CLEANTOOLS

"Crevice-free, high reliability bi-metallic surgical instruments manufactured from shape memory alloys"

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 Obiettivo del progetto (Objective)

'Flexible medical instruments such as bone reamers are currently constructed from multiple parts in dissimilar materials, which have very different properties. The current method of linking these parts together is by mechanical coupling. Effective decontamination of such instruments is challenging but is critical to avoid cross infection between patients. The geometry of the instrument assembly (particularly bone reamers and similar tools used in joint implants) have crevices at the joints which are difficult and expensive to clean and fully sterilise. Welded instruments would eliminate this problem.

Approximately 7000 cases of MRSA infections were reported in UK hospitals during 2007 and similar issues are prevalent across Europe. Such infections are of particular concern in post-surgery patients. The CleanTools project aims to develop technology which will reduce this issue by making surgical instruments easier to clean and disinfect. The crevice between stainless steel cutting heads and Shape Memory Alloy (SMA) flexible shafts currently makes decontamination challenging, time consuming and chemically intensive. Additionally there have been instances of cutting heads becoming detached from the flexible drive shaft during use, causing undue implications in theatre and potential long term impacts on patient quality of life.

The desirable materials for these tools, such as SMAs and stainless steels, are challenging to weld and their properties are severely degraded when they are melted in conventional welding. CleanTools will provide a method for the manufacture of surgical instruments containing SMA materials though the use of rotary friction welding (RFW). RFW is a low heat input solid phase welding technology that will preserve the properties of the materials in question. CleanTools will improve the function of flexible surgical instruments, reduce the required cleaning and disinfection effort, improve reliability and reduce the cost of manufacture within Europe.'

Introduzione (Teaser)

Many flexible tools used in orthopaedic surgery are made of multiple materials linked by mechanical coupling. Using a no-melt welding process instead promises to improve sterilisation of hard-to-reach places.

Descrizione progetto (Article)

Bone reamers are used to form or enlarge holes in bone prior to insertion of prostheses. They are made of stainless steel cutting heads and shape memory alloy (SMA) flexible shafts. Mechanical coupling creates crevices that are difficult to clean and sterilise, increasing the risk of infection and, increasingly, of antibiotic-resistant infection. Welding could eliminate the crevices and contamination but the properties of stainless steel and SMAs are severely degraded when melted.

To solve the problem, scientists launched the EU-funded project http://www.cleantools.de/ (CLEANTOOLS). The team is exploiting rotary friction welding (RFW), a novel solid-state process that softens materials with friction heat and coalesces them with compressive force.

Utilisation of RFW will require careful consideration of the materials for biocompatibility, service requirements and weld properties. In addition to legislative and literature reviews, researchers conducted experimental tests pointing to the need for an interlayer between the SMA and the stainless steel.

Numerous weld trials have been conducted with the selected materials to optimise weld parameters to achieve required joint strength and ductility. Having demonstrated consistent tensile and guided bend test results, the team is now investigating commercialisation opportunities for this novel technology.

CLEANTOOLS is on its way to delivering a method for producing surgical instruments with enhanced function and ease of cleaning. Exploitation of RFW will improve reliability, decrease manufacturing costs and reduce patient infections for major benefits across the board.