By Liu Zhihua ( China Daily )

Six-hour procedure is a world first for the length of vertebral bodies replaced by a 3-D printed implant

Doctors in Beijing have used 3-D printing to create a new spine for a local 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 a surgery over six hours to have a 3-D 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 paralyzed.

Treatment for chordoma, a slow-growing cancer, usually involves surgery to remove the tumor 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 3-D 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 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 cage, so that when that bone fuses with the neighboring 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 3-D printed implant was customized 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 3-D printed implant also has pores that allow bones on healthy vertebrae to grow into the artificial implant and eventually to fuse with it.

"3-D 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 tumor in the axis (the second cervical vertebra), with a replica vertebra generated by 3-D printing.

More than 60 patients have benefited from 3-D 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 3-D 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 3-D printed hips joint product developed by the team, and in May the administration approved the team's 3-D printed artificial vertebral body product.

The application of 3D printing technology in medical field cannot be realized without successful interdisciplinary studies, and that means innovation plays a very important role in the research, Liu Zhongjun, the orthopedist, says.

It is a good opportunity for Chinese scientists to work hard to make world-leading achievements in such medical applications, because to some extent, scientists worldwide are competing from the similar starting line, as medical application of 3-D printing is quite a new scientific field internationally, he adds.

In 2005, scientists in Europe invented 3D-printed metal acetabular cup, a component for hip replacement, and many Chinese hospitals have been researching in 3-D printed medical implants, according to him.

The application of 3-D printing in medical treatment can also reduce the treatment cost for patients, Liu says.

In China, about 66 to 80 percent of the cost in an orthopedic surgery is due to the cost of artificial implants, and most of the high quality artificial implants used in surgeries are imported ones or are patented by foreign companies, which are very expensive compared with Chinese companies'.

Through 3-D printing, the manufacturing of artificial implants will be more productive and less costly, and thus can reduce patients' surgery cost burden significantly, Liu says.

Even a conservative estimate suggests that 3-D printed artificial implants will be of only half cost of that made by traditional manufacturing method, Liu notes.

However, to have a competitive advantage in the medical application of 3-D printing technology compared with other countries, it is urgent for the Chinese health authorities to have an efficient and comprehensive evaluation procedure to approve the clinical use of such 3-D medical products, Liu says.