Implant encourages tissue growth

A new device made from silk protein could help regrow cartilage in injured knee joints.

The FibroFix implant is designed to replace the menisci, the parts of the knee that act as shock absorbers, which are often partially removed if they are torn to prevent further damage.

As well as replicating the functions of the menisci, the device has a porous structure that encourages and supports the growth of new tissue, helping to prevent arthritis.

Because it doesn’t contain blood vessels, the meniscal cartilage doesn’t easily heal itself, and without it, the articular cartilage that links the bones in the joint begins to wear away, leading to osteoarthritis.

‘The patients who suffer from this more than anyone are young active males between the ages of 17 and 35, so then you have patients who have a crippling knee condition quite early on in life,’ said Nick Skaer, chief executive of the company behind the device, Orthox.

‘With osteoarthritis, the only solution is replacement of the knee joint, so you’ve got a real issue because you can’t put a replacement knee joint in someone such as Andrew Flintoff [who has suffered a torn meniscus] because it will wear out after 10 years and you’ll need another one.’

The key to creating the device was developing a material using a protein extracted from silkworm silk and formed using chemical and physical processes similar to those used by spiders. This was based on work by the Oxford University zoology department.

‘It has the mechanical properties and surface characteristics of a meniscus so it is very stiff but very resilient, and it’s very good at absorbing shock and has a very smooth surface,’ added Skaer.

‘It also has an 85 per cent porous body and is made out of silk protein, which has strong similarities to human proteins such as fibronectin, which are found in cartilage and bone. So it’s a porous and familiar substrate for cells to grow on and into.’

The FibroFix will be cut to the size of the removed tissue and sutured into place through keyhole surgery. Although the material is resorbable, meaning it can be broken down and absorbed by the body, the lack of blood supply to the meniscus means the Orthox team does not expect the device will need to be replaced at a later date.

The firm hopes to launch the device to market in 2013 following clinical trials planned for next year. The Technology Strategy Board has just awarded Orthox £264,000 to fast track the device through to regulatory approval, as part of a recently announced £5m wave of funding in regenerative medical technology.

This takes the total funding of R&D for the device up to around £2.2m, including a £1.6m translational award from the Wellcome Trust made in February 2009.

The device also builds on an estimated £3m worth of research carried out by Orthox’s parent company Oxford Biomaterials, which has been developing the silk-based material since 2002.

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