The idea of having an irreparably damaged bone scanned, a titanium copy created in a replicator and then surgically inserted into our bodies seems more Star Trek science fiction than modern-day medicine.
But advances in three-dimensional printing and a key piece of breakthrough software mean that, within a year, this will be a reality.
It is the vision of engineer Siavash Mahdavi. Mahdavi was studying robotics at University College London. Frustrated at being unable to build the robots he envisioned in his head, he turned to sintering — where thin layers of powder are laid down in a chamber, then turned into a three-dimensional object by a laser.
Do the maths
Mahdavi started sintering the materials he needed, but faced the problem of working out the appropriate internal structure for these objects. He knew that, given all the variables, it would take a computer a lifetime to do the maths. So he designed an artificial intelligence optimisation engine to develop software that could do the calculations quickly.
In 2005 he started Complex Matters, a design consultancy that works with designers and engineers who want to use this method to make items that exploit the potential of the software.
Mahdavi’s microstructure optimisation software has arrived at a time when sintering is developing from a technology for creating rapid prototypes to a fully fledged manufacturing process. In the past six months, machines capable of printing in high-quality titanium have been developed.
One of the first practical applications of the new sintering software will be to create made-to-measure orthopaedic implants.
“Imagine a hip-bone replacement,” says Mahdavi. “A surgeon will have the existing bone MRI scanned. This information is passed via a CAD programme to the 3D printer.
“By the time the patient gets to the operating theatre, we will have printed out a medical-grade titanium bone which is an identical match to the one being replaced.”
But can we be sure they will be as reliable as existing implants? “Better,” insists Mahdavi. “Firstly, they are much lighter as, like human bone, they are porous rather than solid. And having an internal mesh means you can fuse the implant to the bone, so the natural bone will grow into the holes and lock itself in. Because it’s a porous structure, you can x-ray the implant and see how the natural bone is melding with the implant.
“And, though these e-manufactured implants are only a quarter of the weight of solid ones, the laser makes a finer material than cast metal — so it is actually stronger than the current technology.”
E-manufacturing implants could have a surprising number of benefits for the health service. “Firstly, the sintering is cheaper than both custom-made and off-the-peg prostheses,” says Mahdavi.
“It is better for the environment, as the laser only fuses the powdered metal that you need; the rest can be recycled. It should be particularly helpful in complicated surgical cases, where an expensive custom-built orthopaedic implant, which currently takes three weeks to prepare, could be replaced by a cheaper one made in two hours.”
Joint effort
Tanbir Hossain, an orthopaedic surgeon at Heatherwood & Wexham Park Hospitals in southern England, is collaborating with Mahdavi on the development of sintered implants. He is optimistic that this new technology will offer significant improvements for patients. “The problems with the current hip and knee replacements is that, over time, the contact between the bone and the implant loosens and the joint wears, due to a less-than-perfect fit. This can mean further surgery. With the sintering technology, the bespoke implant will be more securely attached to the human bone and the custom fitting should suffer less wear. This would result in fewer surgical revisions.
“We are also working on sintered titanium spinal implants,” says Hossain. “The first of these should be used in surgery in January 2009.
“In the long term, 3D printing could replace traditional implants completely. It can be used for any bone in the body. The great thing about this technology is that it allows the precise design of bespoke pieces. So if someone needs a custom-made prosthetic implant this is a very good solution.” —