Suture Sterilisation and Packaging

Sterilisation is a validated process that reduces the probability of a viable micro-organism surviving on a device to a defined level. Packaging is what preserves that state until the pack is opened. For a surgical suture, both are part of the device rather than an afterthought to it.

By Dolphin Sutures Reviewed by Dolphin Sutures Last reviewed August 5, 2026

Why it matters

A suture is not sterile because it was made cleanly. It is sterile because a validated process was applied to it and a barrier has held ever since. Which process was used is not an administrative detail either: it constrains what the polymer can be, and it is one of the reasons absorbable and non-absorbable sutures are not manufactured the same way.

Sterility is a property of the pack, not the strand

Sterility is expressed as a sterility assurance level, or SAL. The conventional requirement for a terminally sterilised surgical device is an SAL of 10⁻⁶: the probability that any given unit carries a surviving viable organism is not more than one in a million.

It is worth reading that carefully, because it is a probabilistic claim about a validated process, not a promise that every strand has been individually inspected. And it applies to the device as packaged. The moment the sterile barrier is breached — opened, torn, punctured or wetted — the claim no longer holds, whatever the label says.

Ethylene oxide

Ethylene oxide is a gas that inactivates micro-organisms by alkylation. Its useful properties for suture manufacture are that it works at low temperature and that it penetrates gas-permeable packaging, so the device can be sterilised after it is sealed in its pack.

Low temperature is the decisive advantage. Suture polymers — and absorbable polyesters in particular — are sensitive to heat and to radiation, and a process that avoids both leaves the material closer to how it was made. The cost is that residual gas and its by-products must be driven off by a controlled aeration step, and permitted residual limits are themselves regulated. The process is governed by ISO 11135; residual limits fall under ISO 10993-7.

Gamma irradiation

Gamma irradiation uses ionising radiation, conventionally from a cobalt-60 source. It penetrates far more aggressively than gas — whole sealed cartons can be treated — and it leaves no chemical residue to aerate. For many non-absorbable materials it is an efficient and entirely appropriate choice. It is governed by ISO 11137.

The difficulty is what ionising radiation does to a polymer. Depositing that much energy in a long-chain molecule can cause chain scission, cutting the chains shorter. For an absorbable polyester whose entire clinical behaviour — how long it holds, how predictably it is absorbed — depends on its molecular weight and a controlled hydrolysis profile, shortening the chains is not a side issue. It is why absorbable synthetic sutures are commonly sterilised with ethylene oxide rather than by irradiation.

The sterile barrier system

The packaging is a system with named parts, and it is validated as such under ISO 11607. The primary pack is the sterile barrier: it is what maintains sterility, and it is the layer whose integrity matters. Inside it, a folder or tray holds the strand so that it is presented without kinking and the needle is not displaced.

For absorbable sutures the barrier does a second job. Absorption is driven by hydrolysis, and hydrolysis begins with water; a foil laminate that excludes moisture is therefore protecting the device’s performance and not only its sterility. The pack is functional packaging, not decoration.

What the expiry date means

The date printed on the pack is the limit of what the manufacturer has evidence for. It is established from ageing studies — real-time, and accelerated ageing as a predictive tool — that show both the device and its sterile barrier still meet specification at that point.

So it is neither a guess nor a cliff edge on which something abruptly fails. It is the boundary of a validated claim, which is precisely why expired stock is not used: past that date the manufacturer is no longer asserting anything, and a hospital cannot substitute its own judgement for evidence it does not have.

Single use, and why re-sterilising is not an option

Sutures are labelled single use. Reprocessing a device that was validated for one sterilisation cycle puts it outside everything that was demonstrated about it: the polymer may have been altered, the needle’s attachment and point are not re-inspected, and no assurance of sterility applies to the second cycle because none was ever established.

The same logic covers a damaged pack. A pouch that has been crushed, torn, punctured or soaked is no longer a sterile barrier, and its contents are handled as unsterile regardless of the printed date.

Key terminology

Sterility assurance level (SAL): The probability that a viable micro-organism is present on a unit after sterilisation. Conventionally 10⁻⁶ for terminally sterilised surgical devices.
Terminal sterilisation: Sterilising the device inside its final packaging, so it is never handled unprotected afterwards.
Ethylene oxide (EO): A sterilising gas that acts by alkylation at low temperature, penetrating gas-permeable packaging. Requires an aeration step.
Gamma irradiation: Sterilisation by ionising radiation, conventionally from a cobalt-60 source. Leaves no residue but deposits energy in the polymer.
Chain scission: The cutting of long polymer chains into shorter ones, which lowers molecular weight and can alter how a material behaves.
Sterile barrier system: The packaging layer that maintains sterility — the primary pack. Validated under ISO 11607.
Aeration: The controlled post-sterilisation step in which residual ethylene oxide and its by-products are driven off to within permitted limits.
Accelerated ageing: Storing product at elevated temperature to predict shelf life faster than real time, used alongside real-time ageing to support an expiry date.
Lot or batch number: The traceability code printed on the pack that ties the device back to its manufacturing and sterilisation records.

Technical characteristics

Typical SAL: 10⁻⁶
Common method — absorbable synthetics: Ethylene oxide
Common method — many non-absorbables: Ethylene oxide or gamma irradiation
EO process standard: ISO 11135
EO residual limits: ISO 10993-7
Radiation process standard: ISO 11137
Packaging standard: ISO 11607
Primary barrier: Sealed pouch, commonly a foil laminate where moisture must be excluded
Reuse: Single use; re-sterilisation is not validated
Traceability: Lot or batch number printed on the pack

How it compares

Ethylene oxide and gamma irradiation compared on the attributes that decide which is appropriate for a given suture material.
Attribute	Ethylene oxide	Gamma irradiation
Agent	Ethylene oxide gas, acting by alkylation	Ionising radiation, conventionally cobalt-60
Temperature	Low	Ambient
Penetration	Through gas-permeable packaging	Through sealed cartons and pallets
Residuals	Requires a validated aeration step; limits regulated	None
Effect on polymers	Chemical; generally gentler on absorbable polyesters	Can cause chain scission, lowering molecular weight
Use with absorbable synthetics	Common	Generally avoided
Governing standard	ISO 11135	ISO 11137

What clinicians weigh when selecting

Material compatibility

The polymer decides the process, not the other way round. An absorbable polyester whose behaviour depends on molecular weight is not a candidate for a process that shortens chains.

Residuals and aeration

A gas process introduces something that must then be removed to a regulated limit, which adds a validated step and time to the cycle.

Packaging must suit the method

Ethylene oxide needs a gas-permeable path into the pack; irradiation does not. The pack and the process are validated as one system.

Validation is per product

A sterilisation process is validated for a defined product, load and configuration. It does not transfer to a different device by analogy.

What the label tells you

Method, expiry date, lot number and single-use status are all on the pack. Reading a suture label covers those symbols in detail.

Frequently asked questions

Are surgical sutures sterilised with ethylene oxide or gamma radiation?

Both methods are used across the industry, but not interchangeably. Absorbable synthetic sutures are commonly sterilised with ethylene oxide because irradiation can shorten polymer chains and alter the absorption profile. Gamma irradiation is used for many non-absorbable materials, where that concern does not apply. The method is stated on the pack.

Why are absorbable sutures usually not gamma sterilised?

Because the clinical behaviour of an absorbable polyester depends on its molecular weight and a controlled hydrolysis profile. Ionising radiation can cause chain scission, cutting polymer chains shorter, which is a change to the very property the device is engineered around.

Can a suture pack be re-sterilised?

No. Sutures are labelled single use, and the sterilisation process was validated for one cycle on that product in that packaging. Reprocessing falls outside everything that was demonstrated about the device, and no sterility assurance applies to a second cycle.

What does the expiry date on a suture pack actually mean?

It is the limit of the manufacturer’s validated claim, established from real-time and accelerated ageing studies showing that both the device and its sterile barrier still meet specification at that date. Beyond it the manufacturer asserts nothing, which is why expired stock is not used.

What if the pack is damaged, opened or wet?

Treat the contents as unsterile. Sterility is a property of the device inside an intact sterile barrier; once that barrier is breached the printed expiry date is irrelevant.

What does SAL 10⁻⁶ mean?

Sterility assurance level: the probability that a viable micro-organism survives on a given unit is not more than one in a million. It describes the assurance a validated process provides, rather than claiming that every individual unit has been tested.

The product Sterile Surgical Sutures Our suture range is supplied terminally sterilised in a sealed sterile barrier, with the method, lot number and expiry stated on every pack. See the range → Quality Quality & Compliance How the manufacturing, sterilisation and quality systems behind the range are certified and controlled. Read more →

Instructions for use

This article describes sterilisation and packaging in general terms. The sterilisation method, expiry date, lot number and single-use status that apply to a particular device are stated on its pack and in its instructions for use, which is the controlled document and the only correct source for them.

Medical & regulatory notice

This article is general reference information for healthcare professionals about how a class of device works. It is not a substitute for the instructions for use supplied with any product, it is not clinical guidance, and it does not describe the regulatory status of any particular device in any particular market. Product availability, indications and classification differ between jurisdictions. Clinical decisions about a patient are for the treating clinician.

References

Written by Dolphin Sutures Medical content, reviewed before publication

Reviewed by Dolphin Sutures In-house regulatory and quality review

Last reviewed August 5, 2026 Reviewed on a scheduled cycle