No metal plates or screws needed: a new 3D-printed ceramic implant mends broken legs by holding the fractured parts together, then turning into natural bone.
The implant has the same strength as real bone, and is made by at the University of Sydney in Australia and her colleagues. In previous studies, they showed the material could completely heal in rabbits. Now, in work yet to be published, they have shown it can also repair large leg fractures in sheep.
The eight sheep in the study were able to walk on the implants immediately after surgery, with plaster casts helping to stabilise their legs for the first four weeks. The researchers saw complete healing in 25 per cent of the fractures after three months and 88 per cent after one year. X-rays showed that as the real bones grew back, the scaffolds gradually dissolved away. 鈥淭hey got their old bones back,鈥� says Zreiqat.
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Good as new
The team found that the sheep tolerated the implants well and that there were no toxic side effects as they dissolved. They probably melded easily with existing bones because they had a similar composition, says Zreiqat. 鈥淭he body can鈥檛 tell the difference,鈥� she says.
This contrasts with many of the currently available treatments for broken bones. For example, metal leg plates and screws often cause discomfort, and bone grafts are often rejected by the recipients鈥� immune systems.
The 鈥渋nk鈥� the team used in the 3D-printing process was a mixture of calcium silicate, a mineral called gahnite, and small amounts of strontium and zinc that are found as trace elements in bone. The implants were designed to be porous scaffolds so that natural bone and blood vessels could grow through them and restore the skeleton.
Heavy lifters
Other groups are working on such synthetic bones too. For example, last year at Northwestern University in Illinois reported a 3D-printed implant that is flexible and elastic enough to fit into any bone fracture, and has been used to repair small defects in rat spines and monkey skulls. However, it may not be suitable for carrying heavy loads because it lacks the strength of real bone.
Zreiqat鈥檚 results are impressive, says Jakus, although their rigidity could mean they are not be able to adequately repair complex defects. One advantage of his team鈥檚 flexible implants is that they can easily be cut, folded and squeezed into shape during surgery. 鈥淪urgeons love this quality as it makes the material easy to utilise in a variety of scenarios,鈥� he says.
The next step for Zreiqat and her colleagues is to test the implants in people. The aim is initially to use them to repair spinal defects and broken jaws, then larger fractures in load-bearing bones like in the legs and hips. 鈥淲e believe it will be the first synthetic material to combine both the mechanical and biological advantages of real bone,鈥� Zreiqat says.
