3D metal printed medical implants

3D metal printed medical implants

Frank Reinauer, head of innovation and production of biomaterials at Karl Leibinger Medizintechnik, consistently relies on additively manufactured implants to manufacture patient-specific implants.

3D/Additive/Alternative Materials

The name Karl Leibinger Medizintechnik has been synonymous since 1979 with implants in craniomaxillofacial surgery. Karl Leibinger Medizintechnik is a company that belongs to the KLS Martin Group. Resorbable implants were added in 2000. The most recent development are patient-specific individual implants for correction through distraction and osteosynthesis in the event of traumas or deformities. Initially manufactured by conventional means, since 2013 these implants have also been manufactured additively. This is based on the LaserCUSING process from Concept Laser, whose M2 cusing machine is used at Karl Leibinger Medizintechnik. Behind this lies a simple basic approach, which has the ability to transform surgery for the individual patient rather than being a standard solution. To manufacture patient-specific implants, Frank Reinauer, head of innovation and production of biomaterials at Karl Leibinger Medizintechnik, now consistently relies on additively manufactured implants.

Distraction osteogenesis and titanium osteosynthesis
Distraction osteogenesis can be traced back to the Russian surgeon Gavril Ilizarov, who used it for the first time in the 1950s in Russia. Distraction osteogenesis involves the extension of bones. Sometimes a bone forgets to grow. The distraction reminds the bone to grow again. It is encouraged to fulfill the genetically prescribed blueprint. For this reason, it is usually sufficient, for example in the pediatric treatment of craniosynostosis, to perform a one-off operation in order to open and distract the ossifying skull so that the brain is given the space it needs to grow. The procedure also became established in the West at the end of the 1980s.

Today it is impossible to imagine the clinical practice of CMF surgery without it. What is more: Distraction osteogenesis is the procedure of choice in many cases. KLS Martin has come up with numerous innovative distraction systems to help to establish this technique globally in operating rooms for craniomaxillofacial surgery. There is hardly any problem that KLS Martin cannot solve with a distractor specially designed for it. Distraction is usually carried out in the midface and on the jaw. KLS Martin is one of the world’s leading suppliers of many of the essential items for operations in CMF surgery – ranging from plates, meshes, screws, pins, distractors, patient-specific implants through to lasers, HF equipment, surgical lights, and sterilization containers.

The second key concept is titanium osteosynthesis. This involves giving the bone new stability. The impetus for this advanced development in the field of osteosynthesis was provided by Professor Maxime Champy. Thanks to his revolutionary observations in relation to the biomechanics of the cranium, KLS Martin is one of the world’s leading specialists in this field. Particularly in orthognathic and reconstructive surgery, nowadays doctors must constantly face up to new challenges. A high degree of ambition and vision in combination with many years of experience is therefore absolutely crucial for developing suitable solutions. KLS Martin meets these high requirements with state-of-the-art manufacturing technologies and perfect collaboration between scientists and users.

For each individual patient rather than a standard solution
A surgeon today essentially decides between three types of craniomaxillofacial implants: plastic implants, for example made of polyether ether ketone (PEEK); deep-drawn metal sheets, titanium mesh, titanium solid; and now also additively manufactured titanium implants. Due to its excellent biocompatibility and its high resistance to corrosion titanium has gained immense popularity and has successfully established itself as the material of choice in the medical field. Other than PEEK, where there is absolutely no bone ingrowth, it allows the bone to grow and is therefore the perfect material for implants in combination with lattice structures made by additive manufacturing. Depending on the indication, titanium implants are developed individually and manufactured conventionally as a mesh or as a high-strength solid reconstruction version.

There was the obvious thought of why manufacture by conventional means if an additive approach was also possible.

 “We have of course long had our eye on the additive approach. But we also had very precise notions of what the machine needed to be capable of. After the first decade of 3D metal printing, the time seemed to have come to get involved,” Reinauer says.

However, initially there was the hurdle of investing in AM (additive manufacturing) to overcome.

“If you make a decision based purely on economics, then you shy away from the risk and tell yourself to let others try it first. But in our case – we are an owner-managed company – the management quickly recognized the future opportunities that lay in store for us. The decision to get involved was made for strategic reasons, and this was absolutely the right decision. We purchased our first AM machine from Concept Laser in 2013,” Reinauer says.

This decision, balancing the desire for innovation and the assessment of risk, proved to be a fruitful one: The complex part requirements for medical implants, even in light of very complicated rules and regulations, meant that the AM machine very quickly paid for itself. Given the pressure of time for an operating room, the amount of time saved with tool-free manufacturing should also not be underestimated. But above all the strategic decision was an important driver because an additively manufactured titanium implant for an individual patient is a giant leap forward for clinical practice. The increasing spread of these implants around the world is also reflected in the fact that they are now a significant revenue driver for the company.

Embarking upon additive manufacturing with metals
When embarking upon 3D metal printing, according to Frank Reinauer, it was necessary to overcome initial hurdles in process validation.

“It took us around nine months to get through this preparatory phase because the regulations and general conditions in medical technology are extremely meticulous,” Reinauer says.

Initially the CE mark has to be acquired. In addition, DIN Standard 13485 and the guidelines of the United States Food and Drug Administration have to be complied with.

“There are then also special regulations for certain countries. The versions of the Medical Devices Act and the Medical Devices Regulation (MDR) also provide a basis. In addition, there are of course also audits by authorities that we are required to undergo. However, once you have actually gone through this stage, this also teaches us a great deal as a manufacturer and thus gives us a crucial competitive advantage,” according to Reinauer.

Titanium as the benchmark: implants made to measure
After we started using 3D metal printing, it very quickly became apparent that laser melting was the method of choice for titanium osteosynthesis. Now it is even possible to produce large-scale reconstructions with complex geometries. In addition, the geometric freedom can also cater for specific esthetic requirements. For the surgeon, it is not just about restoring functionality, but also always about the esthetic look. The parts have high strength, and the material is biocompatible. Even those with allergies can receive titanium extremely well.

“From numerous aspects we view titanium as providing the benchmark for implant technology,” Reinauer says.

Additive manufacturing with metal also offers the opportunity to manufacture specific partial surface roughnesses of the implant so that it can fuse with the bone very quickly at the edges of the implant.

“But there is another very important aspect in favor of additively manufactured titanium implants: the patient-specific geometry and precision fit. Ultimately this means a high level of functionality,” Reinauer explains.

The surgeon can use imaging techniques such as CT (computed tomography) or MRI (magnetic resonance imaging) to cater for the specific anatomy of an individual patient. The engineers from Karl Leibinger Medizintechnik process this data to create STL data which serves as the initial data for 3D construction and manufacturing on a M2 cusing from Concept Laser.

Manufacture of laser-melted individual implants
One can refer to a digital process chain at Karl Leibinger. The parts are built up on the M2 cusing very promptly, and even large-scale parts can be accommodated in a build envelope of 250mm x 250mm x 280 mm (X, Y, Z). The M2 cusing is designed in line with ATEX guidelines and thus makes it possible to process reactive materials like titanium or titanium alloys safely.

“When it comes to processing reactive materials, Concept Laser has undoubtedly set the benchmark for safety and with a contamination-free concept for manufacturing additive parts,” Reinauer notes.

Like all machine solutions from Concept Laser, for reasons of user-friendliness and safety the M2 cusing also features physical separation of the process chamber and handling area. It is robust and suitable for three-shift operation. After the parts have been built up, the parts are heat-treated to reduce tension, and then sterilized and packaged in a Class 7 cleanroom.

Demand is growing
The use of these implants is expanding. There are currently more than 20 engineers employed worldwide on handling assignments for clinics. Karl Leibinger Medizintechnik offers surgeons a transparent order handling system. It is a web-based platform which is controlled via an APP. On the clinic site the surgeon stipulates the patient data, geometric demands and the date of the operation. In addition to the patient-specific implants, anatomical models for optimum presurgical planning can also be requested on this site. It is often also necessary to cater for special requests in the construction, for example when removing a tumor that needs to be planned on a larger scale. For complicated interventions, Karl Leibinger Medizintechnik then also offers a complete implant kit which can be installed very quickly and precisely in an operation. Before making the decision to fabricate, the doctor sees a draft design and a price quotation. This means we are able to supply additively manufactured implants for an operation within a week. The specific geometry and precision fit are crucial in the operation because they shorten the operating time, reduce the risk of the operation, and the surgeon can concentrate on the actual operation itself. The patient benefits from a safe operation and a quicker recovery.

Aspects of additively manufactured, patient-individual implants made of titanium

  • Freedom of geometry and a precision fit affect functionality and esthetics
  • Large-scale, complex structures are possible
  • Definable edge and surface texture ensure good bone ingrowth
  • Prompt, toolless manufacturing and rapid process chain
  • High reproducibility
  • Titanium is biocompatible and is noted for its high strength
  • Titanium is elastic, corrosion-resistant and temperature-resistant
  • Safe and quick operations
  • Quicker patient recovery
  • Ultimately relieves the strain on the healthcare system