Preoperative planning with 3-D printing may increase efficiency in total joint procedures
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 cost, 3-D printing is more usable across a broad range of fields, including medicine. More orthopedic surgeons are harnessing the power of 3-D printing to improve their knowledge of anatomy and pathology, and to achieve more consistent surgical results.
“Three-dimensional 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, director of NorthShore Orthopaedic Institute, said. “It is transformative in the sense that our imaging was always in 2-D, and now we can have 3-D models that we can hold and manipulate. This 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-D printing has been around since the 1980s. The process involves creating a 3-D, solid object from a digital model, which is often created using a computer-aided design program. In orthopedics, 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 orthopedics are sintered powdered metal, stainless steel, nitinol, titanium and ceramic, according to information from the American Society of Mechanical Engineers.
According to Craig J. Della Valle, MD, professor of orthopedic surgery and chief of the Division of Adult Reconstruction at Rush University Medical Center and Orthopedics Today Editorial Board member, 3-D printing technology can be most applicable during revision surgery, specifically revision total hip arthroplasty, due to the ability to more easily plan for complex total joint cases.
“If you have someone who has a large acetabular defect, sometimes it can be challenging from plain X-rays or a CT scan to understand where there is bone loss and where there is not,” Della Valle said. “The most obvious application, in my mind, is to get a CT scan and then build a model of the pelvis that you can understand and preoperatively plan with the model in your hand to get a preview of what you are going to see in the OR. If the manufacturer can print you an implant that fits the defect well, then that would make it a lot easier than what we are doing today.”
According to Michael J. Yaszemski, MD, of the Orthopedic Surgery Department and the Biomedical Engineering Department at the Mayo Clinic and John Posy Krehbiel endowed professor of orthopedic surgery and biomedical engineering, using 3-D printed materials to practice total joint replacement surgery ahead of the surgery “makes for a safer operation, more realistic expectations by the patient when they can see what the change is going to be and what the surgery makes, and understand the likely outcomes, the potential difficulties [and] the potential problems that can occur.”
“[Three-dimensional printing] allows us to go into a complex procedure with a unique anatomy being confident and comfortable,” Koh said. “It is easier to figure out exactly where we are making cuts or placing hardware, rather than trying to do that for the first time when looking at it.”
In addition, Koh said 3-D printing accelerates component placement.
“There are some data showing [3-D printing] speeds the ability to place the component accurately,” Koh said. “It may be useful for fracture cases, where you know you have multiple fragments that you are trying to figure out. Where we have found it particularly useful is in preparing for complex osteotomies treating fracture malunions or trochlear dysplasia.”
Spine cage production
Based on presentations at a recent meeting and the literature, this technology is well-suited for spine applications. According to David A. Wong, MD, MSc, of Denver Spine Surgeons, Japanese researchers presented a paper on the use of 3-D printing to size post-corpectomy implants for patients during the Eurospine Annual Meeting, which took place in Berlin.
“[Three-dimensional printing] has some application for the custom manufacture of vertebral body prostheses and issues, such as customizing rod bending to optimize deformity correction, etc.; its use is still in the early stages regarding spine and certainly behind development of applications in other surgical arenas, such as total joint,” Wong told Orthopedics Today. “At this point, we have only scratched the surface in exploring potential spine applications of 3-D printing.”
“At the moment, I use 3-D printed implants for cages for the disc space in terms of fusion and spondylolisthesis,” Ralf Wagner, MD, of Ligamenta Spine Center, told Orthopedics Today.
He recently began using the 3-D printed EndoLIF implant (Joimax), which is a titanium implant created using Electron Beam Melting technology.
“It is a titanium alloy,” Wagner said. “The advantage is you have a good surface of titanium, which allows you to have a good ingrowth without having a lot of bone substitute or bone material.”
Images: Koh JL
The preliminary results with this approach after 1.5 years indicate there is good bone ingrowth, 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.
Three-dimensional printing is also used in complex spinal deformity cases, especially when severe curves occur in the sagittal, coronal and rotational planes, according to Koh. The literature shows 3-D printing helps some orthopedic 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. With the help of 3-D printing, they were able to learn more about the lesions, as well as better plan their surgical repair.
In a separate study, Feng Shuang, MD, and his colleagues demonstrated that 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.
Besides using 3-D printing for total joint and spine surgeries, Jane M. Matsumoto, MD, pediatric radiologist at the Mayo Clinic, noted 3-D printing can be beneficial in pre-surgical planning for tumor resection and limb reconstruction, among others. Surgeries may benefit from improved planning and accuracy by 3-D printing custom-cutting guides.
“On one side we have surgical planning, [which] includes planning for osteotomies or custom-cut guides for different procedures, like knee replacements and hip replacements,” Jonathan Vigdorchik, MD, assistant professor of orthopedic surgery and co-director of robotics at NYU Langone Medical Center, told Orthopedics Today.
Three-dimensional printing can also not only be used for education and training of residents and fellows, but also for patient education by using it as a visual example of what the patient’s medical problem is and how treatment will be addressed, according to Yaszemski.
“[Three-dimensional printing is] used in orthopedics for education and training for residents and fellows. We can make 3-D models of parts that will be operated on, and we can practice the operation on those models,” Yaszemski said.
Matsumoto also noted 3-D printed models have been found to be educational for all members of the OR team.
“Much of surgery today is done laparoscopically, and many of the OR support staff are not able to visualize what is happening during surgery. The models help them understand the anatomy, goals and complexities of an individual’s surgery. We have found the educational contribution of the models to be significant at all levels of learners,” Matsumoto said.
Three-dimensional printing can be cost effective by limiting the amount of trays needed in the OR, Vigdorchik noted.
“[Three-dimensional printed material is] disposable. It limits the amount of trays we need in the OR, so it could make the procedures go more efficiently and faster,” Vigdorchik said.
However, Vigdorchik added there is still room for improvement when it comes to 3-D printing. Custom 3-D printed implants can be costly, take companies 4 weeks to 6 weeks to produce and may not improve patient outcomes.
“We are finding better ways to improve our accuracy to [perform] different joint replacements, and in the past, 3-D printed custom guides have been good at helping efficiency, but they are a little bit costlier and [did] not seem to change the outcomes. We need to improve planning and creation of things to help make it better,” he said.
Vigdorchik recommends for patients to undergo a CT scan to produce a custom implant, which exposes patients to radiation. Yaszemski recommends surgeons move methodically and make sure 3-D printing is safe for each patient.
“[It requires] a certain amount of technical proficiency in order to take the data and then subtract out the things you do not want,” Koh said. “NorthShore University HealthSystem has an informatics group, and they are able to do that kind of processing for us. A number of implant manufacturers do that kind of processing routinely for some of these customized joint replacements.”
Despite current high costs, Vigdorchik said by discovering how to create large scale, inexpensive, fast 3-D printed implants, surgeons will be able to improve quality and efficiency, which will help drive down costs.
“Where [3-D implants are] right now, it is relatively expensive to print, [but] the costs are heading south where it starts to make more sense,” Della Valle said. “It seems to be a technology that is changing extremely rapidly so for preoperative templating, it could lead to reductions in OR time, in surgeons doing a better job [because] they know exactly what they are going to see at the time of surgery, and they would be more efficient and that could lead to cost savings.”
As the cost continues to decline, companies will be able to eventually produce custom-made implants for patients, but the informatics must be sophisticated, according to Koh.
“The promise of this technology is maybe you can get implants that are 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 more common.”
While surgeons have the tools to preoperative plan complex surgeries for a more precise and reproducible intraoperative procedure, Vigdorchik noted 3-D printing is coming, but more research is needed.
“Three-dimensional printing is coming, and it is going to be here to stay, but do not jump on the bandwagon until we get some established clinical data,” Vigdorchik said. “Where we get into trouble is when we have a lot of early adopters and then an implant fails and [is recalled]. We have to stay true to our research methods and make sure that we study all new implants and new technology thoroughly, so we can get that clinical track record to make sure that it is safe for our patients.” – by Colleen Owens and Casey Tingle
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- For more information:
- Craig J. Della Valle, MD, can be reached at 1611 W. Harrison St., Suite 400, Chicago, IL 60612; email: firstname.lastname@example.org.
- Jason L. Koh, MD, can be reached at NorthShore Orthopaedic Institute, 2650 Ridge Road, Walgreen’s Building, Suite 2505, Evanston, IL 60201; email: email@example.com.
- Jane M. Matsumoto, MD, can be reached at the Mayo Clinic, 200 1st St. SW., Rochester, MN 55902; email: firstname.lastname@example.org.
- Jonathan Vigdorchik, MD, can be reached at NYU Langone Preston Robert Tisch Center for Men’s Health, 555 Madison Ave., 2nd Fl., New York, NY 10022; email: email@example.com.
- Ralf Wagner, MD, can be reached at Ligamenta Wagner & Sabljic, Wirbelsäulenzentrum GbR, Walter-Kolb-Str. 9-11, 60594 Frankfurt am Main, Germany; email: firstname.lastname@example.org.
- David A. Wong, MD, MSc, can be reached at Denver Spine Surgeons, 7800 E. Orchard Rd., Ste. 100, Greenwood Village, CO 80111; email: email@example.com.
- Michael J. Yaszemski, MD, PhD, can be reached at the Mayo Clinic, 200 1st St. SW., Rochester, MN 55902; email: firstname.lastname@example.org.
Disclosures: Della Valle reports he receives support from Smith & Nephew.Yaszemski reports he has intellectual property on 3-D printed items and is a consultant for Medtronic and K2M. Koh, Matsumoto, Vigdorchik and Wagner report no relevant financial disclosures. Wong reports he is a consultant for UnitedHealthcare.
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