preventing cellular reproduction.
Key parameters:
- ›Temperature: 37–63°C
- ›Relative humidity: 40–80%
- ›ETO concentration: 600–800 mg/L
- ›Cycle time: 2–16 hours + mandatory aeration period
Advantages:
- ›Effective at low temperatures
- ›Suitable for heat-sensitive instruments and single-use items
- ›Good material compatibility
Limitations:
- ›Long cycle times (including mandatory aeration)
- ›Toxic gas — requires specialized equipment and safety controls
- ›ETO residuals on treated items (aeration required)
- ›Increasing regulatory restrictions on ETO use
Hydrogen Peroxide Plasma Sterilization
Low-temperature hydrogen peroxide plasma (e.g., Sterrad®) is an increasingly popular alternative to ETO for heat-sensitive items.
How it works: Hydrogen peroxide vapour is diffused into a low-pressure chamber, then activated by radio frequency energy to form a plasma, which destroys microorganisms.
Key parameters:
- ›Temperature: 45–55°C
- ›Cycle time: 28–75 minutes
- ›No toxic residuals
Advantages:
- ›Low temperature — suitable for heat-sensitive items
- ›Short cycle time vs. ETO
- ›No toxic residuals — instruments ready to use immediately
- ›Environmentally friendly
Limitations:
- ›Cannot sterilize items with long narrow lumens (≥1mm diameter, >31cm length)
- ›More expensive per cycle than autoclave
- ›Limited to non-cellulose packaging materials
Gamma Irradiation Sterilization
Gamma irradiation is used for industrial sterilization of large quantities of single-use surgical instruments and procedure packs.
How it works: High-energy gamma rays (from Co-60 source) destroy microorganisms through direct DNA damage and ionization of cellular components.
Key parameters:
- ›Minimum dose: 25 kGy (for SAL 10⁻⁶)
- ›Validated dose: Established per product using bioburden analysis
- ›Temperature: Ambient (no heating)
Advantages:
- ›Effective at room temperature
- ›Deep penetration through packaging
- ›No residuals
- ›Validated shelf life (typically 5 years for single-use instruments)
- ›Suitable for large production quantities
Limitations:
- ›Requires a specialist gamma irradiation facility
- ›Not available for on-site use in hospitals
- ›Some material degradation possible with repeated doses
All Stepwin Industries single-use disposable instruments are gamma sterilized to a minimum dose of 25 kGy, achieving SAL 10⁻⁶.
Choosing the Right Sterilization Method
The choice of sterilization method depends on:
- ›Instrument materials (heat tolerance, material compatibility)
- ›Clinical application (reusable vs. single-use)
- ›Available equipment and facility resources
- ›Regulatory requirements in your country/region
- ›Volume and throughput requirements
For guidance on sterilization of specific Stepwin Industries instruments, please refer to the Instructions for Use (IFU) provided with each product, or contact our technical support team.