Silk-based surgical implants could offer a better way to repair broken bones

When a person suffers a broken bone, treatment calls for the surgeon to insert screws and plates to help bond the broken sections and enable the fracture to heal. These ‘fixation devices’ are usually made of metal alloys.

But metal devices may have disadvantages: Because they are stiff and unyielding, they can cause stress to underlying bone. They also pose an increased risk of infection and poor wound healing. In some cases, the metal implants must be removed following fracture healing, necessitating a second surgery. Resorbable fixation devices, made of synthetic polymers, avoid some of these problems but may pose a risk of inflammatory reactions and are difficult to implant.

Now, using pure silk protein derived from silkworm cocoons, a team of investigators from Tufts University School of Engineering and Beth Israel Deaconess Medical Center (BIDMC) has developed surgical plates and screws that may not only offer improved bone remodelling following injury, but importantly, can also be absorbed by the body over time, eliminating the need for surgical removal of the devices.
‘Unlike metal, the composition of silk protein may be similar to bone composition,’ says co-senior author Samuel Lin, MD, of the Division of Plastic and Reconstructive Surgery at BIDMC and Associate Professor of Surgery at Harvard Medical School. ‘Silk materials are extremely robust. They maintain structural stability under very high temperatures and withstand other extreme conditions, and they can be readily sterilised.’

Collaborating with Lin were co-senior author and Tufts chair of biomedical engineering David Kaplan, PhD, a leader in the use of silk for biomedical applications, and a team of biomedical and mechanical engineers.

‘One of the other big advantages of silk is that it can stabilise and deliver bioactive components, so that plates and screws made of silk could actually deliver antibiotics to prevent infection, pharmaceuticals to enhance bone regrowth and other therapeutics to support healing,’ says Kaplan.

Kaplan and his team have previously developed silk-based sponges, fibres and foams for use in the operating room and in clinical settings. But until now, silk hadn