Additive Manufacturing Thrives With Fresh Ideas

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. Peter Halverson, principle engineer at Draper, Utah-based Nexus Spine, was among the half-dozen industry experts interviewed for the story. His full input is provided in the following Q&A.
 
Michael Barbella: What benefits does additive manufacturing bring to the orthopedic industry?
Peter Halverson: Additive manufacturing (AM) has allowed for the creation of designs that were not previously possible. With past techniques, we were limited to geometries that we could reach with physical tooling. With additive manufacturing, we can create structures and features internal to the part. These features can increase the function and performance of the part without a proportional increase in production costs. Additionally, additively manufactured titanium has been shown to be very bone-friendly producing the reactions necessary to facilitate boney attachment and ingrowth.

Barbella: What challenges are preventing wider-scale adoption of additive manufacturing/3D printing in the orthopedic industry?
Halverson: There is a lot of experience in the industry as it relates to more traditional manufacturing processes. When old designs are manufactured using AM, they often result in products that are much more costly. Instead, new designs are needed to take advantage of the unique aspects of AM.

Barbella: What is different about the 3D printing technology/process Nexus Spine uses to produce its spinal implants? How does the finished product differ from other 3D-printed spinal implants?
Halverson: Nexus has been able to capitalize on the ability to produce a large number of flexible mechanisms internal to the implant. This has allowed us to decrease the stiffness of our interbody spacers to match that of vertebral bone. A bone-matching stiffness should accelerate boney formation and attachment and decrease pain and healing times. Competing produces simply cannot match that stiffness.

Barbella: What challenges and/or opportunities are associated with using materials other than titanium for 3D printed orthopedic devices/implants?
Halverson: Corrosion in additively manufactured stainless steel parts can be a concern. Plastics manufactured used AM often exhibit weaker mechanical properties in some directions than others. As a result, care must be taken in the orientation of the parts during fabrication.

Barbella: Where do you see 3D printing in orthopedics headed in the next decade?
Halverson: As AM becomes more widespread, its use will advance to patient-specific implants that are designed to match the individual’s physiology and desired clinical outcome. This patient-specific approach will be especially relevant in pediatrics.