Maintaining the sterility of a medical device is critical to protect patients and prevent the transmission of disease during a surgery. Achieving sterility and maintaining it are two of the biggest challenges in the medical device industry. Packaging plays a critical role in assisting medical device manufacturers to achieving sterility and maintaining sterility. The main function of sterile packaging is to maintain sterility from the production line to the surgery center. Testing and validations are performed on packaging to ensure that it will maintain its integrity of sterilization to the point of use.

History and Background of Sterile Packaging in Medical Devices

In 1993, medical device manufacturers sought after packaging that would maintain sterile product safety and efficacy. This was believed to be prompted after medical device manufacturers started to inquire about CE marks for products. The notified bodies started to ask questions about packaging, and this led to the development of ISO 11607, Packaging for Terminally Sterilized Medical Devices, which was published in 1997. ISO 11607 since has evolved into the main standard for medical device packaging globally. The Association for the Advancement of Medical Instrumentation, AAMI, later developed TIR 22 (Guidance For ANSI/AAMI/ISO 11607, Packaging for Terminally Sterilized Medical Devices) as a guidance document for ISO 11607. Then, ISO TS 16775 was created to serve as the international technical specification for guidance of ISO 11607. In 1996, the FDA released Quality System Regulation which required medical device companies to consider packaging during design control. As additional standards were created, standardized testing evolved to estimate the ability of packaging for medical devices to be compatible to sterilization exposures, to go through distribution cycles, and to maintain integrity over the life span of the device.

Why is Sterile Packaging Important in Medical Devices?

It has been reported that three million people die every year from infections contracted in hospitals while being treated for unrelated ailments. These infections are caused by small microorganisms (bioburdens and pathogens) that may be picked up during any point in the device manufacturing and distribution process. Sterilizing the device and packaging will mitigate the risk of infection. The most common sterilization methods for medical devices are gamma, electron beam (E-beam), ethylene oxide (ETO) and autoclave. Sterile Packaging that is done properly can lower the post-operation infection rate significantly and reduce the number of deaths annually. Sterile Packaging allows a medical device to be enclosed in various packaging materials that allow penetration of the sterilizing agent, maintain sterility of the device after sterilization, be easy to open, and allows for aseptic delivery.

Types of Sterile Packaging in Medical Devices

The main types of sterilization packages in medical devices are trays (metal or plastic) and pouches (paper/plastics).

Thermoformed Trays: Trays can be made of thermoformed plastic or metal. Thermoformed trays are custom to the application. Thermoformed trays provide a cost effective packaging solution that is durable and creates a sterile barrier. Thermoformed trays are sealed with Tyvek® lipstock. Tyvek® is a 100% synthetic material made from high-density spunbound polyethylene fibers. It is lightweight, durable and breathable, yet resistant to water, abrasion, bacterial penetration and aging.

Metal Trays: Metal trays are typically used to store instruments or screws for a medical system. Metal trays are made from aluminum or stainless steel. Metal trays are fully customizable to fit the needs of the products. They may contain polymers inserts for lightweight durable protection of devices. They also allow for multiple devices to be organized, delivered, and sterilized at the same time. Trays are wrapped with flat wrap during sterilization to maintain sterility after the sterilization cycle.

Pouches: Medical device pouches are configured with a combination of plastic, aluminum foil, and/or Tyvek®.

Polyethylene or Polyamide film pouches

Devices that require protection against exposure to light, moisture or oxygen are packaged in Polyethylene or Polyamide film pouches. Polyethylene and Polyamide films offer high moisture and gas barriers. Polyethylene or Polyamide film pouches can not be gas sterilized without using a Tyvek® or medical paper strip inserted in the pouch so that the gas can pass through and sterilize the medical device. Otherwise, Polyethylene or Polyamide film pouches alone will not allow the gas to penatrate the film.

Aluminum Foil Pouches

Devices that are photo sensitive or require high moisture resistance are packaged in Aluminium foil based pouches. Aluminium Foil is combined with Polyamide or Polyethylene based films for providing heat seal, a lint free easy peel, and protection from sharp edges of packed device. Aluminium foil based pouches are sterilized by treating them with radiation.

Tyvek® Pouches

Tyvek® pouches are used for devices that are low-profile and lightweight. Tyvek® sterilization pouches are made from transparent Polyester/Polyethylene copolymer film and uncoated Tyvek® film. Tyvek® membrane is durable, flexible, breathable, tear and puncture resistant, light weight, water resistant and microbial resistant material.

Testing to Ensure Sterility

There are three primary attributes of medical device packaging: integrity, strength, and microbial barrier.

Integrity: To evaluate the integrity of packaging there are two tests that are commonly performed: dye migration and bubble emission. Dye migration a test in which liquid dye is introduced inside the package. The package is rotated until all seals have been exposed to the dye. A channel of dye visible through the seal indicates an open channel in the seal of the package and a breach of integrity. A failure of the dye migration test is a result of a problem with the package sealer. Bubble emission is a whole package integrity test and is done by immersing the package into a tub of fluid and then inflating or introducing air into the package. The packaging fails when bubbles are observed escaping from a single point. Bubble emission failures are often the result of friction caused during shipping, handling, and transportation and processing of the packaging materials. Folds in the packaging material can also be a source of failure, as this fold can become weak and cause leaks. Pointed, sharp, or heavy medical devices can also create pinhole failures caused by friction or impact with packaging.

Strength: The strength of the packaging is determined by how much force is required to open the package. There are three main tests to determine the strength of a package: seal peel, burst, and creep. Seal peel is a test that evaluates the strength of the package and is a tool to help the manufacturer achieve the desired settings for the packaging equipment. Burst testing identifies the pressure at which the weakest seal will burst and the burst pressure for the packaging. The creep test can then be conducted by inflating the sealed package to 80 percent of the burst test benchmark and measuring the length of time or ‘creep’ until package failure. The creep test checks to see whether the packaging will hold at pressure for the time needed.

Microbial Barrier: Microbial barrier tests evaluate the package’s ability to withstand microbial penetration. The test method commonly used is the exposure chamber method. The exposure-chamber method is a quantitative procedure for determining the microbial-barrier properties of porous materials under the conditions specified by the test. Data obtained from this test is useful in assessing the potential of a particular porous material in contributing to the loss of sterility to the contents of the package versus another porous material.

Conclusion

Maintaining the sterility of a medical device is very important and it should be considered early in the development of a new medical device. Medical device manufacturers must design, validate, and test packaging so that it can meet the intended sterility needs from manufacturing all the way to the surgical process. Sterility of a medical device could be the difference between life and death for a patient undergoing a life sustaining procedure.

References

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