Over recent years, the application of additive manufacturing (AM) technologies in support of craniomaxillofacial surgery has increased. German company Karl Leibinger Medizintechnik has utilized the M2 cusing metal AM platform from Concept Laser for the production of patient-specific, individual craniomaxillofacial implants.
Like many companies utilizing AM technologies, Karl Leibinger Medizintechnik has been reticent in talking about its work with the LaserCUSING process, Concept Laser’s proprietary name for the selective laser melting (SLM) process. Until now! The medical implant company has been working with additive tech since 2013, but Karl Leibinger Medizintechnik’s history dates back to 1979 when it first began developing implants for craniomaxillofacial surgery as part of the KLS Martin Group.
Craniomaxillofacial surgery is all about the head and the face, and as such, it is very, very personal and central to one’s sense of self. Moreover, four of our five senses are located in the head and on the face—sight, hearing, smell and taste—meaning that severe craniomaxillofacial trauma or deformities impact patients in myriad ways, both physically and psychologically. Craniomaxillofacial surgery involves procedures for correcting such injuries and deformities, and the work of Karl Leibinger Medizintechnik now centers around developing specific individual implants for correction through distraction and osteosynthesis to achieve better outcomes for patients.
Distraction osteogenesis can be traced back to the Russian surgeon Gavril Ilizarov, who used it for the first time in the 1950s, and involves the extension of bones. In layman’s terms, it can be explained thus: sometimes a bone ‘forgets’ to grow and the distraction osteogenesis procedure ‘reminds’ the bone to grow again and encourages it to fulfil the genetically prescribed ‘blueprint’. The procedure became established in the West at the end of the 1980s and today it is impossible to imagine the clinical practice of craniomaxillofacial surgery without it. KLS Martin has developed numerous innovative distraction systems to support this technique. Distraction is usually carried out in the midface and on the jaw.
Another key procedure used in craniomaxillofacial surgery is titanium osteosynthesis, which 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 today one of the world’s leading specialists in this field.
Today, craniomaxillofacial surgeons essentially work with three types of implants: plastic, deep-drawn metal sheets or titanium (mesh, solid and now also additive manufactured). 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. Titanium implants allow the bone structures around it to grow and is therefore highly suitable for implants, particularly in combination with lattice structures that can be made with AM. Depending on the indication, titanium implants are likewise developed individually and manufactured conventionally as a mesh or as a high-strength solid reconstruction version.
Frank Reinauer is the head of innovation and production of Biomaterials at Karl Leibinger Medizintechnik and consistently relies on AM for the production of individual implants made from titanium. He highlighted the fact that significant advances had been made in the field: ‘We had 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.’
Initially, there was the costs hurdle to overcome, however as Reinauer pointed out: ‘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. In our case—we are an owner-managed company—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.’
This decision, balancing the desire for innovation and the assessment of risk, proved to be a fruitful one, as 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 in an operating room, the amount of time saved with tool-free manufacturing was significant. However, most important was the strategic decision to focus on developing titanium implants specifically for individual patients, which is a giant leap forward for clinical practice. The increasing spread of these implants around the world is reflected in the fact that they are now a significant revenue driver for the company.
As the company embarked upon metal 3D printing, it was of course necessary to overcome a number of process validation hurdles. According to Reinauer: ‘It took around nine months to get through this preparatory phase because the regulations and general conditions in medical technology are extremely meticulous.’
Initially, the CE mark has to be acquired, and the DIN Standard 13485 and guidelines of the US Food and Drug Administration (FDA) have to be complied with.
Reinauer continued: ‘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.’
Made to measure implants
Once the company had started using metal 3D printing, it very quickly became apparent that laser melting was the method of choice for titanium osteosynthesis. A true metal 3D printing advocate, Reinauer said: ‘Now it is even possible to produce large-scale reconstructions with complex geometries. In addition, the geometric freedom can also cater for specific aesthetic requirements.
‘For the surgeon, it is not just about restoring functionality but also always about the aesthetic 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.’
Metal 3D printing 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.
Reinauer has drawn attention to another very important aspect in favor of additively manufactured titanium implants and that is the patient-specific geometry and precision fit. Ultimately, this allows for a high level of functionality.
The surgeon can use imaging techniques such as computed tomography (CT) or magnetic resonance imaging (MRI) to cater for the specific anatomy of an individual patient. The engineers from Karl Leibinger Medizintechnik process this data to create STL data that serve as the initial data for 3D construction and manufacturing on an M2 cusing platform from Concept Laser.
The M2 is designed in line with ATEX guidelines and thus makes it possible to process reactive materials like titanium or titanium alloys safely. In the opinion of Reinauer: ‘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.’
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.
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, which is a web-based platform and 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 patient-specific implants, anatomical models for optimum pre-surgical 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 offers a complete implant kit which can be installed quickly in an operation environment. Before making the decision to fabricate, the doctor sees a draft design and a price quotation. Karl Leibinger Medizintechnik is able to supply additively manufactured implants for an operation within a week. The patient-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.