Steam sterilization validation of
Smith & Nephew orthopaedic
instrument sets in reusable
rigid container systems
This white paper summarizes the testing that was carried out on Smith & Nephew orthopaedic instrument
sets in Aesculap and Case Medical perforated bottom rigid container systems. A rigid container is a reusable
case system that is used as an alternative to the traditional woven or nonwoven wrapping materials that are
used to sterilize medical devices and containment devices.
Sterilization validation was carried out using the ‘overkill’ approach. Biological indicators, temperature profiles
and dryness testing were used to show that Smith & Nephew instrument sets could be adequately sterilized
in the rigid container systems by a typical hospital steam sterilization cycle.
Biological Indicator (BI)
A measured number of microorganisms in a test system (i.e., a strip)
that provides a defined resistance to the specified sterilization process.
Small containment device or flip-up case that is used to contain and
organize small medical devices, i.e., plates, screws.
Containment devices are any reusable container (i.e. instrument case,
caddy or tray) that is designed for use in healthcare facilities for the
purpose of containing reusable medical devices for sterilization. In this
white paper the containment devices inside the instrument sets are
caddies and instrument trays.
DataTrace Temperature Logger
A programmable temperature monitoring device that can collect
temperature data at specified intervals during a sterilization cycle.
Time or dose required to achieve inactivation of 90% of a population
of a test microorganism under stated conditions.
Time required to dry steam sterilized items inside the sterilizer.
Period for which the process parameters are maintained within their
A containment device that has a bottom but no lid and that is used to
organize reusable medical devices for sterilization. The instrument tray
is designed to go inside of a larger containment device as a part of an
A steam sterilization test method in which steam resistant BIs are
exposed to a half exposure cycle to demonstrate the inactivation of at
least 12 logarithms of bacterial spores with a D value of one (1) minute
at a temperature of 121ºC and a z value of approximately 10ºC for a
Pre-vacuum Steam Sterilization
Also known as dynamic air removal steam sterilization. One of two
types of sterilization cycles in which air is removed from the chamber
and the load by means of a series of pressure and vacuum excursions
Sterilizer that uses saturated steam under pressure as the
A process used to render a product free of microorganisms.
Sterility Assurance Level (SAL)
Probability of a single viable microorganism occurring on product
Documented procedure for obtaining, recording and interpreting the
results required to establish that a process will consistently yield
product complying with predetermined specifications.
Aesculap SterilContainer™ System Containers JN440, JN442, JN444, JN446 and Case Medical SteriTite® SC06FG
Disposable sterile filter paper
DataTrace temperature monitoring loggers and computer interface system
AMSCO Century Sterilizer, Model #SV 120
Ethox Geobacillus stearothermophilus paper biological indicators (BIs) – population -106, D value -2 minutes
SCDM (Soybean Casein Digest Media)
Incubator capable of 55-60ºC
ID of Smith & Nephew instrument set representatives used for testing
Three Smith & Nephew instrument sets were determined to be worst case and to represent all Smith & Nephew
case families. The criteria used to determine the worst case instrument sets were the materials of construction,
types and numbers of internal containment devices, density, flow area/mass ratio (which is based on the
number of flow holes in the case) and weight. Table 1 identifies the representative instrument sets that were
used for testing.
Instrument set representative Challenging case features
PROFIX™ Revision System
Represents upper end of weight for cases with plastic trays; contains
three plastic trays: a top, middle and bottom tray.
TC-100™ Small Fragment Case
Represents worst case for cases that contain multiple caddies;
contains four metal and plastic caddies.
GENESIS™ II Revision Tibial
Represents upper end of weight for cases with metal trays, contains
two metal trays: an upper and lower tray.
Aesculap rigid containers used for testing
Two rigid container systems have been validated by Smith & Nephew for use with Smith & Nephew instrument
sets: 1) Aesculap SterilContainer with perforated bottom and 2) Case Medical SteriTite™ rigid container with
perforated bottom. These rigid containers are made of aluminum and have filter retention plates on the lid and
case bottom for placement of disposable filters. Figure 1 shows the design of the rigid cases that were tested.
Figure 1: Rigid containers
Case Medical SteriTite™
Placement of Smith & Nephew representative instrument sets in rigid container
For each Smith & Nephew representative set, all of the internal containment devices (CDs) were removed from
the outer case of the set and placed inside the rigid container(s) in a manner that met the acceptable weight
limit of 25 lbs. In most cases, the instrument CDs were stacked inside the rigid container(s).
The weight of each representative instrument set in each of the Aesculap and Case medical rigid containers
was measured to determine if the acceptable 25 lb weight limit was met. All of the instrument sets with rigid
containers were within the 25 lb weight limit. The upper and lower trays of the GENESIS™ II Revision Tibial Set
had to be processed in separate rigid containers in order to meet the 25 lb weight limit.
BI and temperature monitor placement
BIs and DataTrace temperature loggers were placed at locations inside the instrument set containment devices
that were determined to be the most difficult to sterilize. A DataTrace temperature logger was also placed at
the center of the case and at the drain of the autoclave.
Overkill testing and temperature monitoring
Sterilization validation testing was carried out using the ‘overkill’ approach and temperature monitoring to
demonstrate a Sterility Assurance Level (SAL) of 10-6. For overkill testing, steam-resistant BIs with a population
of 106 spores and a minimum D value of one (1) minute must be sterile following a half exposure cycle. For
temperature monitoring, the temperature inside the cases must reach the exposure temperature during the
The autoclave was fully loaded for each test cycle with one case on the top shelf and one on the bottom shelf.
The half exposure cycle parameters were: Prevacuum Steam Sterilization Cycle, Exposure Temperature - 132ºC,
Exposure Time - 1.5 minutes. After the cycle, the BIs and DataTrace temperature loggers were removed. The
BIs were aseptically transferred to 10ml of Soybean Casein Digest Media and incubated for seven (7) days at
55-60ºC. Growth of the indicator organism is indicative of a non-sterile result. The temperature data from the
DataTrace loggers was downloaded using the DataTrace computer interface system. For each representative
set pre-vacuum half exposure steam sterilization cycle tests were carried out.
The dryness of Smith & Nephew instrument sets following sterilization is included in the validation process
because dryness following sterilization is critical in maintaining the sterility of the instruments. For this testing,
a full cycle is run at a specified dry time. The case and its contents are then inspected for the presence
For testing of each representative instrument set inside the rigid container, the CDs in the instrument set were
removed and placed in the rigid container. The autoclave was fully loaded with one case on the top shelf and
one on the bottom shelf. A full pre-vacuum steam sterilization cycle with a 30-minute dry time was conducted.
The full cycle parameters were: pre-vacuum, 4 pulses, 132°C exposure temperature, 3-minute exposure time,
30-minute dry time.
After the cycle, the rigid containers were removed from the chamber and placed on a wire rack that was
covered with a sheet of sterilization wrap. The set was allowed to cool for 30 minutes at room temperature.
The rigid containers were then inspected for the presence of moisture by removing the lid and inspecting
the rigid container base and lid, instrument set CDs and instruments.
Results and analysis
Overkill testing/BI results
The BI results from overkill half cycle exposure testing for the Aesculap Sterilcontainer (Aes) and the Case
Medical Steritite® (C Med) rigid containers are given in Table 2.
Sterility Results (# of positive BIs/total # of BIs)
Instrument Set Representative
TC-100™ Small Fragment
PROFIX™ Tibial Revision
GENESIS™ II Tibial Upper Tray
GENESIS II Tibial Lower Tray
For all Smith & Nephew instrument sets, there were no positive BIs in any of the three overkill half exposure
test cycles for both rigid container systems.
The temperature monitoring results showed that the set exposure temperature of 132°C was achieved during
the exposure phase for all three validation test cycles. All of the temperature profiles for both rigid container
systems followed the same temperature profile pattern. A graph of one of the temperature profiles from the
rigid container studies is shown in Figure 2.
Figure 2: Rigid Container Temperature Profile
TC 100™ Small Frag/Aesculap Rigid Container Study
Prevacuum 132oC 1.5 min Half Cycle
Temperature ( oC)
Bottom of Center
900 1050 1200 1350 1500 1650 1800 1950 2100
Dryness testing results
Moisture was not observed in the rigid containers, instruments or CDs following the pre-vacuum steam
sterilization cycles for all rigid container systems.
The results showed that Smith & Nephew instrument sets processed in Aesculap Sterilcontainer™ systems
JN440, JN442, JN444, JN446 and Case Medical SteriTite® SC06FG rigid containers can be sterilized to a 10-6
sterility assurance level (SAL) in a Dynamic Air Removal (pre-vacuum) Steam Sterilization Cycle: Exposure
temperature: 132°C (270°F), Exposure time: 4 minutes OR, Exposure temperature: 135ºC (275ºF), Exposure
time: 3 minutes.
Smith & Nephew does not recommend the use of Gravity Displacement steam cycles for sterilization of
Smith & Nephew instrument sets in Aesculap rigid container systems.
1. AAMI TIR 12:2004, “Designing, Testing, and Labeling Reusable Medical Devices for Reprocessing in Health Care Facilities: a Guide for Device Manufacturers”,
2. ANSI/AAMI/ISO 14161:2000, Sterilization of healthcare products - Biological indicators - Guidance for the selection, use, and interpretation of results.
3. ANSI/AAMI ST77:2006, “Containment devices for reusable medical device sterilization.”
4. ANSI/AAMI ST79:2006, “Comprehensive guide to steam sterilization and sterility assurance in health care facilities.”
5. Aesculap Instructions for Use for STERILCONTAINER SYSTEMTM, 405-03-1007, AIC-5000238.
6. “Recommendations for Decontamination and Sterilization of Smith and Nephew Inc. Orthopaedic Medical Devices”, Smith & Nephew Item # 7198-0826, Rev 8/08.
7. Sterilization of healthcare products- Biological indicators- Guidance for the selection, use, and interpretation of results.
8. Case Medical SteriTite® Instructions for Use, 2009.
Smith & Nephew, Inc.
7135 Goodlett Farms Parkway
Cordova, TN 38016
Orders and Inquiries: 1-800-238-7538
™Trademark of Smith & Nephew. Reg. US Pat. & TM Off. All Trademarks acknowledged.
©2013 Smith & Nephew, Inc.
00418 v1 08/13