The Prince of Wales Hospital is one of the earliest medical institutions to use 3D printing as a surgical aid. Dr Tang Ning, a consultant in the Department of Orthopaedics and Traumatology, has pioneered the use of 3D printing technology to perform pre-operation surgical planning. After scanning the shape and alignment of a patient’s bones, intricately detailed plastic models are made with the 3D printer. The surgeons can then plan and practise conducting the surgery using the simulated bone structure.
3D printing not only shortens the time it takes to perform a surgery and therefore reduces the amount of blood lost, it also allows surgeons to shape the metal implant so that if fits perfectly before the operation. Especially for complicated and atypical surgeries, 3D printing can play an important role in surgical planning.
Tang recalls the case of 22-year-old patient in Shaanxi who lost his left leg after stepping on a landmine when he was seven. He says the patient underwent multiple operations over the past decade that resulted in many problems: his legs were different in length, he had weak bones and supporting tissues and there were injuries left by previous implants. After considering the surgical complexity, Tang used 3D printing technology to make a plastic model of the patient’s bad leg so the complex surgery could be practised in advance.. The actual surgery was a success. “The 3D model costs about HK$3,000 … Even if we get it wrong, we can try again. But we won’t have a second chance on the patient’s body,” he says.
In another case, involving a pelvic fracture after a car accident, Tang found it would be dangerous to perform the surgery as there were complex blood vessels near the pelvis. Without 3D printing, doctors can only study the computerised tomography (CT) scans or 2D projections of a fractured bone. The real surgery itself is the first and only “drill” surgeons have. “We open a large wound in the surgery. While we take at least an hour to bend [the metal framework] into the patient’s body, the wound keeps bleeding,” Tang says. In the mock surgery using a 3D model, the surgeons can simulate the difficulties of the operation and familiarise themselves with the unique anatomy of each patient.
As the application of 3D printing in surgical planning develops apace, medical researchers and engineers are looking further ahead by asking whether 3D printing can be used to produce joints and bones to be implanted into the human body?
Professor Arthur Mak Fuk-tat, division head of biomedical engineering at the Chinese University of Hong Kong, believes one of the major future developments of 3D printing will be the manufacture of customised and patient-specific implants to replace traditional ones. He says that, for example, typically in operations to remove tumors from hip joint bones, Asian patients have to order implants from Europe. However, the size and curve of hip joints are different for Caucasians and Asians, leading to problems like the implant not matching perfectly with the Asian patient’s bone structure.
“It’s not just about size S, M and L… It will be harder for doctors to place the implant inside the bone marrow if the size doesn’t fit,” Mak says. He is hopeful that 3D printing can revolutionise the field, so that each implant is precisely designed and created for each patient. In August, surgeons at the Peking University Hospital in Beijing successfully replaced a section of spine of a 12-year-old bone cancer patient with a 3D-printed implant. This opened up possibilities of developing 3D-printed replacement bones.
Despite medical breakthroughs using 3D printing around the globe, there are still technical difficulties researchers like Mak have to solve. “3D printing which uses plastic can’t make artificial hip and limb joints. There is metallic 3D printing, but it’s very expensive,” he says. 3D-printing of metal and bio-compatible materials can cost millions of dollars, while the quality and non-toxicity of the implants printed cannot be guaranteed at this stage.
Before 3D printing can become a mainstream production method for biomedical devices, there has to be clinical observation of whether 3D-printed implants will harm patients’ health. “It can be devastating if the device breaks down in a human body,” says Mak, “but I think the problems will be resolved sooner or later, it’s just a matter of time. It’s a question raised but not a barrier.”