Do surgeons need to utilize 3D printing in orthopedic oncology?
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Use caution
When applying new technology to any medical intervention, we should begin with the end in mind and ask what problem are we trying to solve and could this new technology cause more harm than current solutions.
In the field of orthopedic oncology, additive manufacturing can use computer-aided design software based on CT or MRI to produce surgical planning models, cutting guides for bone resection and custom endoprosthetic implants, as can the traditional subtractive manufacturing processes of casting, forging and machining. Benefits of additive manufacturing over traditional subtractive manufacturing include shorter manufacturing time, decreased costs in some cases and the ability to produce complex geometries, nanoscopic surfaces and internal porosity.
Despite its attraction, caution must be taken before making additive manufacturing an integral part of musculoskeletal oncologic care. Additive manufacturing creates a product based on CT or MRI with complex segmentation, 3D mesh or stereolithography file generation, layered printing and post-processing, all of which are subject to error that may be magnified at every step with potential devastating consequences. Tumors often progress from the time of imaging to the time of surgery, rendering the cutting guide or implant unable to fulfill oncologic or reconstructive goals. Additive manufacturing production of load-bearing implants with complex internal porosity may significantly alter the mechanical properties when compared to conventional implants, which may result in complications like fatigue failure. Accordingly, the FDA has issued guidance that additive manufacturing implants should be considered class III devices and pass through the 510(k), premarket approval, humanitarian device exemption or investigational device exemption pathways. Failure to do so and instead falling back on custom or compassionate use pathways may invite unwarranted scrutiny from federal regulators, especially if complications occur in the setting of financial conflicts of interest; furthermore, these regulatory hurdles may negate any temporal benefit gained from the additive manufacturing process. The complex resections commonly seen in oncology require higher image resolution, and increased man or computing power (hardware and software) in addition to the 3D printing process and post-processing, which can generate significant cost, especially compared to the human alternative.
Good surgical planning and precise surgical resection can be equally well-performed by a well-trained surgeon with well-honed 3D visuospatial skills who is well-attuned to the intricacies of oncologic surgery that are not evident on CT or MR. In most instances, complex reconstruction after resection can readily be performed with “off-the-shelf” implants or on a staged basis after the patient has recovered and the need for reconstruction has been determined. Dependence on additive manufacturing to surgically plan, resect or implant will diminish the surgeon’s acumen and skill in the long term and render both surgeon and patient vulnerable in the event such technology is not available.
When looking at the exciting world of additive manufacturing, we must be careful not to fall into the trap of approaching it as a technology looking for an application. Three-dimensional printing in surgical planning, resection and reconstruction can make the surgeon’s life easier and may eventually have a consistent place in our field, but it is not perfect, certainly not a necessity and should never supplant a diligent and experienced surgeon’s independent ability to handle any oncologic or reconstructive challenge that may arise.
- References:
- Carroll BE, et al. Acta Mater. 2015;doi:10.1016/j.actamat.2014.12.054.
- Leng S, et al. 3D Print Med. 2017;doi:10.1186/s41205-017-0014-3.
- Technical considerations for additive manufactured medical devices. https://www.fda.gov/regulatory-information/search-fda-guidance-documents/technical-considerations-additive-manufactured-medical-devices. Published: December 2017. Accessed: July 27, 2023.
- Wu Y, et al. Heliyon. 2023;doi:10.1016/j.heliyon.2023.e17718.
Daniel C. Allison MD, MBA, FACS, is the assistant director of orthopedic oncology at Cedars-Sinai Medical Center in Los Angeles.
Future of the subspecialty
Three-dimensional printing seems to be taking the orthopedic landscape by storm. Orthopedic oncology is no exception. The question remains: Do surgeons need to utilize 3D printing in orthopedic oncology? I do not believe any of us know the answer currently, but I do personally believe that it will be the future of the subspecialty. Three-dimensional printing offers a number of potential advantages in orthopedic oncology surgery, many of which are still unproven but make sense logically.
The first area of potential benefit would be improving bone and soft tissue ingrowth of implants. When placed on modular oncology implants, these highly porous 3D latices offer potential for better growth of bone and soft tissue into the device. Creating better bone incorporation of devices could lower rates of loosening, while improving soft tissue ingrowth could improve postoperative function through stronger muscle and tendon attachments.
The second area of interest involves 3D-printed cutting guides, which can potentially provide improvements in surgical resections of sarcomas. Three-dimensional printed, custom cutting guides provide surgeons with easy-to-use surgical guides which theoretically allow for more accurate and precise resections of bone cancers. Additionally, using similar guides for any allograft reconstruction can help match the void nearly perfectly.
The third area of interest lies in custom, 3D-printed surgical implants. Often after bone tumor resections, filling the void left behind can be technically challenging. Additionally, in locations such as the pelvis, these reconstructions have high failure rates. By creating custom, 3D-printed implants that perfectly match the size of the bone void, these reconstructions may be more easily performed with potentially fewer complications and more durability. Additionally, in the future, antibiotic coatings may be available to apply to these 3D-printed implants.
There are many potential areas of interest in orthopedic oncology and 3D printing. I have mentioned a few examples that many of us are excited about. The fact remains, however, that there is limited evidence to currently support the use of these new technologies. With more research being conducted on these techniques and outcomes, hopefully in the coming years, we can obtain a consensus on which work and which are just interesting, theoretical improvements.
- References:
- Dong C, et al. Surg Oncol. 2022;doi:10.1016/j.suronc.2022.101733.
- Gasparro MA, et al. Orthopedics. 2022;doi:10.3928/01477447-20211124-07.
- Guo Y, et al. Appl Bionics Biomech. 2022;doi:10.1155/2022/2801229.
- Park JW, et al. Sci Rep. 2022;doi:10.1038/s41598-022-22292-z.
- Wang M, et al. BMC Surg. 2022;doi:10.1186/s12893-022-01804-8.
Alan T. Blank, MD, MS, is an associate professor and clinical program co-director of musculoskeletal oncology at Rush University Cancer Center in Chicago. Austin Yu, BS, is a clinical research fellow in the section of orthopedic oncology at Rush University Medical Center in Chicago.
Important tool
As orthopedic oncologists, our surgical resections are often anatomically complex and reconstructions of those resections can be incredibly challenging. This is due to many factors but include considerations such as complex anatomy (particularly around the pelvis and spine), nonstandard bone cuts based on tumor location or desire for bone and soft tissue preservation, and approach difficulties because of non-resectable structures, such as neurovascular bundles.
In the past, options for reconstruction of anatomic bone resections included use of bulk allograft and custom or noncustom metal reconstructions. Each of these has its limitations and shortcomings.
Bulk allografts are often difficult and expensive to procure. Even when available, sizing remains a big issue, as the available donor bone may not exactly match the size of the patient bone. Moreover, allograft can often only be used in a nonstructural manner, not allowing immediate patient weightbearing. Adding to this is risk of infection, nonunion or malunion, fracture and resorption.
Custom metal implants have heretofore been a mainstay treatment option for reconstruction of complex defects post-tumor resection. They offer the advantage of allowing a strong structural reconstruction typically made of titanium, often allowing immediate or relatively rapid weightbearing. They can also be made in infinite shapes and sizes, which allow the surgeon to fill complex voids. However, they too have their own limitations. First, they take several weeks to model, design and manufacture. When time is of the essence, especially in malignant tumor surgery, this may not be feasible. In addition, they are expensive, carry risk of infection and do not always perfectly match the bone void, even when designed with the latest computer-aided design software using the patient’s CT and/or MRI.
Noncustom metal implants, by design, are off-the-shelf solutions which allow reconstruction, but cannot match the complex voids left behind during elaborate oncologic resections. Plus, they have many of the same shortcomings as custom implants.
Recently, 3D printing has entered the orthopedic oncology segment and, in many ways, has revolutionized our ability to treat our patients. These metal implants can be manufactured in rapid form using additive 3D printing and can be made in an infinite number of shapes, sizes and needs, based on surgeon preferences. Not only can we get them manufactured in near real-time, but we have the ability to add nuances to the implants to better aid our patients. For instance, we can bulk up the implant where structure is needed and add porosity to other portions based on the need for bone ingrowth or ongrowth, or even soft tissue attachment. There is no question that we need this technology to help us reconstruct complicated voids left behind after oncologic resections. It will remain an important tool in our armamentarium for our patients.
Shervin V. Oskouei, MD, is the division director of orthopedic oncology in the department of orthopedic surgery at Emory University School of Medicine in Atlanta.
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