Mixed double

All-in-one bone cement mixing device is claimed to speed up bone surgery and help make theatres more sterile. Siobhan Wagner reports.

It might look like a simple glue gun, but a bone cement mixing device made from a plastic metal substitute, is helping to provide surgeons with a fast and easy method of mixing and injecting bone cement used to affix implants and remodel lost bone.

The design of BoCeMix, from Italian medical device company Bidoia, integrates mixing and injecting components. Swiss engineer Ernst Poppe of DuPont Engineering Polymers, which invented and produces the device’s material, Delrin, said: ‘To go from mixing to applying you don’t have to do anything apart from pulling the device’s trigger ring and start applying it.’

BoCeMix is made from five injection-moulded parts of unreinforced Delrin, an acetal resin engineering plastic. This is lightweight, low-friction and wear-resistant and has been used in various other applications for years as a metal substitute.

The designers behind BoCeMix say Delrin’s natural elasticity eliminated the need for any metal pieces on the device. While traditional bone cement injectors may require a metal return spring for the trigger, BoCeMix uses a moulded plastic leaf-spring.

‘Getting rid of some metal is always beneficial,’ said Poppe. ‘When you have a metal component, it constantly needs re-sterilising and must be protected against corrosion.’

Bone cement is supplied to the mixer as a powder with liquid methyl methacrylate. When mixed, these substances yield a dough-like cement that gradually hardens. When injected into the human body for procedures such as arthroplasty, the cement acts more like a grout than a glue. Although sticky, it primarily fills the spaces between the prosthesis and the bone to prevent motion.

Bidoia marketing manager Dr Roberta Bidoia explained how the device works in mixing and injecting these cements. First, she said, surgeons are able to monitor the mixing in motion because of the device’s transparency. ‘You can easily see the blades pivoting on the ribbed driving shaft, back and forward, as if you were preparing mayonnaise,’ she said. ‘This transparency allows you to be sure it mixes perfectly.’

BoCeMix can be powered either manually or electrically, whereas most mixers are usually only manually powered.

When the surgeon believes the cement is ready for injection, said Bidoia, he or she pulls the device’s trigger ring and starts to press the handle, which pushes the piston slowly downwards, all through the length of the driving shaft.

The device is claimed to be able to ensure better quality cement by eliminating air and gas bubbles from mixes. It operates with a constantly- applied vacuum so that the cement is always under vacuum conditions from the start of mixing to the beginning of insertion.

The device’s all-in-one design also helps makes surgery a more sterile procedure because the cement does not come into contact with the air or any other instrument after mixing. It is also entirely disposable and meant for single use, which means there is less chance of contamination. In addition to its sterility, surgeons will appreciate BoCeMix’s fast 60-minute preparation time for mixing.

‘Surgeons have to work fast, and the operating room is quite a stressful environment,’ said Poppe, adding that the device also delivers on another high priority of surgeons — efficiency. ‘The mixing just has to work. They can’t check and re-check the cement five times. When they mix it, it must be how they want to have it,’ he said.