Healthy outlook

Choosing failsafe fastening technologies for the medical sector can both save money and protect patient health


When it comes to medical equipment, failure is not an option. From devices such as joint implants to wall cabinets in sterile areas, when life or quality of life is at stake, medical equipment must be both reliable and fit for purpose.

However, the many demands of the industry mean that traditional fastening systems may not be suitable for many applications. In response, fastening manufacturers working in this area have developed a range of innovations that are both robust and reliable.

With the number of hospital-borne infections such as MRSA on the rise, ensuring that all equipment and fittings are biohazard-free is essential, meaning they must be capable of being cleaned repeatedly and thoroughly.

A new swing-handle developed by Dirak — although originally designed for the telecoms sector — is proving popular in the medical industry owing to its resistance to cleaning damage. The product has a flush-design and is specifically for use in applications in which corrosion resistance is vital. This allows it to be cleaned over and over again without affecting performance.

On the inside, components are protected by a stainless steel screw-on cap, while on the outside the locking cylinder is protected by a stainless steel dust cover to prevent dirt, moisture, and other elements from damaging the locking mechanism. The swing-handle also meets the requirements of the IP 65 standard for resistance to water and dust.

Importantly for the medical sector, protection from vandalism is provided by the flush design and the tight gap between the handle and its housing. This means it can be used for secure units such as medicine cupboards.

‘The handle can withstand anything from salt water to caustic soda,’ said David Hayes, Dirak’s general manager. ‘As the design is flush there are no little areas where dirt can be trapped and cause a medical hazard. Although designed originally for another market, the fact that it is clean and hygienic means the medical sector has found it very attractive.’

In an industry where equipment must be fully reliable, fastener failure must naturally be avoided at all costs. However, an inadequately torqued fastener can vibrate or work itself loose.

Conversely, if the tension is too high then the fastener can snap, or strip its threads. To avoid this, Southco has expanded its range of constant torque position control hinges to provide greater torque control functionality in many medical and hospital-based applications. The ability to position and hold doors, displays, and other components without gas struts or secondary mechanical supports is a major contributor to reducing component and manufacturing costs.

‘Southco is committed to meeting the medical industry’s standards for safety, speed and precision while contributing to the cost efficiencies expected by healthcare customers,’ said Ulrike Sturman, the company’s industry marketing manager.

‘These hinges offer long performance life with consistent high torque delivery. They have been successfully designed in a broad range of applications such as examination and imaging equipment.’

Among the latest products from the company is the CEMATM ST series of constant torque position control hinges. As well as being designed to offer long performance life without adjustment owing to their durable design, the range offers smooth operation.

Southco has also recently introduced components including the Dzus Lockwell Quick Release Pin, claimed to provide safe and quick maintenance operation through one-handed installation and removal. The product’s reliability is certified to aerospace and military standards, and because it is made of stainless steel — which can be cleaned without fear of corrosion and failure — it is fully compliant with hygiene requirements.

Owing to the demands of the industry, any fastener must be capable of handling repetitive loads, shock and also resistance to vibrational loosening. However, many traditional fasteners can be susceptible to self-loosening rotational movement, stripping, and shearing, particularly as in many cases, the vast proportion of the fastener’s load falls on the first two threads, making failure more likely.

Much research has gone into finding a solution to this problem, to ensure the fasteners used in medical equipment have a higher rate of reliability.

Spiralock has re-designed the ID, or female thread form, with a unique 30º wedge ramp at the thread’s root. ‘Our focus in the medical industry is to apply our self-locking thread form to a variety of applications that specify a threaded design,’ said Bob Ucman, medical application specialist at Spiralock.

‘Medical device manufacturers that incorporate a thread form into their products have to take into account a number of considerations. They are looking for proven technologies and suppliers that offer consistent product performance, traceability, fast prototype and production turnaround times, flexibility in the development stage, reliable deliveries and overall threaded joint cost effectiveness.’

‘Spiralock is constantly being challenged by its customers to apply its thread technology to a variety of threaded fastener applications from spinal to hip implants, from MRI machines to fluid pumps,’ added Ucman.

As a result, the company has developed a wire-threaded Drive Notch insert that can be used to create a locking thread in soft materials without the removal of an installation ‘tang’, such as those currently common in the industry.

Loosening of threaded joints in the body or on surgical equipment during surgery is unacceptable as there is no way to re-tighten implant devices after implantation. This means loosening failures during use could be catastrophic.

Ucman said, therefore, that a good fastener must be able to provide joint integrity robustness. ‘In many cases medical threaded joints do not have much real estate to work with,’ he explained. ‘They will require a robust fastener or threadform that can achieve the clamp force needed to maintain the integrity of the threaded joint.’

By making medical implants or devices easy to assemble, a good fastener can also minimise surgery times, translating into fewer patient complications and reduced recovery times.

It can therefore be seen that in choosing the right fastening technology for everything from fixtures and fittings to implantable devices, the medical sector can both save money and protect patient health — delivering benefits to all.