Despite a few drawbacks, 3-D printing has some promising clinical applications

When 3-D printers were first developed about 30 years ago, the technology had limited capabilities and were large and cost prohibitive. Now that the technology has shrunk both in size and its cost, 3-D printing is more usable across a broad range of fields, including medicine. More orthopaedic surgeons are harnessing the power of 3-D printing to improve their knowledge of anatomy and pathology and, ultimately, to achieve more consistent surgical results.

Orthopaedics Today Europe spoke to some experts in this area about current and future clinical trends in and applications for 3-D printing, as well as the lingering ethical and regulatory questions surrounding this technology. It is clear that 3-D printing is changing the practice of orthopaedics in some ways, according to sources for this article.

“Overall, 3-D printing allows you to visualize and, in some cases, practice surgical procedures for patients who have complex deformities or injuries in a way that we could not do before,” Jason L. Koh, MD, of NorthShore University HealthSystem, in Evanston, Ill., USA, said. “It is transformative in the sense that basically, our imaging was always in two dimensions, and now we can have real 3-D models that we can hold and manipulate. That allows us to have something that, in many cases, is probably closer to the reality of what we have to do in treating the patient.”

Also known as additive manufacturing, 3-printing has been around since the 1980s. The process involves creating a 3-D, solid object from a digital model. The digital model is usually created using a computer-aided design program. In orthopaedics, that requires data from MRI or CT scans. Once the digital model is complete, it is sliced into thin cross-sections that are layered one after another until the object is completed.

Although many materials can be used in a 3-D printer, some common materials used in orthopaedics are sintered powdered metal, stainless steel, nitinol, titanium and ceramic, according to information from the American Society of Mechanical Engineers.

Current applications in orthopaedics

There are several current applications of 3-D printing in orthopaedics. The technology, for example, is used to print custom cutting guides that may help improve surgical planning and accuracy.

“Patients then effectively get a premium product because they are getting technology applied to their case that allows the surgeons to achieve their plan with greater accuracy than would otherwise be possible,” Justin P. Cobb, MD, of the Imperial College London, in London, told Orthopaedics Today Europe.

With 3-D planning, the surgeon knows how to position and orient the components before entering the OR, according to Cobb. This type of planning also ensures the implant is the proper size so there are no surprises in the OR, he noted.

“I personally 3-D plan every single joint replacement that I do as sort of a quality statement,” Cobb said. Globally, however, fewer than 10% of all total joint operations are planned this way, he added.

There are many opportunities for 3-D printing to improve the outcomes of total knee replacement, according to Cobb.

“More people are having MRIs of their knee, for instance, which potentially will show how the damage is localized,” he said. “The MRI not only gives information for 3-D printing of the guides to perform the surgery, but also is objective evidence preoperatively that a total knee replacement is needed.”

The technology is helpful for surgeons when they encounter uncommon orthopaedic problems.

“Personally, I have used it on occasions for patients with trochlear dysplasia,” Koh told Orthopaedics Today Europe. “This is a procedure that you cannot replicate on most normal patients [or] practice on your regular Sawbones or cadaveric specimens because of the fact that the deformity is so unusual.”

Three-dimensional printing has demonstrated its utility in the hip as well, according to Koh. Surgeons at his institution have used this technology for complex revision total hip replacement, in which the acetabulum is damaged.

“[3-D printing] allows us to go into a complex procedure with a unique anatomy being confident and comfortable,” Koh said. “It is so much easier to sort of figure out exactly where we are making cuts or placing hardware, rather than trying to do that for the first time when actually looking at it.”

In addition, he said 3-D printing accelerates component placement.

“There are some data showing it speeds the ability to place the component accurately,” Koh said. “It is useful for fracture cases where you know you have multiple fragments that you are trying to figure out.”

Spine cage production

Based on presentations at recent meeting and the literature, this technology is well-suited for spine applications.

“At the moment, I used 3-D-printed implants for cages for the disc space in terms of fusion and spondylolisthesis,” Ralf Wagner, MD, of Ligamenta Spine Center, in Frankfurt, Germany, said.

He recently began using the 3-D printed EndoLIF implant (Joimax), which is a titanium implant created using Electron Beam Melting (EBM) technology.

“It is a titanium alloy,” Wagner told Orthopaedics Today Europe. “The advantage is you have a good surface of titanium, which allows you to have a good in-growth without having a lot of bone substitute or bone material.”

The preliminary results with this approach after 1.5 years indicate there is good bone in-growth, without the need to use a bone substitute, and high primary stability, according to Wagner.

“I was afraid in the beginning there would be some kind of stability problem compared to a single piece of metal, but at the moment, I have not seen any breakages or any problems with that,” he said.

Complex spine deformity, fracture treatment

Three-dimensional printing is also used in complex spinal deformity cases, especially when severe curves occur not just in the sagittal or coronal planes, but also in the rotational plane, according to Koh. The literature shows 3-D printing helps some orthopaedic surgeons and traumatologists with fracture repair. Italian researchers used 3-D printed models of distal radius and scaphoid fractures to better understand the resultant fracture patterns. They were able to learn more about the lesions, as well as better plan their surgical repair, with the help of 3-D printing.

In their study, Shuang and colleagues demonstrated 3-D printed osteosynthesis plates were safe and effective in the treatment of intercondylar humeral fractures. They also noted there was a significantly shorter operative time when they used these plates.

Downsides to 3-D printing

While 3-D printing offers many opportunities, there are some drawbacks. The printers are slow, for instance, building at a rate of cubic millimeters per minute, according to Brian Derby, FIMMM, a professor at the University of Manchester, in Manchester, United Kingdom.

“Typically, using current technology, if you wanted to make something the size of a golf ball, you would be talking about some hours to make it,” Derby said. “You can print material like bone, you can print something like a blood vessel, but each of those objects [multiplies] up the time of making it.”

Printing 3-D, living tissue or body parts is complex, according to Derby.

“If you are going to print something the size of an organ or a piece to go into an organ, you have to put a billion cells into it,” he said. “If you are trying to precisely make something, with all the cells in the right place, you have got to make a billion positioning decisions.”

Furthermore, to use the technology requires a certain degree of technical expertise.

“[It requires] a certain amount of technical proficiency in order to take the data and then essentially subtract out the things you do not want,” Koh said. “Northshore University Health System has an informatics group, and so they are able to do that kind of processing for us, [and] a number of implant manufacturers do that kind of processing routinely for some of these customized joint replacements.”

There are also regulatory issues with regard to 3-D printing that sources who spoke with Orthopaedics Today Europe mentioned.

“The way [U.S. Food and Drug Administration] FDA and the other regulatory bodies approve things is they want to know that whatever it is you are making is exactly the same every time you make it,” Derby said. “If you are making something which is different every time you make it; how do you define whether that sign of quality ought to be used? [One] will have to rethink how one approves these things.”

Future applications may reduce costs

As this technology evolves and more people use it, the role of 3-D printing medicine is expected to expand.

“It is going to be the path of the future because it is going to improve the reliability and reduce the cost,” Cobb said. “I think every company is going to use it because it will be the only way that they can deliver the quality and the price.”

At some point, this technology may be used to make custom-made implants.

“I think the promise of this technology is maybe you can get implants that are really customized to fit each patient,” Koh said. “Right now, we have custom guides to fit the patients and there are some patient-matched implant companies, but there is the possibility that this could be much more common.”

For this to happen, the informatics must be sophisticated, Koh said. However, 3-D printing still may not produce the once-promised revolution.

“I think you could see how it could revolutionize in certain areas, but I think revolutions rarely happen in medicine,” Derby said. “When penicillin was introduced [it] took 30 years from Fleming [discovering it] to the drug companies producing it. These things take time.” – by Colleen Owens

• References:
• Bizzotto N, et al. Injury. 2016.doi:10.1016/j.injury.2016.01.013.
• Miller JS. PLoS Biol. 2014.doi:10.1371/journal.pbio.1001882.
• Shuang F, et al. Medicine (Baltimore). 2016.doi:10.1097/MD.0000000000002461.
• www.asme.org/engineering-topics/articles/manufacturing-processing/top-10-materials-3d-printing
• www.pcmag.com/encyclopedia/term/37077/3d-printing

• For more information:
• Justin P. Cobb, MD, can be reached at Imperial College of London, Room 7L25, Floor 7, Laboratory Block, St. Dunstan’s Rd., Charing Cross Campus, London, W6 8RP, United Kingdom; email: j.cobb@imperial.ac.uk.
• Brian Derby, FIMMM, can be reached at School of Materials, University of Manchester, Oxford Rd., Manchester M13 9PL, United Kingdom; email: brian.derby@manchester.ac.uk.
• Jason L. Koh, MD, can be reached at Northshore University Health System, 1000 Central Station #880, Evanston, IL 60201 USA; email: drjasonkoh@gmail.com.
• Ralf Wagner, MD, can be reached at Ligamenta Wagner & Sabljic, Wirbelsäulenzentrum GbR, Walter-Kolb-Str. 9-11, 60594 Frankfurt am Main, Germany; email: ralf.wagner@ligamenta.de.

Disclosures: Cobb reports he is co-founder of Embody, which specializes in 3-D customization and planning. Derby, Koh and Wagner report no relevant financial disclosures.

 

Is 3-D printing in orthopaedics the way of the future or is it mainly experimental technology?

Technology offers innovative solutions to old problems

We are all unique. Although we share similarities in our makeup, rarely does a surgeon come across an identical anatomy or a physician see the same response to a certain medication. Three-dimensional printing is a tool that recognizes this and can bring individualized solutions that benefit both patients and doctors.

It is being used to provide customized composite materials, which can be optimized for their specific use. Biological activity, mechanical strength and dimensions are just a few of the variables that can change for each device made. The printing process itself offers many advantages to traditional manufacturing, particularly in cost and timing.

It is helping surgeons who work in difficult situations to plan their surgery with custom jigs designed off 3-D scans, improving both outcomes and safety.

In a world of nanotechnology, biological composite materials and personalized health care, it is a technology that is in its infancy, but will continue to offer innovative solutions to some old clinical problems, embracing the fact that each situation is different.

Jasvinder S. Daurka, MBChB, is a consultant orthopaedic surgeon at the Imperial College Healthcare NHS trust and is an honorary senior lecturer at the Imperial College London.
Disclosure: Daurka reports no relevant financial disclosures.

More than just an experimental technology

Three-dimensional printing, also known as additive manufacturing, has received increasing interest from the health care sector during the past several years. This is especially true in orthopaedics, where 3-D-printed patient-specific implants are found helpful in certain cases of tumor, trauma, deformity, etc., which involve difficult reconstruction, by providing patients with an individualized solution to their unique circumstances. These niche market conditions represent huge needs that are unmet by products from mass market medical device companies. In addition, compared with conventional techniques, 3-D printing has enabled manufacturing of more desirable ultra-structures that may potentially facilitate osteoinduction and drug delivery. This may be of particular interest to manufacturers from developing countries as 3-D printing can help them achieve the level of precision beyond their previous technical capabilities.

Three-dimensional printing can be applied to other areas of orthopaedics, including prostheses, surgical templates and preoperative planning, as well as educational tools for patients and students. As of today, 3-D printing is already more than just an experimental technology for orthopaedic surgeons and we should not be surprised to see it becoming more available in the next few years.

However, this is not to say we are advocating for its routine use in every case. After all, one would ideally like to have a suit to be tailor-made, but the department store suit may fit just as well. Most people can run just fine with any pair of running shoes, but there are occasions where footwear prescriptions are helpful and necessary.

Zhongjun Liu, MD, is a professor of orthopaedics at Peking University and chairman of the Department of Orthopaedic Surgery at Peking University Third Hospital in Beijing.
Disclosure: Liu reports no relevant financial disclosures.

Useful for training

Three-dimensional printing is an interesting new technology that is already widely used in various fields. In orthopaedic surgery, it has been applied to the manufacture of prosthetic components, mostly acetabular cups, starting from a CT scan and then forwarded to the 3-D printer, which converts an image into a 3-D structure. Practically, this is the evolution of the original design and manufacturing digital systems that were used at the end of the 1970s in various laboratories all around the world.

The advantage of this procedure lies in the exact customization of the implant that is adapted to the patient’s bone and not vice versa. This is particularly important in revision surgery, tumors, trauma, congenital hip disease and in any other situation where we have to deal with more or less severe bone stock loss.

Another interesting application of 3-D printers can be the production of a plastic prototype exactly identical to the bone segment (pelvis, knee, etc.) of patients with severe congenital or acquired deformities. In this way, the surgeon has the possibility of performing a trial operation on the plastic prototype, before dealing with the real deformity. Obviously, this is useful also for teaching purposes. Today, 3-D printing has been adopted by several companies to produce their implants and has been shown to represent great progress in industrial technology.

Roberto Binazzi, MD, is chairman of the Department of Hip Surgery at Villa Erbosa Hospital in Bologna, Italy.
Disclosure: Binazzi reports he is a consultant to LIMA and CeramTec.

Change in surgical practice

Orthopaedic surgery requires an excellent 3-D visualization to perform modern bone reconstruction techniques. Obviously, training improves when you can practice on a real bone model. With a domestic 3-D printer, we can easily reproduce a realistic plastic model from patients’ CT images. That model provides the opportunity to plan surgical steps and to choose the best implant and type of reconstruction for that specific case. Furthermore, we could use it to easily design a cutting template to perform a perfect osteotomy for deformity correction. Current 3-D printing technology offers the surgeon multiple options to train in new surgical techniques, reduce surgical time and perhaps improve clinical results.

We should be aware this technology may change our current surgical practice in the coming years. Our challenge, as orthopaedic surgeons, should be to find clinical applications of 3-D printing and work side-by-side with engineers to achieve these objectives as much as possible and progressively reduce real costs and those related to the time it takes to perform a surgery. We will not shy away from this technology, and we should keep informed of developments in this field to improve our clinical results.

Óliver Marín-Peña, MD, practices in the Hip-Knee Orthopedic Department at the University Hospital Infanta Leonor in Madrid.
Disclosure: Marin-Peña has no relevant financial disclosures.