3D printer gives man a new spine

A 3D printer from Stratasys.
PHOTO: Stratasys

Doctors in Beijing have used 3D printing to create a new spine for a man after five cancer-riddled vertebrae were removed from his body. The procedure is a world first in terms of the length of vertebrae replaced this way, the doctors say.

On June 12 the man, surnamed Yuan, 40, of Beijing, underwent surgery over six hours to have a 3D-printed implant of multiple thoracic and lumbar vertebral bodies, measuring 19 centimeters, inserted into his spine.

In an earlier operation lasting eight hours, doctors had removed five vertebral posterior structures of the cancer-riddled vertebrae.

The vertebrae were affected by chordoma, a cancer that can occur anywhere in the spine and skull. The surgery's success means he is able to live a normal life after he recovers. With traditional treatment, doctors say, even in the best of circumstances he may have been left paralysed.

Treatment for chordoma, a slow-growing cancer, usually involves surgery to remove the tumour first, before using chemotherapy or radiotherapy if necessary.

"Chordoma is not that rare for us," said Liu Zhongjun, director of the orthopedics department at Peking University Third Hospital, where the surgery was performed.

"What is rare in this case is that the cancer had affected so many vertebrae. Without 3D printing technology it would have been impossible to treat him."

In the first operation in mid May, back sections of Yuan's cancer-riddled vertebrae were removed, and the surgeons attached four titanium rods to what was left of the back part of the spine using titanium screws. These rods were screwed in at the other end, on the front of the spine, still bearing cancerous vertebrae, to make everything stable.

It was deemed too dangerous to remove sections of vertebrae on both sides in the one operation.

In the second operation the front parts of the vertebrae were finally removed and the 3D-printed implant was then put in place.

There had been no reports about the removal of such a large section of spine in one patient anywhere in the world, and the medical team needed to be highly skilled and experienced to deal with any emergency during the two operations, Liu said.

The void left in the spine after the front part of the five vertebrae was removed would have been too large for any existing titanium mesh cage, which is traditionally used in such surgeries. Even if it had existed it would have been straight and ill-suited to Yuan's spine.

Also, with normal titanium mesh cage, doctors usually put crushed bone in the mesh, so that when that bone fuses with the neighbouring bones the implant becomes stronger and firm enough to support the spine.

In Yuan's case this method was judged to be too risky because of the size of the implant needed. Any movement of the implant would damage the spinal cord and nerve roots in the spinal channel.

Yuan's implant was customised to cope with the curvature of his spine, and doctors designed special joints to attach it firmly to the titanium rods, which made the two parts of the implant a strong whole that is firm and is very supportive of the spine.

The 3D-printed implant also has pores that allow bones on healthy vertebrae to grow into the artificial implant and eventually to fuse with it.

"3D printing technology in orthopedics is promising, as it is in many other fields," Liu said.

After the surgery, Yuan was transferred to a normal inpatient ward rather than an intensive care unit because he lost less blood than would have been the case with traditional implant surgery. He is recovering much more quickly than expected, the doctors say.

In August 2014 the hospital treated a 12-year-old boy suffering from a rare tumour in the axis (the second cervical vertebra), with a replica vertebra generated by 3D printing.

More than 60 patients have benefited from 3D-printed orthopedic implants in the hospital, Liu said.

Led by Liu, the hospital's orthopedics department started studying the medical application of artificial vertebral body products by 3D printing in 2009, in collaboration with a medical device company in Beijing that owns an imported 3D printer.

The medical team provided designs based on their clinical experience and understanding of surgical needs supported by medical images, and the company digitalized the design through software the company developed for printing.

Animal trials on sheep started later, which proved the implants were safe, and clinical trials began in late 2012.

Last September, the China Food and Drug Administration approved the use of 3D-printed hips joint product developed by the team, and in May the administration approved the team's 3D-printed artificial vertebral body product.