Stefano Caselli, founder and CEO of Tsunami Medical, has a vision to drive spinal technology innovation forward. He uses GE Additive’s laser-based (DMLM) metal additive technology.
Caselli’s investment in and early adoption of additive technology continues to bear fruit — which is driving business growth and global expansion.
Since the beginning of 2021, the Mirandola, Italy-based company has launched nine 3D-printed titanium spinal-fusion implants and a pedicle screw and rod system.
The ability to bring these new products to market builds on the strong and trusted working relationship Caselli and his team have built with surgeons over many years and demonstrates the acceptance and use of 3D-printed titanium implants by the wider orthopedic community. That close collaboration with surgeons and clinical studies focusing on implant design that promote bone ingrowth are cornerstones of Tsunami Medical’s R&D strategy.
“It’s well known that the orthopedic sector has been a champion for metal 3D printing for many years, and over time, trust in additive manufacturing has grown,” said Caselli.
“The deployment of metal additive manufacturing continues at pace in orthopedics. Surgeons and healthcare professionals have become advanced expert users, thanks to their early adoption of the technology. Their comfort level, expertise and desire to innovate result in optimal conditions for accelerating product development and bringing them to market,” he added.
Materials and mobility matter
Tsunami Medical’s second generation of implants incorporates many of the design and manufacturing advantages offered by metal additive technology to drive innovation in the orthopedic sector further.
The company’s intervertebral (or interbody) bone ingrowth cages replace the vertebral disc to facilitate a bony fusion of the vertebral segment and retain or restore balance and stability of the vertebral column. There are several ways to approach the affected vertebral segment, so the company designed cages for each specific surgical approach, designing specific instruments and tools and manufacturing them using additive manufacturing technology.
Today, spinal surgery is routine for both orthopedic surgeons and neurosurgeons, delivering rehabilitative solutions for spine pathologies, which include but are not limited to, vertebral disc degeneration, vertebral fractures and scoliosis. Caselli and his team are continuously improving implant design and challenging conventional manufacturing techniques of the past.
Early interbody cages were made from machined titanium bars. Owing to the material’s high biocompatibility and following a post-treatment that imparts the appropriate surface roughness, titanium promotes bone ingrowth.
However, titanium cages made by using conventional manufacturing, proved to be too rigid for the application, whereas a certain level of (micro)elasticity of the implant is required to initiate and accelerate bone growth. Also, these cages showed serious problems in radiological imaging by showing disturbing scattering. Both the implant stiffness and issues in radiological imaging have been resolved by cages manufactured of polyether ether ketone (PEEK), which became the industry’s standard and preferred choice of surgeons.
PEEK features good biocompatibility, mechanical strength, as well as an elasticity like natural bone. Additionally, its radiolucency also allows a good postoperative evaluation. However, ultimately PEEK did prove not to be the most suitable material for these applications after all. Although it addressed the problems of conventional manufactured titanium cages, it has been proved no bone grows on the PEEK surface. It was, therefore, necessary to reconsider the base material and manufacturing processes of interbody cages, and this is where 3D-printed titanium cages have come into play.
Using laser- and EBM-based additive technologies, it is possible to produce a trabecular surface, which is similar to the natural bone’s structure and optimal for bone ingrowth. Tsunami Medical’s unique net structure design is based on clinical experience and scientific research, which indicate that the ideal pore size for promoting bone ingrowth is between 500 and 700 microns. This is possible only using additive manufacturing.
This net structure, in combination with the geometrical design of Tsunami Medical’s cage options, offers an elasticity of the implant at least equivalent to PEEK and very close to the micro-elasticity modulus of natural bone. This is the essential requirement for facilitating rapid ingrowth of bone tissue and building the required bone bridge between the vertebral bodies.
“This performance cannot be attained by simply converting an existing design made for PEEK into a 3D-printed one in titanium, which most manufacturers nowadays do; these designs are a lot stiffer than their PEEK alternatives. It is therefore essential to redesign the entire implant to achieve the desired elasticity. A stiff cage can be very risky for the patient, as it can become unseated and penetrate the vertebrae, causing loss of stability of the vertebral segment. Also, subsidence of the implant that causes deterioration of the bone tissue around the implant is an undesirable and high-risk consequence for the patient,” added Caselli.
Interbody fusion cages
This second generation of additively manufactured solutions builds on years of research and dedication by the team. The company’s second generation of 3D-printed solutions is an addition to the first generation of fusion solutions: a line of interbody cages based on successfully proven Bone InGrowth Technology with options for all surgical approaches.
“With four cages featuring built-in additional fixation features, four expandable ones and the first 3D-printed screw-and-rod system in the world, both for open and MIS procedures, we now are offering a full product portfolio for spinal fusion,” said Caselli.
The cages with built-in fixation differentiate from alternatives by using fixation pins instead of screws. Using screws would require substantially more material to fix the screws, whereas by using pins, the elasticity of the implant doesn’t need to be compromised. The expandable series of interbody cages comes fully assembled from the metal 3D printer. They can be extended three-dimensionally; individual adjustment of height and lordosis angle can be achieved with just one instrument.
Pedicle screw-and-rod system Ventotene
Tsunami has extended its use of additive manufacturing to pedicle screws, now offering a range of fully 3D-printed and CE marked solutions.
The characteristic threading built around a trabecular honeycomb structure is beyond the construction possibilities of conventional manufacturing, while the cannulated and perforated shape, achievable only with additive manufacturing, yields the necessary strength.
Tsunami’s Ventotene system of pedicle screws and bars was recently awarded the CE Mark. To obtain this certification, the systems must exhibit great strength and resistance over time. One of the most rigorous tests that pedicle screws must sustain requires that the screws, attached to nylon phantoms, be subjected to a 180 N strength for five million cycles. The Ventotene screws have been shown to withstand up to 10 million cycles.
Tsunami’s Ventotene additively manufactured screws exhibit up to 20% higher biocompatibility and mechanical properties when compared to conventionally machined products. Their trabecular structure provides a better bonding on the bone and allows, when necessary, the addition of cement from within the cannulated screw.
Since the screws are not made from solid material, they minimize the use of titanium and present a lower radiological footprint, improving the surgeon’s visibility of the surrounding bone tissue.
The Ventotene screw system is currently undergoing ASTM testing for the U.S. market. The tests are like those required for CE marking in Europe. As for the cages, using titanium alloy in the additive process delivers appropriate levels of micro-elasticity needed to build a “bone bridge” to reinforce the vertebral structure.
Given most Tsunami Medical’s customers are based outside of Italy, the work on international standards and certification is linked to the company’s global growth trajectory. In addition to this work, the company is in the process of signing additional distribution agreements for specific geographical areas.
Offering interbody fusion solutions with unique cages for each surgical approach during the last 10 years by itself can be considered a wave of innovation. However, focusing on innovation and differentiation, Caselli and team continuously look for needs in individual and broader international markets and investigate additive manufacturing solutions, for which the company may be considered a turn-key specialist. Recently, Tsunami received the regulatory approval (CE Mark) to bring next-generation interbody fusion cages and a screw and rod system to market, following the successfully proven first generation of additively manufactured surgical solutions for spinal fusion.