Knee osteoarthritis treatment is getting personal.
 
University of Bath (U.K.) researchers have devised a knee realignment system using customized high-tibial osteotomy (HTO) plates made from 3D printed titanium. The plates fit almost perfectly when implanted, thanks to an improved surgical technique also developed by university engineers.
 
“Knee osteoarthritis is a major health, social, and economic issue, and does not receive as much attention as it should,” said Professor Richie Gill, of the university’s Centre for Therapeutic Innovation. “A quarter of women over 45 have it, and about 15 percent of men, so it’s a significant burden that many live with. Knee replacement is only useful for end-stage osteoarthritis, so you can be in pain and have to live with a disability for a long time, potentially decades, before it’s possible. We hope the new TOKA process we’ve developed will change that.”
 
Tailored Osteotomy for Knee Alignment (TOKA) aims to improve HTO plate fit and cut OR time four-fold (from two hours to 30 minutes). The procedure uses a 3D CT (computed tomography) scan to create a customized HTO plate and surgical guide that fit the patient’s shin bone as perfectly as a jigsaw puzzle piece. The HTO plates have already been tested in a virtual in-silico trial, and data from the 28 participants convinced U.K. regulators to greenlight a study in Britain. Hospitals in Bath, Bristol, Cardiff, and Exeter are expected to participate in the randomized controlled study to compare patient outcomes with an existing generic HTO procedure.
 
The TOKA technique also is undergoing testing in Italy, where 25 patients have received customized HTO plates in a trial conducted at the Rizzoli Institute in Bologna.
 
“The HTO surgery has a long clinical history and it has very good results if done accurately. The difficulty surgeons have is achieving high accuracy, which is why we have created the TOKA method, which starts with a CT scan and digital plan,” Gill said. “3D print the custom knee implant and doing the scanning before operating means surgeons will know exactly what they’ll see before operating and where the implant will go. In addition to a surgeon being able to precisely plan an operation, a surgical guide (or jig) and a plate implant, each personalized to the patient, can be 3D printed automatically based on the scanning data. Importantly, this type of treatment relieves the symptoms of knee osteoarthritis while preserving the natural joint.”
 
Natural joint preservation and better implant fit are just two of the many advantages of fabricating implants via 3D printing (a.k.a., additive manufacturing). The technology has expanded rapidly in the orthopedic sector in the past decade because it can create more natural anatomical shapes and porous bone replacement scaffolds that allow for natural bone ingrowth, thus ensuring better implant stability.
 
ODT’s feature “Printer Friendly” explores the ways in which 3D printing is improving orthopedic implant design and patient outcomes. Erik Poulsen, medical market segment manager for GF Machining Solutions Management S.A., was among the half-dozen industry experts interviewed for the story. His full input is provided in the following Q&A. 

Michael Barbella: Please discuss the additive manufacturing/3D printing trends currently driving and shaping the orthopedic industry. Have these trends changed of late?
Erik Poulsen: Our impressions is that the increased availability of the technology is helping to create additional demand; a positive feedback loop that is making it more commonplace to find additive [manufacturing] being used—especially for customized implants. In addition, printing speeds are increasing while the cost of raw materials is dropping, making the entire process more cost efficient.  
 
Barbella: What benefits does additive manufacturing bring to the orthopedic industry?
Poulsen: Product performance and cost are the big benefits that both patients and manufacturers are seeing. Clearly device designs that are more friendly to the body—that are mechanically more like natural bone—is a huge plus. And certain product designs are much more economical when made with additive [manufacturing]. It is also worth mentioning that lead times for custom additive manufactured products are often shorter than from conventional manufacturing—a further benefit to patients.
 
Barbella: What challenges are preventing wider scale adoption of additive manufacturing/3D printing in the orthopedic industry?
Poulsen: Integration of additive into a complete manufacturing chain—seamlessly—remains elusive for many organizations. Many manufacturers are trying to automate their operations, however, they have not always found the answers for downstream machining and removal from the build plate for products where additive is the first step. They end up relying on manual processes far more than they would like to. The designing for additive [manufacturing] is also challenging and implies a mindset change from traditional set up. In addition, there is a limitation on having reliable data for mechanical properties (mainly fatigue), especially versus forged parts, that still prevent additive [manufacturing] from being used in certain applications.
 
Barbella: How has additive manufacturing technology impacted/changed orthopedic implant innovation?
Poulsen: Again, patient-specific solutions and customized implants are possible today not just in theory, but economically. Slowly, we are also starting to see more and more serial implants with innovative designs which are only possible to manufacture via additive.  
 
Barbella: What changes to additive manufacturing technology are spurring innovation in orthopedic implants?
Poulsen: The increased productivity of additive machines as well as a wide choice of materials at reduced costs are lowering the entry barriers, which in turn, drives innovation forward, not only in medical but in many other applications.
 
Barbella: How has software enhanced or impacted the design of 3D printed orthopedic implants?
Poulsen: Clearly certain software packages have improved the ability to convert customer specific CT [computed tomography] scan data into specific CAD—upon which an implant can be modelled with greater precision, and to create new optimized designs including integrated lattice structures. This is certainly the case with 3DXpert, and it has helped open the door for better, more accurate product designs as well as lowering costs by reducing scrap rates. When you include an integrated approach on the CAM side from additive to subtractive technologies seamlessly, the end result is more accurate products.
 
Barbella: What challenges and/or opportunities are associated with using materials other than titanium for 3D printed orthopedic devices/implants?
Poulsen: One of the challenges with materials other than titanium is economic—to be cost competitive, you want to keep your printers running 24-7. When you are printing in two materials you would generally have systems that are dedicated to each material being run. It is sometimes difficult to have sufficient volume in both. On the opportunities side, to be able to print materials with better osseo-integration capabilities and/or performance than Ti are starting to open up and we should expect more coming up in the near future. 
 
Barbella: Where do you see 3D printing in orthopedics headed in the next decade?
Poulsen: We believe that the market will continue to shift towards additive as a major part of any manufacturing operation. We believe customized implants will be (nearly) totally produced by additive [manufacturing] and a significant part of serial implant production would also move to additive, certainly for complex designs.