German bio-engineers create 3D-printable new material – combo of bioglass and biodegradable polyester. Helps bones heal quickly with less pain. Can be fitted precisely to fit any fracture.
By Dona Suri
If you’re in Düsseldorf next Monday (November 13), drop by the medical engineering trade fair, COMPAMED. If you’re on the spot when the Fraunhofer researchers unveil and demonstrate a new material, you can tell your kids that you were a witness to history.
We’d better back up a bit.
Let’s start with Tiger Woods. A couple years ago, Woods was flying down a road near Rancho Palos Verdes (LA County, California) when he lost control of his car, crashed through the guard-rail and hit a tree. He was lucky to come out alive but the bones in his right leg – ankle, fibula, tibia – were smashed.
Bad news for anybody; catastrophic news for a professional athlete. The doctors patched him up by inserting rods into the bones and held these in place with plates and screws. In the initial operation, the doctors covered the fracture sites with bone cement. Two months later, they performed a second operation to remove the cement. (This is standard procedure because the body perceives the cement as a foreign substance and protects itself with a bone membrane known as the periosteum. The cement has to go or the bone won’t heal.) Woods was bedridden for three months and full recovery took more than a year.
Considering the extent of the fractures, his bones mended quickly. Credit that to the best possible medical attention, and to the fact that he was a relatively young man, physically fit, with no complicating conditions.
Not everybody is so lucky. One out of ten people who suffer serious fractures have big trouble: their bones don’t heal quickly or correctly, they need multiple follow-up surgeries, they get infections, they are in pain. They languish in the hospital for months and even after being discharged, they can’t put weight on the damaged limb. Therapy is time-consuming and expensive.
Imagine what it’s like having a broken bone that stays broke.
What if there were something else that could hold and stabilize the bone while it was regrowing and repairing, something that caused no infection, that the body accepted as a part of itself?
Four characteristics top the doctors’ wish list:
Biocompatible: the material performs the function of cell recruitment; it’s porous with a large surface are so that repair cells can easily latch on and proliferate.
Biodegradable: the material dissolves completely when bone regeneration is complete. Even better, it degrades at the same rate that new bone is forming.
Biomimetic: the material is just like human bone, meaning it’s a hierarchical structure comprising a ring-type matrix and matches the mechanical properties of the bone it is used in.
Bio-functional: the material speeds up the healing process by delivering drugs and promoting growth factors exactly where the bone is broken.
Impossible dream? Not anymore.
After years of research, materials engineers at Bremen’s Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM) can show the world a unique a composite material – one that not only gives the doctors everything they want, it’s also 3-D printable and can be minutely customized to precisely fit every unique fracture.
But wait … bioglass has been around for 50 years! What’s the big deal about this IFAM stuff?
Big Deal 1
The first bioglass was silica-based; the newest bioactive glasses use boron instead. Borate-based glasses produce the same results as the older silica containing glasses but react 5 to 10 times faster during the conversion process. This is the time period required for the graft to convert into hydroxyapatite which can then be remodeled into bone by the body’s natural process. By shortening the conversion time, the remodeling process can begin sooner thereby producing fully functional bone earlier than the silica-based glasses.
Big Deal 2
IFAM’s bioglass has been combined with polycaprolactone on an industrial scale. This makes it possible to 3D print customized scaffolds to fit any bone fracture.
Here’s how it works:
Doctors take a CT scan of the broken bone. This gives them a 3D image. Using this image, the 3D printer builds a scaffold that fits the bone perfectly. Because the printed scaffold is exact to the micrometer, doctors can just slide it onto the bone in the operating theater. No time-consuming, by-hand tailoring required. Every patient receives a unique scaffold.
At the site of the fracture, body fluids interact with the bioglass allowing ions to exchange with the surrounding fluids. The bioglass turns into hydroxylapatite, a chemical compound derived primarily from calcium phosphate. It is very similar to bone and it becomes incorporated into new and living bone tissue. This hydroxylapatite raises the pH of its surroundings to alkaline, which inhibits bacterial growth, and therefore the risk of post-operation infections. Being a synthetic material, it has no potential to cause blood-borne transmission disease. The scaffold bonds to the bone, stimulates and supports new bone growth and completely dissolves after about six years. The scaffold is gone, there is only bone.
Should the ratio of bioglass to PCL be the same no matter which bone is broken?
What’s the optimum proportions in the case of bone grafts?
The IFAM researchers are working on those questions and more. They want to make variations of printable bioglass to suit specific jobs and for each job, the idea is to retain the biologically positive characteristics of glass while maintaining the core strength of the scaffold.
The challenge of bone grafts is particularly interesting. Traditionally, donor bone is taken from different patient sites during surgery. In other words, the doctors must perform, not one, but several surgeries. This increases the risk of infection and the patient is going to come out of the anesthetic into a lot of pain. Bioactive glass eliminates the need for host or donor bone tissue. To substitute for a substantial amount of bone, the material of the scaffold must be in the right mix and the material must be safely anchored to the soft callus, allowing the graft to regrow without disturbance.
The future is even more exciting. Experiments have shown that bioglass has the ability to heal soft tissue that has been resistant to healing by traditional methods. It may even have the potential to help nerves regenerate.
The IFAM scientists are not there yet but they are getting closer with every research project.