Tackling the challenges of surgical sterility

Tackling surgical sterility in modern surgery

While sterilisation methods of surgical instruments have greatly reduced the chance of SSIs, the technological development of surgical systems and instruments is moving at a much faster rate than advancements in cleaning and sterilisation methods. To mitigate the risk of SSIs, developers are using three main methods to try and ensure patient safety.

1. Design for reprocessing

For simpler surgical devices, one way to reduce infection risk is to optimise the design of reusable instruments to be more suited to reprocessing methods. This should be applied to both the physical design of the instrument and the instructions provided with it.

Standards guidance on designing reusable surgical devices

There are several key standards that provide guidance on how to physically design reusable surgical devices. AAMI TIR12:2020 provides a list of key design considerations that are important for reuse, including: “risk of patient infection based on intended clinical use; physical design; material selection; human factors; cleaning; total system design; packaging design considerations, if applicable; disinfection; and sterilization.”

Meanwhile, AAMI TIR30:2011/(R)2016 lists a number of instrument design features which are difficult to re-process and which should be avoided.

While these standards are useful tools in your development, they generally focus on the negative features of existing technologies and do not necessarily provide any recommendations for improving surgical sterility.

Evaluating existing surgical devices

Another good place to start when designing a reusable surgical device is by evaluating existing instruments. When reviewing other instruments, consider whether there are any features which make it easy or difficult to clean the device. Most surgical instruments have not changed for decades, if not centuries, so their design may not be optimised for reprocessing. It is useful to talk with the hospital sterile services departments that reprocess these devices. Are there areas that are difficult to access for cleaning after use?

Design principles to promote cleanliness

When designing something which needs to be cleaned, there are several general design rules which can be followed:

• Crevices and hard-to-reach areas where bodily matter can be trapped and not easily cleaned should be removed from the design
• Surfaces should be smooth and easy to wipe clean
• Edges should be rounded wherever the device is not intended to cut or grasp tissue.

Where this is not possible, it is best to avoid introducing any new features which are harder to clean than existing instruments.

Material selection

Materials are another critical consideration in design for reprocessing. Stainless steel has historically been the material of choice for reusable surgical instruments, but this may not be suitable for the device you are developing. AAMI TIR12 states that “materials used in the construction of devices should be stable in the presence of recommended chemical agents and processing conditions (e.g., temperature, pressure, vacuum, humidity, time).”

Material data sheets may specify that your material is suitable for the cleaning and sterilisation methods you are intending to use, but the component design may not be. Higher temperature sterilisation will cause expansion of the material, for example, which may cause unwanted stresses in your instrument assembly. Different materials have different properties, which may mean that they are suitable for reprocessing on their own but not necessarily when assembled. Careful material selection, calculations, simulation and testing can be used to mitigate the chance of this occurring.

Cleaning, disinfection and sterilisation processes

As with any medical device, the functional design and development alone is not enough. For a reusable medical device, manufacturers must validate their cleaning, disinfection and sterilisation processes to ensure their device is safe for use on the next patient. The process to be followed by hospital reprocessing services must be detailed in the Instructions For Use (IFU) of the device (as required by BS EN ISO 17664-1:2021), which then needs to be followed for validation by the test house. Involving a test house in the development of your IFU is also recommended to increase the likelihood of
passing validation.

“ANSI/AAMI/ISO 17664 [15] and the FDA both state that the medical device manufacturer shall validate each process that is identified in the information supplied with the medical device. This validation needs to demonstrate that each process is suitable for processing of the medical device.” – AAMI TIR12

Cleaning, disinfection and sterilisation validation are not the only activities which are impacted when designing reusable surgical instruments. Biocompatibility testing is also influenced by reuse and should be considered.

Biocompatibility testing

AAMI TIR12:2020 states: “manufacturers of semi-critical and critical devices must show that residual chemical disinfectants and sterilants do not have an adverse effect on the biocompatibility of the device after processing is completed (see ISO 10993 series).”

Biocompatibility testing must be conducted after the intended number of uses for the instrument (plus a safety factor of 0.25). This is to ensure that cleaning chemicals and the sterilisation method have not altered the chemical composition of the material and that residual chemicals are not present which could react adversely with the patient.

In summary, reusable instruments should be manufactured from suitable materials for use, biocompatibility and reprocessing. Their design should be optimised for ease of cleaning, removal of soil and to withstand the validated reprocessing steps detailed in your device’s IFU.

2. Sterile drapes

Sterile drapes are used to prevent contact with unprepared surfaces and to maintain the sterility of environmental surfaces, equipment and the patients’ surroundings. Surgical drapes remove the need to sterilise everything in the operating room. Instead, only parts that come into contact with the patient need to undergo sterilisation.

For manual surgery, this generally does not impact the design of tools as the sterilisation of surgical instruments is still required, however, it does aid the surgical team in keeping the risk of infection low during the procedure. One area in which drapes can impact the design of surgical tools is in
surgical robots.

Robotic surgery usually involves large complex systems, including electronics such as teleoperated arms, being in close proximity to the patient. Often, these parts are impossible to sterilise, however, sterile drapes can be used to cover them, with an attachment for removable sterilised instruments.

Although sterile drapes remove the need to design the entire system for sterilisation, this does not remove all design constraints. The robotic system and drapes need to be designed with each other in mind to be successful at maintaining sterility. The drapes need to be easy to apply and remove, held in place and allow both full range of motion and a sterilised instrument to be attached.

Draping can be difficult and time consuming. Often, only the parts of the system that need to be in close proximity to the patient are draped, while the large control systems are designed to be used outside of the sterile field. Surgical robotics manufacturer Distalmotion identified an issue with this practice, as it can mean the transition to manual intervention, if needed, is slow. Distalmotion’s Dexter robot was developed to combat this challenge by creating a system that can be easily draped and operated in a sterile environment. This allows the surgeon to remain in the sterile field, enabling a smooth transition from robotic to laparoscopic surgery.

3. Single use surgical instruments

As drapes still require the sterilisation of surgical instruments, and with the challenges of reprocessing constraining design, instruments are often designed for single use. This means the instruments can be sterilised on the manufacturing line and provided to surgeons in pre-sterilised packaging to ensure greater surgical sterility. Not only does this make it easier for the supplier who does not need to worry about design for reprocessing, but it also makes it easier for the surgical team who no longer need to take steps after the procedure to reduce the presence of residual soil to aid cleaning. Instead, the instrument can be immediately disposed of.

Making surgical instruments disposable gives designers the freedom to develop the device purely for performance, without cleaning and post-use sterilisation in mind. It also increases the choice of materials, features, assembly and manufacturing methods. Additionally, it removes the risk of improperly reprocessed instruments, which could lead to an SSI and put the patient’s safety at risk.

It is a heated debate in the healthcare industry whether single-use or reusable surgical instruments, as well as other medical devices, are superior. Sustainability and cost are two of the main factors to be considered when making this decision together with time, logistics and device performance after
multiple use.

Sustainability and surgical sterility

Making surgical tools reprocessable, and hence reusable, sounds like a great way to minimise the environmental impact of surgery, however, in reality, the impacts of this are often more complex. Sterilisation methods have the potential to exceed the carbon emissions of disposable instruments. Our article on ‘how to reuse medical products sustainably’ discusses this in more detail and highlights the need for careful sterilisation process design and selection.

Although there is some debate around the carbon emissions of reusable vs disposable devices, it is clear that it is not sustainable for all surgical tools to be single use indefinitely. The amount of single use equipment in the operating theatre can be phenomenal, with theatres typically accounting for a quarter of all hospital waste. Recycling can often be named as a solution, however this alone will not solve the issue.

The cost of single use surgical instruments

In addition to the environmental impact of increased waste to landfill, the continued development of surgical systems and instruments has increased the cost of these parts, making single use a less appealing choice.

One way to combat this is to make systems semi-reusable – an assembly of reusable and disposable parts. This is commonly seen in laparoscopic instruments, where the handles are often reusable as they can be easily cleaned and sterilised, while the instrument tips with hard-to-reach areas are detachable and disposable.

What does the future of surgical sterility look like?

While functionality of surgical tools is a key factor in the success of surgical procedures, sterility is essential for patient safety. If tools have not been designed with surgical sterility in mind, a risk of infection is introduced, which can lead to more treatment being required and longer hospital stays – in some cases, even leading to death. Therefore, it is vital that sterility is designed for and assessed throughout surgical device development.

There’s no denying that single use instruments are currently the best way to minimise the risk of infection, however, there are environmental and cost concerns associated with these. Ultimately, the industry should aim to create highly performing, fully reusable surgical devices compatible with low-energy sterilisation methods. While achieving this poses challenges to the surgical industry, we are already witnessing innovative solutions to this issue. Sterile drapes are allowing parts of complex instruments to be reused without the need for reprocessing, while tools designed with reprocessing in mind allow them to be effectively cleaned and sterilised after use. The risk of SSIs will only be reduced if we continue to prioritise surgical sterility and patient safety in the development of new devices.