Silk screws to repair bone fractures

In a breakthrough, scientists have used screws made from 100 per cent silk to repair broken bones, an advance that could transform future surgeries.
Silk-based surgical implants are potentially attractive alternatives to metal and synthetic-based systems, a new study has found.
Metal devices are stiff and unyielding and 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.
Using pure silk protein derived from silkworm cocoons, researchers 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 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," said co-senior author Samuel Lin.

"Silk materials are extremely robust. They maintain structural stability under very high temperatures and withstand other extreme conditions, and they can be readily sterilised," said Lin.
"One of the other big advantages of silk is that it can stabilise and deliver bio-active 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," said researcher David Kaplan.
Researchers used silk protein obtained from Bombyx mori (B mori) silkworm cocoons to form the surgical plates and screws.

Produced from the glands of the silkworm, the silk protein is folded in complex ways that give it unique properties of both exceptional strength and versatility.
To test the new devices, the investigators implanted a total of 28 silk-based screws in six laboratory rats.
Insertion of screws was straightforward and assessments were then conducted at four weeks and eight weeks, post-implantation.
"No screws failed during implantation," said Kaplan.
The findings were described in the journal Nature Communications.