For orthopedic implant manufacturers, find a faster and easier way to generate and modify lattice design software with high design volumes to speed up design, build strategies and ensure 3D printing process Reliability of the 3D printing process is key to success.
In this issue, 3D Science Valley and its friends will learn more about how Italian surgeons use Siemens NX AM at the implant manufacturer Lima to reduce design iterations, reduce errors and improve reliability.
3D printed orthopedic implants
© Lima
According to 3D Science Valley, 3D printing - Additive manufacturing can adjust the local density according to load and other requirements with the help of different material distributions. Furthermore, with customized digital materials, component weight, cost and production time can be optimized. Additive manufacturing (AM) is a breakthrough production technology that enables the efficient production of digital materials due to its geometric freedom and tool-free production.
3D printed implants
© 3D Science Valley White Paper
Better implants lead to better quality of life
Italian surgeons at implant manufacturer Lima is a global orthopedics company focused on digital innovation and custom orthopedic implants into things to advance patient-centered care. Its product range includes joint implants, limb immobilization solutions and specialized patient-specific prostheses. The latest developments for
Lima come from a collaboration with Siemens to improve the design and manufacturing process for 3D printing, reducing AM- additive manufacturing modeling and job preparation time by 50%.
Lima has been using 3D printed “cementless” implants for a long time. According to market observations from 3D Science Valley, it all started in 2005. At that time, almost no company considered using 3D printed for mass production. Lima is headquartered in Global orthopedic developers in Italy were also just beginning to use 3D printing technology for rapid prototyping. At that time, it was not even possible to 3D print using the titanium alloy material required for implants, and the scrap rate at the time was high, about half of the scrap rate. Despite this, Lima is still determined to pursue the industrialization of 3D printing-additive manufacturing technology.
To this day, from the initial purchase of EBM 3D printing equipment for the development of acetabular cup implant product prototypes, to the launch of the first mature 3D printed acetabular cup implant Lima Delta TT Cup in 2007, to the current use of TT Technology manufactures various types of orthopedic product portfolios from hips to limbs, as well as providing customized implant solutions for patients with specific needs. Lima's ten years of persistence has not only helped doctors solve many clinical problems, It has also contributed to promoting the application of 3D printing technology in the field of orthopedic implant manufacturing.
A major trend in the development of orthopedic implants is the use of lattice lattice structures in joint replacement . These lightweight metal structures improve osseointegration—the connection between the implant surface and living bone. Before the industry began developing lattice-based metals—and even today—the gold standard for arthroplasty was to immobilize the joint with cement. In this case, bone ingrowth is achieved by diffusion bonding of the plasma sprayed coating. This approach results in low friction, low porosity , and limited osseointegration.
Using 3D printed metal implants with a lattice structure, the intuitive benefit of this cementless arthroplasty is that bone ingrowth will strengthen over time.
According to 3D Science Valley, based on the objective function, the distribution of pore characteristics in AM additively manufactured porous structures can be uniform or non-uniform. Uniform scaffolds have unit cells of specific shapes and porosity, whereas non-uniform (gradient) scaffolds include arrays of unit cells in which the pore characteristics spatially vary in the design space to achieve one or more functions in the scaffold.
Lima is not the only company to see the value of lattice structures for implants. Its rivals have even acquired a company developing tantalum-based porous metals. The technology requires tantalum to be deposited on a polymer material and then bonded to the solid material using diffusion bonding techniques.
Lima envisions combining porous titanium and solid titanium in one step via 3D printing, without the need for coatings. To achieve this goal, Lima invented Trabecular Titanium™ (TT) in 2007. 3D Science Valley mentioned in the article "Ten years of hard work, Italian orthopedic medical device company Lima insists on creating 3D printed implant products" that Trabecular Titanium technology is a technology that uses metal 3D printing equipment to manufacture titanium orthopedic implants. , The surface of 3D printed implants has a porous structure. The difference from the surface coating made by plasma spraying and other processes is that this structure is a bionic structure directly manufactured by 3D printing equipment, and the geometric structure of the holes can be accurately determined. Control, for example, the acetabular cup implant manufactured with Trabecular Titanium technology has a porosity of 65% and an average pore diameter of 640 μm. The porous implant structure created by metal 3D printing technology can promote bone ingrowth, resulting in better recovery results.
Lima manufactured the acetabular cup using Trabecular Titanium technology. At that time, there was no international standard for 3D printed parts, and convincing the authorities to accept the products manufactured by Lima was full of challenges. A full set of data for verification, testing and quality assurance had to be provided.
Eventually, regulators gave the go-ahead—which led to even greater challenges. After Lima was certified, demand was so high that it was immediately out of stock. The state of metal additive manufacturing was unproven at the time, and the scrap rate for 3D printing was so high that Lima had to keep ordering more 3D printing-additive manufacturing machines to fulfill orders, and validating each machine took time.
According to 3D Science Valley, currently, even for personalized customized 3D printed implants that do not have the opportunity to conduct clinical trials for many years, scientific and rigorous biomechanical evaluation and analysis can be carried out in the implant design stage to 3D Strict monitoring of printing processes and materials, as well as later quality inspection and other processes, ensure the safety of implants.
Since the introduction of acetabular cups made with Trabecular Titanium technology in 2007, Lima has produced more than 100,000 acetabular cups with excellent clinical results. A 2015 study found that at least five years after surgery, patients' average Harris hip score improved from 44.2 to 95.9 on a 100-point scale. Most recently, the cup received an Orthopedic Data Evaluation Panel (ODEP) 10A rating, the highest rating for survival at 10 years of follow-up. The success of the
acetabular cup convinced Lima that Trabecular Titanium technology could be used to 3D print other implants. But as more competitors compete in the market to take advantage of cementless joint replacements, Lima needs to improve the speed and efficiency of its additive manufacturing workflow.
Key collaboration drives innovative knee replacement
When Lima decided to have a cementless total knee arthroplasty (TKA), the challenges were even more difficult than those faced by an acetabular cup. 3D Science Valley understands that hip replacement surgery is simpler than knee replacement surgery. The hip joint is a ball and socket joint, while the knee joint is a complex joint that allows for a wider range of motion. The
knee implant contains three components: the femoral component connects to the lower thigh bone, the tibial plate connects to the upper tibia, and the polyethylene insert sits in between. The femoral component is produced from solid metal through precision machining.
To better understand how the motion of walking transfers force to the tibial plate, Lima collaborated with the Department of Biomechanics at the Hospital for Special Surgery (HSS) in New York. The team studied patients walking with knee implants to determine the The optimal position and shape of the three contact points between plate and bone.
The team also evaluated bone density in implant patients in the United States and Italy. From these two studies, HSS Hospital performed a computer stress analysis of the contact point configuration to arrive at a design that included two porous TT pegs, a porous front peg with a solid tip, and a porous surface underneath the plate. It went through many design iterations, including the number, location, shape, depth, etc. of pegs.
This high degree of iteration exposed areas where Lima’s additive manufacturing process needed improvement. For each change in 3D printing, an STL file must be created and put into a different software package.Then, if there is another change, the subsequent conversion of the corresponding STL file will be very difficult.
uses a digital representation of the lattice structure to make the design more complex. Trying to edit the lattice structure from an STL file consumes a lot of computing resources, so Lima needed a faster and easier way to generate and modify designs with high Quantitative lattice structure.
Furthermore, Lima’s challenges were not limited to the time delays associated with processing complex 3D printing files. For example, when an STL file is manipulated within an isolated software tool, the software tool introduces "digital discontinuity."
Lima needed a new approach to designing its tibial plates, requiring an integrated, associative digital thread throughout the design and manufacturing process. In this regard, Siemens NX and Teamcenter are part of the Xcelerator portfolio, a comprehensive, integrated portfolio of software and services offered by Siemens Digital Industry Software.
Solving the "digital discontinuity" of lattice designs
Lima evaluated NX AM in 2018. Shortly thereafter, Lima became a Siemens NX AM beta testing partner, reducing reliance on STL files through NX AM, using lattice Performing lattice designs becomes easier and is seamlessly integrated within Lima’s Teamcenter environment.
© Siemens
The use of NX AM brought immediate benefits to the development of tibial plates. Designers no longer need to worry about processing STL files and can parametrically edit most features of the tibial plate because they are mathematically related to the geometry .
's use of NX AM also simplifies the task of designing Lima lattice structures. Taking into account all the properties of the proprietary lattice structure, custom-designed unit cells, with NX AM, Lima reduced the computational time of designing trabecular titanium structures. And because it's almost completely parametric, design changes update automatically.
In Lima's old process, modifying STL files was disconnected from the workflow, thus increasing the risk of human error. 3D Science Valley learned that by having everything in a single digital stream and one-click lattice design, the entire process was made more efficient. .
© Siemens
Now, Lima is not only developing a tibial plate but also producing it in 10 off-the-shelf sizes. This is of great significance for 3D printing to move towards mass production. Lima currently comes in a range of sizes optimized for the global market, for small to large patients and for people with different needs, each requiring adjustments to the characteristics of the tibial plate.
reduces 3D printing-additive manufacturing modeling and job preparation time by 50% with NX AM. Through design optimization, Lima can achieve better designs with less experimentation, reducing errors and increasing reliability through the Siemens software ecosystem.
3D printing also helps manufacturers get closer to patients, and Lima currently has an additive manufacturing facility installed at HSS Hospital, where Lima’s production engineers use Siemens software to help surgeons develop patient-specific implants.
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