Engineering Insight

Last year, a team of experts gathered in Hasselt, Belgium, to develop a unique solution to an 83-year-old woman’s bone infection. The collaboration resulted in the replacement of her mandible with a 3-D printed custom implant, said to be the world’s first such procedure. The project required the team of physicians and researchers to work closely together during a short timeframe.

The patient had visited Dr Jules Poukens (Orbis Medical Centre, Sittard-Geleen, Netherlands) with a rapidly progressive and serious bone infection. Poukens soon realised that a conventional treatment involving removal of the damaged bone would not suffice because of the severity of the infection.

Another option used for large defects of the mandible is to reconstruct it with a vascularised bone transplant.

“In our case, the condylar heads, which are part of the tempero-mandibular joint, also had to be reconstructed. A combination of the bone transplant with some kind of metallic implant was imperative,” says Poukens. “Since this was an older lady and since part of the joint had to be reconstructed, a custom implant that would reconstruct the entire mandible was an obvious choice.”

The 3-D printed custom-made implant was coated with hydroxyapatite.

This case was unusual because the patient needed a complete mandible replacement. Concerned that the infection would spread to neighbouring anatomical structures, Poukens contacted Sirris (Brussels, Belgium), a nonprofit organisation providing expertise to the Belgian technology industry. Poukens asked for help to quickly bring together and coordinate a team of experts that could tackle the challenge before the infection spread.

“Input from medical doctors, research institutes and companies was necessary in order to design and manufacture such a complex implant in such a short timeframe,” says Poukens.

Carsten Engel, Head of Medical Affairs at Sirris, was brought in to coordinate the project and to maximise interactions between surgeons and engineers.

Language barriers
“The challenge for engineers is always to understand the language of surgeons, and [vice versa]—they have an overview of the manufacturing process but they lack technological understanding, so bringing both worlds together is always a challenge at first,” says Engel.

While additive manufacturing has been used before to reconstruct parts of the skull or the mandible, the use of a custom implant to reconstruct the complete mandible represented a new approach. “This is a new kind of implant since the entire mandible is replaced by the implant, and the mandible is in motion more or less 24 hours per day,” says Poukens.

The treatment approach was developed at University of Hasselt (Hasselt, Belgium) in cooperation with Orbis Medical Centre and engineers from Xios University College (Diepenbeek, Belgium), Sirris, Xilloc Medical bv (Maastricht, Netherlands), and the Catholic University of Leuven (Leuven, Belgium). Manufacturing by additive technology was performed by LayerWise (Leuven, Belgium), which produced the titanium implant using additive laser melting and prepared the implant’s dental components. Cambio-ceramics (Leiden, Netherlands) coated the implant with hydroxyapatite, a bio-active bone substitute.

“Every aspect of the implant has a function,” says Engel. “We had to consider the aspects of the ligaments that had to be fixed to the implant, the specific nerves that had to go through the implant and of course other critical aspects. The timeframe was a challenge, as well, since we had to operate very fast.”

The patient went into surgery in June 2011. Surgeons replaced the inflamed mandible with the custom implant. Since the implant was designed to fit the patient’s anatomy, it did not need readjustments during surgery, which shortened the surgery time. A typical reconstructive procedure takes between 10 and 20 hours and requires the patient to stay two to four weeks in the hospital to recover. This procedure took four hours and the patient was able to go home after four days.

Shortened surgery time reduces the likelihood of complications during and after the procedure. It also cuts hospital costs such as surgeon reimbursement, operating room occupation, anaesthesiology and postsurgery recovery. Because of these benefits, the demand for custom implants is increasing, says Engels.

Additive manufacturing and 3-D printing accelerate the production of custom implants compared with other technologies. In addition, the implants can be produced using the same equipment as standard implants.

Engel is confident that 3-D printing will revolutionise medical device design.

“Today we show the metal applications, but we are already working on more advanced technologies and materials, such as biodegradable ceramics and polymers, and we will combine those with stem cells as well,” Engel says. “The day will come when we will only use stem cells on biopolymers for organ printing. Printing arteries, skin and even an entire heart or kidney will be possible.”

However, the market for custom implants is not yet seeing tremendous growth, as these are new technologies lacking widespread adoption.

“Few medical centres in Europe have extensive knowledge of and expertise in [the use of] these implants in cranio-maxillofacial surgery,” says Poukens. “Knowledge about these kinds of implants has to be disseminated throughout the medical community.”