After an accident or already at birth, permanently or for a short period – the situations where implants are needed are as diverse as the implants used. Thus, some questions arise quickly: Which material is useful in which situation? Which material should be used?
COMPAMED-tradefair.com talked with Thomas Samyn about patient specific implants, additive manufacturing and different materials.
Mr. Samyn, you offer various implants for craniomaxillofacial (CMF) surgery: implants for titanium osteosynthesis, resorbable implants or patient-specific implants. How are they different?
Thomas Samyn: We basically differentiate between patient-specific and standard solutions. Depending on the indication, you subsequently decide which material is best suited for the patient. If you need implants with load-bearing capacity such as mandible (jaw) implants, for example, you should use a high-strength titanium implant, while you could also use a resorbable material for other non-load bearing areas.
What implants are used for each specific purpose?
Samyn: Implants are essentially selected based on the indication that needs to be supported. There are different available procedures for various indications. Distinct criteria are a patient's age for example and also patient compliance. The health care system of the surgeon also plays a key role. If you are not able to bill a procedure in a respective country, the physician will probably resort to another method. The next point is that physicians run through different schools during the course of their studies and thus naturally develop a preference. If somebody was taught the distraction concept during their studies, they are likely to trust in it later on versus plate osteosynthesis, provided both procedures present a reasonable option. There are pros and cons for each procedure and there is often no right or wrong way. All roads lead to Rome.
Which material is best suited for which implant or application?
Samyn: First of all, materials are relatively limited due to biocompatibility. The bottom line is, we can fall back on certain materials depending on the expected mechanical load. These include implant steel, titanium, PEEK (polyether ether ketone) or resorbable materials.
If a patient's lower jaw needs to receive an implant, titanium is usually the only option. If a cranial implant is required, I have a choice between titanium mesh or a PEEK implant. If you operate on small children, you are almost forced to use resorbable materials, at least in oral and maxillofacial surgery. If you need to support long bone fractures where stronger forces are exerted on the structure and nothing is allowed to become ingrown, classic steel implants, which were frowned upon for a long time, are back in style. This means, you always need to ask: where am I? What do I want to do? Should it become ingrown? Or should it not grow in? The material is then selected based on these criteria. Because of the specific material properties, the same material might yield effects that are wanted in some surgeries but not in others.
The individual implants are partly manufactured using additive manufacturing processes. How does this work?
Samyn: First you need digital 3D design data that’s generated based on the patient's individual anatomy. Then you need a selective laser melting machine. It has an embedded high-power laser that melts titanium powder right at the spot where a component needs to be generated. In doing so, the powder essentially turns into a piece of metal. The laser subsequently scans the contour that’s to be produced layer by layer to where a freeform is being created. Whenever one layer has been completed, the bed that contains the powder is lowered again. Then the next layer is being added. This additive process creates a new implant. After the actual manufacturing process, the product is further processed in several steps until the final implant is completed and then made available to the hospital after it has been cleaned and purified.
What materials do you use in additive manufacturing?
Samyn: Right now we use a titanium-aluminium-vanadium alloy. In the future, we will also be able to use pure titanium, which is mechanically less rigid and is thus easier to surgically rework. We might be able to use other materials in the future, even resorbable ones.
It is essential in our field to always use biocompatible materials. That is to say, we can only resort to the few materials that are proven to be biocompatible. They in turn need to not only be available in powder or liquid form but also need to lend themselves for use in a respective additive process. All of these basic conditions must be met.
Based on today's standard, we can definitely say that titanium alloys and pure titanium work well. Resorbable materials are still in the making.
In your opinion, what will the CMF implant solutions evolve into in terms of the utilized processes, but also as it pertains to the applied materials?
Samyn: We believe that individualized medicine will become more and more important. Techniques and processes are improving and becoming more efficient, thus enabling the production of financially interesting products. In addition, better software solutions assist us in ordering, design and logistics processes. We can imagine that more patients can be treated with custom solutions in the near future.
We assume that resorbable materials will also become increasingly important. In the future, there will be materials available in the resorbable sector that have a higher load-bearing capacity so that you can also support body regions where these materials are off-limits today.
The third major trend moves away from product solutions and towards system solutions. Complex processes are being planned and simulated on the computer prior to surgery. The use of patient-specific and custom implants, for example, can assist in transferring the planning results into the surgery. That means, you first plan with software and then transfer the result to the patient using individualized surgical instruments and implants. This creates a solution that’s customized and exactly fits the patient. The idea is to achieve better, and above all, reproducible postoperative results.