Surgeons push barriers with 3D printing for bone tumors
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Despite the long-established prevalence of 3D printing in orthopedic oncology, some orthopedic surgeons said recent technological improvements and novel applications of the tool may help change the way cancerous tumors are treated.
In an interview with Healio | Orthopedics Today, Peter S. Rose, MD, FAAOS, professor of orthopedic surgery at the Mayo Clinic, said 3D printing “holds the promise to give better outcomes for our patients.”
Source: Mayo Clinic
“This is an exciting area of orthopedic surgery,” he added. “As the technology develops and becomes more refined, we are going to understand its place in current clinical care.”
According to Joel L. Mayerson, MD, FAAOS, FAOA, director of the sarcoma program at The James and chief of musculoskeletal oncology at The Ohio State University, “[3D printing] is going to give us the best opportunity we have ever had to be able to precisely fit these implants to allow them to hopefully osseointegrate into the bone that is remaining and to create a stable, long-lasting construct with decreased surgical time and precision to give it the best outcome.”
Reconstruction of bone defects
One of the main benefits of 3D printing is the ability to reconstruct bone defects, according to Edward J. Fox, MD, chief of the division of musculoskeletal oncology at the Penn State Health Milton S. Hershey Medical Center.
“[Manufacturing companies] can utilize 3D reconstructed imaging to fabricate a jig to allow us to make cuts in the bone that we would normally have to eyeball,” Fox told Healio | Orthopedics Today.
These cuts are critical when performing a reconstruction with an allograft cadaver bone, according to Fox. He said surgeons need to be able to remove the tumor segment, plug in the cadaver bone segment and reconstruct it to an almost exact fit.
“[3D reconstructed imaging] makes my life easier without having to sweat the details of is this cut right. Is the cut too close to the tumor? Is the cut-off at the wrong angles and now the graft is not going to fit perfectly to allow good bone healing? So, that is another aspect of 3D printing in the engineering world that has come to the table for orthopedic oncology surgery,” Fox said.
Similarly, John A. Abraham, MD, FACS, FAAOS, founder and president of Abraham Orthopaedics and director of the Sarcoma Center of Excellence at Capital Health, said, “the customizability allows us to deal with any bone defect problem that we have in orthopedic oncology.”
He continued, “The reason that is important in oncology is because one never knows what the size or the extent of the tumor is going to be. It is difficult to make an off-the-shelf implant that solves all the problems that we are likely to face. This is the obvious solution: you do not take it off the shelf. You make it for each individual case.”
Joint preservation
Another advantage of custom implants is the ability to preserve joints, according to Herrick J. Siegel, MD, professor of orthopedic surgery at the University of Alabama Birmingham Medical Center.
“If a malignant bone tumor is close to a joint but not actually involving the joint, preoperative planning software allows us to execute a plan that can preserve the joint without sacrificing a sufficient tumor margin. A 3D custom implant can be made to exactly fit the bone defect created by the tumor resection and still preserve a functional joint,” Siegel, who is a Healio | Orthopedics Today Editorial Board Member, said. “I prefer to avoid replacing the joint if we can still maintain a negative margin; this will more likely restore normal biomechanics of the involved extremity.”
Mayerson said utilization of allografts can also assist with the possibility of joint preservation thanks to 3D printing.
“When we are leaving smaller amounts of bone than we historically have in the past, we can get fancier cuts and save people’s joints,” Mayerson said. “Where in the past we would have probably had to do a total joint replacement, we can now save their bone and use an allograft to reconstruct it.”
Preoperative planning
Before an operation begins, 3D printing can give surgeons an advantage in the preoperative phase, according to Rose.
“As we look at resection guides and implants, the corollary to printing a model of the patient with their tumor is printing a guide that will match up and this allows you to plan an operation ahead of time,” Rose said. “It allows you to identify critical structures that you can spare and, in doing so, minimize the impact on the patient while still getting the cancer out safely.”
Moreover, Siegel said the ability to plan a procedure preoperatively and execute it with 3D-printed implants can lead to new possibilities in terms of procedure accuracy and efficiency, which would likely translate to less complications and patient morbidity.
Source: Peter S. Rose, MD, FAAOS
“With computer-assisted preoperative planning, we can locate a specific allograft with identical anatomic features that will exactly fit a defect created by the removal of the tumor,” Siegel told Healio | Orthopedics Today. “It allows us to select a particular allograft that fits appropriately for sizing, and sometimes we can even age match. Implant companies can also design cutting guides to resect the bone around a tumor with precision, which is particularly helpful in pelvic bone resections. So, it not only cuts the tumor out through the custom cutting guide, but we can replicate the cutting guide for preparation of the cadaver allograft on the back table to the same shape as the bone defect.”
Lead time
Despite the various benefits of 3D printing in orthopedic oncology, Abraham said extensive lead times between ordering a 3D-printed tool and when a clinician receives it remains a challenge.
“It is definitely a big concern,” Abraham said. “And it is particularly a concern in oncology because the tumor is not sitting still. If I am waiting 6 weeks or 8 weeks for an implant, then I do not know if the tumor has grown during that time.”
However, compression of the lead time could provide confidence that the tumor would not progress or change, according to Rose, which Fox said could be done through in-house 3D printing.
“One of my visions of the future is for hospitals to bypass the manufacturer and, at least at an academic institution, utilize a team of engineers to be able to work with the physicians and images at hand and in-house 3D custom fabricate a device that will be implanted into the patient, cutting down the fabrication time, cutting down the implant cost as well, potentially, and providing a unique custom solution for the patient’s problem,” Fox said.
Gregory Lewis, PhD, associate professor in the department of orthopedics and rehabilitation at Penn State College of Medicine, said smaller, academic centers may not be equipped to handle various requirements of the manufacturing process.
“Good manufacturing practices and quality control of the manufacturing are things that, as a university, we do not deal with too much, but manufacturers deal with quite a bit,” Lewis told Healio | Orthopedics Today. “So, that piece will also need to be addressed.”
Costs
Cost is another issue when it comes to the use of 3D printing in orthopedic oncology, according to Abraham.
“There is a lot of design work that involves ... a different type of team than we are used to having,” Abraham told Healio | Orthopedics Today. “That means engineers and computer experts to help with the design, and mechanical experts that are responsible for the building of the implant. There is a lot of machinery involved in that process.”
Cost also increases with the manufacturing of the implant, according to Lewis.
“If you are doing a patient-specific implant, the manufacturing time and cost is generally going to be more than a traditional implant,” Lewis said.
One outstanding question that remains is whether 3D printing is worth the health care cost, according to Fox.
“Certainly, you do not want to 3D print everything, which may be a lot more expensive than something that is off the shelf when something off the shelf is acceptable,” he said.
Despite the concerns about costs, Abraham said the cost of 3D printing is not necessarily higher in the overall picture.
“There are cost savings in terms of OR time and also improved outcomes, but there are some increased costs upfront in terms of getting that done,” Abraham said.
Failure, complication rates
According to Mayerson, complication rates continue to be a challenge with 3D-printed implants.
“There are groups of surgeons who believe that the complication rate is too high to do them historically, and there have been studies that show that not reconstructing some parts of the pelvis leaves people with good function,” Mayerson said. “It is usually not the same as reconstructed function but because the complication rate is so high, there have been surgeons that have been trained and believe that [3D printing] is not worth doing.”
Rose said infection also remains a concern with 3D printing.
“Infections are higher with a more complicated surgery. Refining exactly how these are done to minimize the risk of infection is important,” Rose said.
However, Mayerson said further outreach and research could prevent failures from persisting as a barrier to the practical use of 3D printing in orthopedic oncology.
“One of the challenges is getting the word out that these work, and then determining the longevity of them and making sure the complication rate is less than what it has been in the past,” Mayerson told Healio | Orthopedics Today. “That will hopefully take these to the next level and the new generation of 3D-printed implants will hopefully have a greater utilization because they work and, by decreasing the operative time, they have hopefully decreased the infection rate.”
Strength, biocompatibility
Another potential issue is the strength of a 3D-printed implant, according to Lewis.
“Does [the 3D-printed implant] hold up to the large loads that the body experiences, especially the lower limb with weight-bearing?” Lewis said. “The force can exceed multiple times the body weight because of the activity of the muscles during walking, let alone other activities. So, you have to think about the short-term loading but also long-term loading because, as the physiologic loads are cycling, they occur many thousands of times. That can lead to fatigue failure of implants at stress concentrations and 3D printed metals can have different fatigue properties than traditionally manufactured parts.”
In addition, Lewis said the components are often 3D printed using a powder bed of titanium alloy and fusion by laser or electronic beam, which could lead to biocompatibility issues if the powders remain inside the components.
“The beam is precisely controlled to fuse a layer of the implant from the powder bed and the process is repeated layer by layer to build up the complete implant,” Lewis said. “But those powders can potentially be trapped inside a complex part or a lattice structure, and having those metal powders in the body is a big concern.”
Address the learning curve
As with other surgical techniques, Abraham said 3D printing comes with a learning curve.
“One of the things I will teach students and colleagues is: Just because you have a guide does not mean it is automatically going to go in perfectly,” Abraham said. “If you put the guide in 5° or 10° off, then every screw will be in the wrong place, everything is going the wrong way [and] you can still spear a nerve or cause other damage. There still is a technique involved, and it still has to be done carefully, and there is a learning curve to that.”
One way to address the learning curve associated with 3D printing could be increased education, which is currently lacking, during fellowship or through programs hosted by the Musculoskeletal Tumor Society, according to Siegel.
“There are small series of custom 3D printed outcome studies and case reports regarding 3D printed custom implants; however, specific technique articles on designing and implantation are limited in the literature,” Siegel said.
Future of 3D printing
Despite the concerns surrounding the use of 3D printing in orthopedic oncology, Fox said the evolutionary nature of 3D printing gives him a sense of hope for the future.
“It is a wonderful technology, and it is still in evolution,” Fox said. “There is always some new aspect of 3D printing that is coming out every year that continues to allow us to push the barriers in terms of production time, material types and biology, potentially, as well. Hopefully this offers patients long-term solutions, whereas there were none previously. I see it as a huge benefit in our armamentarium of managing patients with difficult situations.”
The most important aspect for the future, according to Rose, is the ability to scientifically prove that 3D printing can be an improvement on previous clinical practices in orthopedic oncology.
“It is always attractive to do something new, and hopefully every surgeon wants to innovate, but we have to be sure that we are making a net clinical benefit,” Rose said. “Studies will need to be done to be certain that the clinical outcome and the complication profile is better than what we had before.”
While innovative technologies may be exciting, Abraham said surgeon expertise will always remain necessary.
“I think these technologies are amazing, and they are exciting and encouraging, but they are never going to replace good judgment, careful thought, planning, skill and experience,” Abraham said.
- References:
- Kim Y, et al. Clin Exp Pediatr. 2022; doi:10.3345/cep.2022.00080.
- Morris JM, et al. Neuroimaging Clin N Am. 2023; doi:10.1016/j.nic.2023.05.001.
- Sternheim A, et al. ScienceDirect. 2018; doi:10.1016/B978-0-323-58118-9.00015-4.
- For more information:
- John A. Abraham, MD, of Abraham Orthopaedics, can be reached at jabraham@abrortho.com.
- Edward J. Fox, MD, of Penn State Health Milton S. Hershey Medical Center, can be reached at efox1@pennstatehealth.psu.edu.
- Gregory Lewis, PhD, of Penn State College of Medicine, can be reached at glewis1@pennstatehealth.psu.edu.
- Joel L. Mayerson, MD, FAAOS, FAOA, of The Ohio State University, can be reached at joel.mayerson@osumc.edu.
- Peter S. Rose, MD, FAAOS, of the Mayo Clinic, can be reached at rose.peter@mayo.edu.
- Herrick J. Siegel, MD, of the University of Alabama Birmingham Medical Center, can be reached at hsiegel@uabmc.edu.
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