The magic implant that heals bones – then disappears

An IMPLANT that helps heal broken bones then dissolves once it has finished could transform the care of fractures. Researchers in the U.S. have devised a special type of plastic that mimics the structure of normal bone to help with delayed healing or ‘ non- union’, where broken bones fail to fuse properly and occurs in roughly 5 per cent of all fractures.

In these cases, surgery is needed to help the bones knit back together.

A metal or plastic cage is used to bridge the gap between the broken parts and hold the bones in place, and then grafts of bone tissue are inserted (from another part of the body, typically the pelvis, or using donor bone) to speed up healing.

However, this means the patient needs multiple surgical procedures as the supportive cages have to be removed once the bone is healed, increasing the risk of complications.

Patients also cannot be scanned properly if they have a cage in, as the metal shows up as a shadow on MRI and CT scans.

Unlike normal bone grafts, the new material, created by a team at Beaumont Hospital Royal Oak, Michigan, should be strong enough to hold the broken bones in place without any additional support.

It also stimulates cells involved in bone healing.

As time passes, these cells use the dissolvable plastic as a scaffold to grow into. As the new tissue forms, the implant material dissolves, leaving healthy, healed bone.

How long this process takes is likely to depend on the type of fracture — different bones heal at different rates. For example, a wrist fracture takes six to 12 weeks while a spinal fracture can take 18 months to heal.

The dissolving implant should mean patients don’t need further surgery once it is inserted. It i s made f rom corn starch and a type of volcanic ash clay and is injected with carbon dioxide gas bubbles.

The resulting material is rigid but looks like foam, similar to the structure of bone.

In a recent lab study, published i n the j ournal nanomedicine: nanotechnology, Biology and Medicine, the material was shown to help new bone tissue form.

The effect seen was similar to when doctors use bone grafts and metal implants. The next stage is to test the material in patients, which could take a few years to complete.

commenting on the research, Robert Lee, a consultant orthopaedic and spinal surgeon at the Royal national Orthopaedic Hospital in Stanmore, says this material is novel and has significant potential.

‘ This overcomes problems associated with having to harvest bone from another part of body and the risks associated with that surgery — harvesting bone from the pelvis can be painful and leave the patient with significant side - effects,’ he says.

‘If it does work, patients would be able to have post-operative scans such as MRIs without the metal cages distorting the images.’

The challenge is that the material needs to be strong enough to hold bones in place exactly where they need t o be until t hey have sufficiently fused, and ‘dissolves’ at the right time.

‘while it may be strong enough to replace metal cages safely, it is not completely clear how the material would induce bone fusion — more research is needed to understand this process,’ adds Mr Lee.

MEANWHILE U.S. researchers have developed a dissolving sensor to help monitor patients with brain injuries.

The sensor is wireless, unlike the devices that are used to monitor pressure and temperature in the brain and which are key to knowing the severity of brain injuries and checking on patients’ progress.

The findings, published in the journal nature, show that the sensor sends accurate measurements from rats’ brains and can dissolve once doctors are finished.