Michael Barbella, Managing Editor05.27.15
Jason L. Koh seldom enters the operating room without first conducting a few procedural test runs.
The internationally known orthopedic surgeon usually formulates a treatment strategy long before he scrubs in, mentally rehearsing specific approaches and fixes based on the particular damage that awaits him.
Koh’s conceptual practice drills have served him well over the last two decades as he’s advanced his career and accepted more complicated cases. But they haven’t been entirely foolproof.
Every so often, Koh’s carefully honed plan is thrown for a loop by an unexpected snag on the operating table, whether it be injury extent or severity, an anatomical anomaly, or a rare miscalculation. He’s also been sidelined on occasion by exceptionally complex cases.
Koh faced such derailment potential fairly recently while treating a 25-year-old woman for trochlear dysplasia (an unstable kneecap). The patient had sustained several dislocations and underwent multiple repair surgeries but the procedures were unsuccessful because the damage had considerably worn away the natural groove (trochlea) in her left kneecap, causing the joint to easily slip off its intended track.
Trochlear dysplasia treatment is extremely complex, requiring initial assessments of overall alignment, tibial tubercle-trochlea groove angle, amount of patella alta (or, high-riding patella) and condition of the articular cartilage within the patellofemoral joint. Checking for arthritis is necessary too, as the disease easily can complicate potential remedies.
Surgically, trochlear dysplasia is an onerous beast to tame. Treatment varies depending on severity, ranging from medial patellofemoral ligament (MPFL) reconstruction, tibial tubercle osteotomy or trochleoplasty (where the femur’s distal aspect is cut and reshaped to create a more normal groove) to distal femoral osteotomy.
Since it replicates the medial patellofemoral ligament’s native shape, MPFL reconstruction generally provides the best possible stability in both knee flexion and extension. This option, however, usually is reserved for severe cases of patellar instability in which the trochlea no longer functions properly.
With her worn-down trochlea and recurrent dislocations, Koh’s patient clearly was an ideal candidate for MPFL reconstruction. And Koh certainly was the right choice for the job. But the procedure’s complexity as well as its associated risks (namely, cartilage death) prompted Koh to stray from his pretend practice drills.
“We don’t usually perform this procedure very frequently,” said Koh, M.D., chairman of orthopedic surgery at NorthShore University HealthSystem in Evanston, Ill., and director of the NorthShore Orthopaedic Institute. “I really care about my patients, and this is a very complicated surgery. I wanted something I could actually practice on beforehand.”
Koh found the perfect practice tool in 3-D-printed models of his patient’s damaged joint. Crafted from X-rays and computed tomography (CT) scan data, the life-sized replicas—anatomically flawless, particularly in matching the slope of the woman’s dome-shaped trochlea—allowed Koh to rehearse and fine-tune his intended approach before the live show.
“3-D printing actually allowed us to artificially simulate the procedure ahead of time. I had a specific plan about how I wanted to approach the knee but I found that when I started the procedure on the model, I had to finesse my technique a bit,” Koh told Orthopedic Design & Technology. “Part of the advantage of using the 3-D model is that the material was similar to bone, so I could determine whether I had to make certain cuts or adjust the angle to shape the trochlea the way I wanted. It was very beneficial to be able to practice the procedure a few times. It helped give me peace of mind.”
It also helped Koh and his surgical team perform a more efficient and effective procedure. By practicing repeatedly on the 3-D models, Koh ironed out the wrinkles in his MPFL reconstructive plan, thereby avoiding the impromptu adjustments and second-guessing that often accompany complicated surgeries.
Perhaps most importantly though, the 3-D models helped Koh improve patient care: Post-operative X-rays of the woman’s repaired knee showed a healed osteotomy with restoration of near-normal trochlear anatomy and an MPFL graft. The patient had not suffered any dislocations as of 12 months post-surgery.
“3-D printing allows us to have visual and tactile feedback on a complex orthopedic problem. It’s particularly useful in those cases where there’s a significant amount of deformity or dysplasia or damage, so that our normal anatomic understandings are not really as relevant,” Koh noted. “This is a great tool, and fortunately it’s a tool that allows us to practice on patients with significant abnormalities that we wouldn’t otherwise be able to practice on. If you can practice for an unusual procedure ahead of time, your chances of executing that procedure successfully are much greater.”
Pan Yu Lin, M.D., Guo Xiao Wei, M.D., and Mei Wei, M.D., surely would agree. The Zhengzhou, China-based orthopedic surgeons bolstered their success rate earlier this spring by honing their skills on a 3-D-printed replica of the spinal cord.
The model was based on the congenitally malformed spine of a 28-year-old woman named Yan who experienced a sudden onset of numbness that affected her ability to stand, walk and grasp items. Medical tests revealed a malformation in Yan’s third cervical vertebra, an abnormality that caused the nerves near the back of her spinal cord to compress (atlantoaxial dislocation) and constrict the blood supply to her extremities.
Yan’s treatment was both complicated and extremely risky, as it involved the spinal cord—one of the most delicate areas of the body in which to operate. With its 31 sets of nerves and constant data transfer between the brain and peripheral nervous system, there is little room for error—even the slightest false move can cause lifelong nerve damage, paralysis, or in rare cases, death.
Compounding that risk was the actual procedure to restore sensation to Yan’s limbs: The fix involved freeing soft tissue from the affected site, resetting the dislocation, and screwing everything back together without damaging the spinal cord. Quite the tall order.
To which 3-D printing provided the optimal solution. Like Koh, Yan’s surgeons first practiced the procedure on a 3-D-printed model before wheeling her into the operating room. And, they achieved similar results: Since the early May procedure at the Orthopaedic Hospital of Zhengzhou City, Yan has gradually regained strength and sensation in her extremities.
“Three-dimensional models provide us with another level of information we can use to take care of our patients,” noted Koh. “You can certainly get a lot of data from CT scans and simulations but actually being able to visualize, rotate and get a sense of what the anatomy is going to be like when you actually do the procedure and make the surgical approach is very helpful. For difficult cases where you have unusual or damaged anatomy, 3-D printing can be very useful as a way to practice or anticipate how you’re going to do a procedure. I think 3-D printing has a lot of interesting applications in orthopedic surgery.”
One of the most fascinating uses is the production of customized implants and instruments. Since they are based on patients’ own data (X-rays and CT scans), 3-D-printed replacement parts are precisely tailored for each individual, making them less prone to the loosening, instability and discomfort associated with many standardized joints.
The titanium hip designed and printed for Meryl Richards of Hampshire, England, for example, is devised to be structurally and materially superior to traditional implants. Created by Mobelife NV, the daughter firm of Leuven, Belgium-based Materialise NV, Richards’ new hip has a porous structure that is optimized for natural bone ingrowth and engineered to mimic the properties of bone, according to the company. Doctors deem the design a significant improvement over classic hip replacements, which sit on top of the bone and do not facilitate ingrowth.
The porous structure of Mobelife implants (the average porosity is 70 percent) also bests conventionally manufactured devices in both elasticity and thermal conductivity. Prevailing joint replacements are temperature-sensitive and unable to withstand impacts very well, whereas their porous brethren have an elasticity close to that of natural bone, enabling them to act as a shock absorber for large impacts. At the same time, the 3-D implants effectively exchange heat with their surroundings, thereby preventing the temperature-triggered pain common in traditional hips and knees.
To help improve the fit of Richards’ new hip and prevent any future problems (loosening, wear, tissue destruction), doctors “glued” the implant firmly in place with the woman’s own bone marrow stem cells.
Richards is not the only patient to benefit from Mobelife’s 3-D-printed implants. Three years ago, the technology spared a Swedish teenager from a wheelchair-bound existence.
The 15-year-old girl suffered from neurofibromatosis, a congenital disease characterized by the growth of nerve tumors. The condition destroyed the girl’s pelvis and left her with a skeletal deformation to her left hip. Just months after receiving her custom-made titanium hip cup in September 2012, the teenager was walking again; she was back at school less than a year and a half later.
Cases such as Richards, the unnamed Swedish teen and others—among them, the titanium pelvis printed for a British man, the lower jaw customized for an 83-year-old European woman, the vertebrae designed for a 12-year-old Chinese boy, the tracheas fashioned for three American baby boys with tracheobronchomalacia, and the new face given to a Wales motorcyclist—demonstrate the technology’s potential to fundamentally change orthopedics. But experts claim these cases are the exception rather than the rule, as most implants still are manufactured the traditional way.
“What I have learned is that implant customization is not the most important driver for the introduction of AM (additive manufacturing) in orthopedics, not if we are talking about the most common type of implants—the joint replacement implants for hips, knees and shoulders. The most important driver here is to be able to design and cost-efficiently manufacture implants with advanced trabecular structures. However, in all areas of orthopedics you might have complicated cases, sometimes caused by traumatic injuries or cancer, and that is a different thing. Here, you often have to use custom implants and AM can address that very efficiently, but, you don’t have a great volume of these cases compared to joint replacements,” noted Stefan Thundal, area sales manager/product manager for Arcam AB, a Swedish developer and provider of the additive manufacturing technology electron beam melting. “If the patient and the indication that you need to address is not unique, standard implants fit and work very, very well. There are some companies that claim the opposite but I don’t see that as a general trend. The vast majority are still using standard implants.
“If you look at the attention in the media for 3-D printing coupled to implants, there has been more attention drawn to custom implants. They are great cases to read about—they are always interesting as you have individual patients that you can relate to in terms of medical situation and how they’ve been helped,” he continued. “Those are great cases when you are focusing on the value it adds for individual patients, but in terms of where there is most use for 3-D printing, it’s not in the customization area.”
Rather, it’s most useful in customizing surgical instruments and cutting/drilling guides. Materialise, a provider of additive manufacturing software and 3-D printing solutions in the medical and industrial markets, uses its Mimics Innovation software to develop personalized guides for total knee replacements, complex wrist procedures, shoulder and ankle implants, and craniomaxillofacial reconstruction. The company’s cutting and drilling guides—based on CT, X-ray or magnetic resonance imaging—help clinicians make precise cuts at the desired location, angle and depth during procedures.
For example, Materialise created three customized guides to repair a severe arm deformity in a 51-year-old man. Two guides were used to drill holes for screws in their pre-determined positions, while the third pinpointed the precise osteotomy position. The company also printed a 3-D model of the deformed bone to ensure the guides were positionally accurate and led to the best fit.
“What we’re seeing more of today is custom instruments—cutting and drilling guides for the knee are probably some of the most popular instruments you see on the market, but these types of instruments are also being used in complex extremity cases, whether it’s a congenital defect, or perhaps a fracture that didn’t heal properly. We’re also seeing custom instruments in cases where there really isn’t an implant per se, in situations where you might be doing a high tibial osteotomy or a low femoral osteotomy,” said Colleen Wivell, Materialise’s biomedical engineering manager for North America. “What’s unique about these custom instruments is they are taking the pre-operative plan and transferring it exactly to the surgery. I think it’s adding very good value because it can reduce costs. Whenever you can actually streamline a surgery and make it faster, you’re saving time, and that’s significant. That’s where things really get traction. Patient outcomes become more important as well. If you can preplan and get a better patient outcome, that can have a big impact overall, too.”
Obviously, the greatest impact would come from 3-D-printed solutions that hit the winning trifecta of reducing operating room time, saving money and improving patient outcomes, but the technology is not quite there yet.
Trauma solutions provide some of the best patient outcomes, with companies like South Windsor, Conn.-based Oxford Performance Materials printing U.S. Food and Drug Administration-approved cranial and facial implants, and Dutch medtech design firm Xilloc Medical BV (the artisan of a 3-D-printed titanium jaw in 2011) developing a bone implant made from calcium phosphate, the primary constituent of natural bone. Xilloc’s artificially made material—dubbed CT-Bone—integrates with the body like natural bone.
Stratasys Ltd. also is advancing trauma care with its handiwork in orbital fracture repair. The global provider of 3-D printing and additive manufacturing solutions is collaborating with experts at the Hong Kong Polytechnic University Industrial Center to make customized eye socket implants containing sterilizable material.
Using CT scan and X-ray data, Hong Kong doctors reconstruct the “orbital floor” of a patient’s eye socket with CAD (computer-aided design) software, and then print two layered molds—an upper and lower—into which a thin titanium sheet is pressed. The molds, comprised of a heat-resistant, biocompatible thermoplastic, are printed on Stratasys’ Fortus 3-D Production System.
“Craniomaxillofacial (CMF) surgeons have taken the lead in adopting 3-D printing technology,” said Scott Rader, general manager for medical solutions at Stratasys. “The adoption has been driven by the fact that our facial appearance is what we present to the world, and the need for more accurate and precise reconstruction of facial features. Beyond the example of making molds for titanium implants, imagine the complexity of translating a straight-line leg bone autograft (a graft of a patient’s own bone, commonly the fibula of the lower leg) with a free flap surgery into a three-dimensional curved structure of the jaw. This is where it started—CMF surgeons used 3-D-printed cutting guides to shorten the time of surgery, and translate a straight bone to a curved jaw. This really was the genesis of trying to correct the anatomical defects that can occur from cancer, infection or trauma, which can be quite debilitating to appearance or ability to eat, and has been a major driver of adoption.”
” But adoption of 3-D printing has also been about asking the question why it matters, and what matters in medicine is not that you’re using 3-D printing, what really matters is the outcomes for the patients and the economics of delivering quality care,” Rader continued. ”Good outcomes are what are desired by both the patient and physician —does the patient get better when they seek care. The anecdotal evidence to date in terms of time savings has been very well publicized by a number of physicians, demonstrating the potential for economic cost savings of expensive time in an operating room, and now the field is moving into the stage where it’s proving both clinical gains and economic benefits out in clinical trials.”
Indeed, 3-D printing is, in many respects, the mobile, want-it-now world’s dream manufacturing mode, capable of producing items in minutes or hours rather than days or weeks. 3-D-printed objects generally are created using an additive process (hence its “additive manufacturing” alias) that involves spreading successive microscopic layers of plastic or metal fused by lasers or ultraviolet light. Each of the layers can be seen as a thinly sliced horizontal cross-section of the eventual object.
The process is ideal for creating complex designs and corporal practice models for surgeons. The technology’s geometric design freedom is particularly useful in orthopedics, enabling engineers to devise more natural anatomical shapes and incorporate porous bone replacement scaffolds into the finished product.
But the technology is not (yet) the manufacturing panacea portrayed by enthusiasts. Although it trumps traditional methods in limited assembly runs and prototyping, it 3-D printing doesn’t scale very well, making it an unlikely option for the mass production of large joint replacements, experts note.
“In general, 3-D printing gives the most benefit when producing custom-shaped components. Although the productivity is increasing year after year, the actual part volume plays a role in the final manufacturing cost of the implant or instrument,” explained a company statement from 3D Systems Inc., a Rock Hill, S.C.-based provider of 3-D digital design and fabrication solutions, including 3-D printers, print materials and cloud-sourced custom parts. “The economic benefit of 3-D printing is obvious in certain application areas, whereas in other areas, productivity of the 3-D printing should still be higher in order to achieve lower manufacturing costs compared to classical casting and forging technology. Ongoing and future technology developments will continue to improve 3-D printing productivity and this will gradually result in similar or better economics for 3-D printing technology.”
Proponents of the technology readily concede its drawbacks, noting the process was never intended to replace large-scale manufacturing. The advantages of 3-D printing, they say, lie in the alternatives it provides to traditional production systems. Mass appeal items, for example, are best manufactured through injection molding, but that process has its limitations as well, requiring companies to create a different mold for each different part produced. If a part’s specifications change, a new mold must be made.
3-D printed objects, however, require no mold, only a computer model that can be updated at any time. In addition, 3-D printing easily can handle complex designs and print an item with multiple parts all at once. Such a feat is impossible with injection molding, as the process necessitates parts be manufactured separately and then assembled.
Despite its limitations, additive manufacturing is expected to grow substantially over the next several years, expanding 13.5 percent annually to top $3.5 billion by 2017, according to the 2014 “Wohlers Report on Additive Manufacturing and 3-D Printing.” Models and implants for use in dental and medical procedures were among the top five applications of the technology last year, the study found.
Nevertheless, 3-D printing is not likely to replace traditional medtech manufacturing completely in the near future (or distant one, for that matter), experts contend, because it does not produce the finished orthopedic device components directly out of the machine.
“I am absolutely convinced that the use of additive manufacturing will continue to grow dramatically. But there is a common misperception that additive manufacturing completely replaces traditional machining,” Arcam’s Thundal said. “The truth is that additive manufacturing replaces some of the machining steps (or casting, or forging) but AM-built components are in almost all cases post-processed with machining. Some components need more machining, some less, it depends on the technical requirements of the component. But even with the finest finish you can possibly get today with additive manufacturing, you still need to machine surfaces that need to be assembled to other components.”
“Take one of the best examples of additive manufacturing to date, the hip cup that goes into the pelvis. On the outside surface of this cup you have a porous trabecular structure, which is used for bone ingrowth and bone integration,” he continued. “But inside the cup, you need to have either a ceramic or polymer liner. To fit the liner into the cup, you have to have a very exact finish. A raw surface is not adequate or accurate enough, so you need to machine the inside of the cup. The most successful companies will be the ones that master the art of combining 3-D printing and traditional machining in a smart way.”
The internationally known orthopedic surgeon usually formulates a treatment strategy long before he scrubs in, mentally rehearsing specific approaches and fixes based on the particular damage that awaits him.
Koh’s conceptual practice drills have served him well over the last two decades as he’s advanced his career and accepted more complicated cases. But they haven’t been entirely foolproof.
Every so often, Koh’s carefully honed plan is thrown for a loop by an unexpected snag on the operating table, whether it be injury extent or severity, an anatomical anomaly, or a rare miscalculation. He’s also been sidelined on occasion by exceptionally complex cases.
Koh faced such derailment potential fairly recently while treating a 25-year-old woman for trochlear dysplasia (an unstable kneecap). The patient had sustained several dislocations and underwent multiple repair surgeries but the procedures were unsuccessful because the damage had considerably worn away the natural groove (trochlea) in her left kneecap, causing the joint to easily slip off its intended track.
Trochlear dysplasia treatment is extremely complex, requiring initial assessments of overall alignment, tibial tubercle-trochlea groove angle, amount of patella alta (or, high-riding patella) and condition of the articular cartilage within the patellofemoral joint. Checking for arthritis is necessary too, as the disease easily can complicate potential remedies.
Surgically, trochlear dysplasia is an onerous beast to tame. Treatment varies depending on severity, ranging from medial patellofemoral ligament (MPFL) reconstruction, tibial tubercle osteotomy or trochleoplasty (where the femur’s distal aspect is cut and reshaped to create a more normal groove) to distal femoral osteotomy.
Since it replicates the medial patellofemoral ligament’s native shape, MPFL reconstruction generally provides the best possible stability in both knee flexion and extension. This option, however, usually is reserved for severe cases of patellar instability in which the trochlea no longer functions properly.
With her worn-down trochlea and recurrent dislocations, Koh’s patient clearly was an ideal candidate for MPFL reconstruction. And Koh certainly was the right choice for the job. But the procedure’s complexity as well as its associated risks (namely, cartilage death) prompted Koh to stray from his pretend practice drills.
“We don’t usually perform this procedure very frequently,” said Koh, M.D., chairman of orthopedic surgery at NorthShore University HealthSystem in Evanston, Ill., and director of the NorthShore Orthopaedic Institute. “I really care about my patients, and this is a very complicated surgery. I wanted something I could actually practice on beforehand.”
Koh found the perfect practice tool in 3-D-printed models of his patient’s damaged joint. Crafted from X-rays and computed tomography (CT) scan data, the life-sized replicas—anatomically flawless, particularly in matching the slope of the woman’s dome-shaped trochlea—allowed Koh to rehearse and fine-tune his intended approach before the live show.
“3-D printing actually allowed us to artificially simulate the procedure ahead of time. I had a specific plan about how I wanted to approach the knee but I found that when I started the procedure on the model, I had to finesse my technique a bit,” Koh told Orthopedic Design & Technology. “Part of the advantage of using the 3-D model is that the material was similar to bone, so I could determine whether I had to make certain cuts or adjust the angle to shape the trochlea the way I wanted. It was very beneficial to be able to practice the procedure a few times. It helped give me peace of mind.”
It also helped Koh and his surgical team perform a more efficient and effective procedure. By practicing repeatedly on the 3-D models, Koh ironed out the wrinkles in his MPFL reconstructive plan, thereby avoiding the impromptu adjustments and second-guessing that often accompany complicated surgeries.
Perhaps most importantly though, the 3-D models helped Koh improve patient care: Post-operative X-rays of the woman’s repaired knee showed a healed osteotomy with restoration of near-normal trochlear anatomy and an MPFL graft. The patient had not suffered any dislocations as of 12 months post-surgery.
“3-D printing allows us to have visual and tactile feedback on a complex orthopedic problem. It’s particularly useful in those cases where there’s a significant amount of deformity or dysplasia or damage, so that our normal anatomic understandings are not really as relevant,” Koh noted. “This is a great tool, and fortunately it’s a tool that allows us to practice on patients with significant abnormalities that we wouldn’t otherwise be able to practice on. If you can practice for an unusual procedure ahead of time, your chances of executing that procedure successfully are much greater.”
Pan Yu Lin, M.D., Guo Xiao Wei, M.D., and Mei Wei, M.D., surely would agree. The Zhengzhou, China-based orthopedic surgeons bolstered their success rate earlier this spring by honing their skills on a 3-D-printed replica of the spinal cord.
The model was based on the congenitally malformed spine of a 28-year-old woman named Yan who experienced a sudden onset of numbness that affected her ability to stand, walk and grasp items. Medical tests revealed a malformation in Yan’s third cervical vertebra, an abnormality that caused the nerves near the back of her spinal cord to compress (atlantoaxial dislocation) and constrict the blood supply to her extremities.
Yan’s treatment was both complicated and extremely risky, as it involved the spinal cord—one of the most delicate areas of the body in which to operate. With its 31 sets of nerves and constant data transfer between the brain and peripheral nervous system, there is little room for error—even the slightest false move can cause lifelong nerve damage, paralysis, or in rare cases, death.
Compounding that risk was the actual procedure to restore sensation to Yan’s limbs: The fix involved freeing soft tissue from the affected site, resetting the dislocation, and screwing everything back together without damaging the spinal cord. Quite the tall order.
To which 3-D printing provided the optimal solution. Like Koh, Yan’s surgeons first practiced the procedure on a 3-D-printed model before wheeling her into the operating room. And, they achieved similar results: Since the early May procedure at the Orthopaedic Hospital of Zhengzhou City, Yan has gradually regained strength and sensation in her extremities.
“Three-dimensional models provide us with another level of information we can use to take care of our patients,” noted Koh. “You can certainly get a lot of data from CT scans and simulations but actually being able to visualize, rotate and get a sense of what the anatomy is going to be like when you actually do the procedure and make the surgical approach is very helpful. For difficult cases where you have unusual or damaged anatomy, 3-D printing can be very useful as a way to practice or anticipate how you’re going to do a procedure. I think 3-D printing has a lot of interesting applications in orthopedic surgery.”
One of the most fascinating uses is the production of customized implants and instruments. Since they are based on patients’ own data (X-rays and CT scans), 3-D-printed replacement parts are precisely tailored for each individual, making them less prone to the loosening, instability and discomfort associated with many standardized joints.
The titanium hip designed and printed for Meryl Richards of Hampshire, England, for example, is devised to be structurally and materially superior to traditional implants. Created by Mobelife NV, the daughter firm of Leuven, Belgium-based Materialise NV, Richards’ new hip has a porous structure that is optimized for natural bone ingrowth and engineered to mimic the properties of bone, according to the company. Doctors deem the design a significant improvement over classic hip replacements, which sit on top of the bone and do not facilitate ingrowth.
The porous structure of Mobelife implants (the average porosity is 70 percent) also bests conventionally manufactured devices in both elasticity and thermal conductivity. Prevailing joint replacements are temperature-sensitive and unable to withstand impacts very well, whereas their porous brethren have an elasticity close to that of natural bone, enabling them to act as a shock absorber for large impacts. At the same time, the 3-D implants effectively exchange heat with their surroundings, thereby preventing the temperature-triggered pain common in traditional hips and knees.
To help improve the fit of Richards’ new hip and prevent any future problems (loosening, wear, tissue destruction), doctors “glued” the implant firmly in place with the woman’s own bone marrow stem cells.
Richards is not the only patient to benefit from Mobelife’s 3-D-printed implants. Three years ago, the technology spared a Swedish teenager from a wheelchair-bound existence.
The 15-year-old girl suffered from neurofibromatosis, a congenital disease characterized by the growth of nerve tumors. The condition destroyed the girl’s pelvis and left her with a skeletal deformation to her left hip. Just months after receiving her custom-made titanium hip cup in September 2012, the teenager was walking again; she was back at school less than a year and a half later.
Cases such as Richards, the unnamed Swedish teen and others—among them, the titanium pelvis printed for a British man, the lower jaw customized for an 83-year-old European woman, the vertebrae designed for a 12-year-old Chinese boy, the tracheas fashioned for three American baby boys with tracheobronchomalacia, and the new face given to a Wales motorcyclist—demonstrate the technology’s potential to fundamentally change orthopedics. But experts claim these cases are the exception rather than the rule, as most implants still are manufactured the traditional way.
“What I have learned is that implant customization is not the most important driver for the introduction of AM (additive manufacturing) in orthopedics, not if we are talking about the most common type of implants—the joint replacement implants for hips, knees and shoulders. The most important driver here is to be able to design and cost-efficiently manufacture implants with advanced trabecular structures. However, in all areas of orthopedics you might have complicated cases, sometimes caused by traumatic injuries or cancer, and that is a different thing. Here, you often have to use custom implants and AM can address that very efficiently, but, you don’t have a great volume of these cases compared to joint replacements,” noted Stefan Thundal, area sales manager/product manager for Arcam AB, a Swedish developer and provider of the additive manufacturing technology electron beam melting. “If the patient and the indication that you need to address is not unique, standard implants fit and work very, very well. There are some companies that claim the opposite but I don’t see that as a general trend. The vast majority are still using standard implants.
“If you look at the attention in the media for 3-D printing coupled to implants, there has been more attention drawn to custom implants. They are great cases to read about—they are always interesting as you have individual patients that you can relate to in terms of medical situation and how they’ve been helped,” he continued. “Those are great cases when you are focusing on the value it adds for individual patients, but in terms of where there is most use for 3-D printing, it’s not in the customization area.”
Rather, it’s most useful in customizing surgical instruments and cutting/drilling guides. Materialise, a provider of additive manufacturing software and 3-D printing solutions in the medical and industrial markets, uses its Mimics Innovation software to develop personalized guides for total knee replacements, complex wrist procedures, shoulder and ankle implants, and craniomaxillofacial reconstruction. The company’s cutting and drilling guides—based on CT, X-ray or magnetic resonance imaging—help clinicians make precise cuts at the desired location, angle and depth during procedures.
For example, Materialise created three customized guides to repair a severe arm deformity in a 51-year-old man. Two guides were used to drill holes for screws in their pre-determined positions, while the third pinpointed the precise osteotomy position. The company also printed a 3-D model of the deformed bone to ensure the guides were positionally accurate and led to the best fit.
“What we’re seeing more of today is custom instruments—cutting and drilling guides for the knee are probably some of the most popular instruments you see on the market, but these types of instruments are also being used in complex extremity cases, whether it’s a congenital defect, or perhaps a fracture that didn’t heal properly. We’re also seeing custom instruments in cases where there really isn’t an implant per se, in situations where you might be doing a high tibial osteotomy or a low femoral osteotomy,” said Colleen Wivell, Materialise’s biomedical engineering manager for North America. “What’s unique about these custom instruments is they are taking the pre-operative plan and transferring it exactly to the surgery. I think it’s adding very good value because it can reduce costs. Whenever you can actually streamline a surgery and make it faster, you’re saving time, and that’s significant. That’s where things really get traction. Patient outcomes become more important as well. If you can preplan and get a better patient outcome, that can have a big impact overall, too.”
Obviously, the greatest impact would come from 3-D-printed solutions that hit the winning trifecta of reducing operating room time, saving money and improving patient outcomes, but the technology is not quite there yet.
Trauma solutions provide some of the best patient outcomes, with companies like South Windsor, Conn.-based Oxford Performance Materials printing U.S. Food and Drug Administration-approved cranial and facial implants, and Dutch medtech design firm Xilloc Medical BV (the artisan of a 3-D-printed titanium jaw in 2011) developing a bone implant made from calcium phosphate, the primary constituent of natural bone. Xilloc’s artificially made material—dubbed CT-Bone—integrates with the body like natural bone.
Stratasys Ltd. also is advancing trauma care with its handiwork in orbital fracture repair. The global provider of 3-D printing and additive manufacturing solutions is collaborating with experts at the Hong Kong Polytechnic University Industrial Center to make customized eye socket implants containing sterilizable material.
Using CT scan and X-ray data, Hong Kong doctors reconstruct the “orbital floor” of a patient’s eye socket with CAD (computer-aided design) software, and then print two layered molds—an upper and lower—into which a thin titanium sheet is pressed. The molds, comprised of a heat-resistant, biocompatible thermoplastic, are printed on Stratasys’ Fortus 3-D Production System.
“Craniomaxillofacial (CMF) surgeons have taken the lead in adopting 3-D printing technology,” said Scott Rader, general manager for medical solutions at Stratasys. “The adoption has been driven by the fact that our facial appearance is what we present to the world, and the need for more accurate and precise reconstruction of facial features. Beyond the example of making molds for titanium implants, imagine the complexity of translating a straight-line leg bone autograft (a graft of a patient’s own bone, commonly the fibula of the lower leg) with a free flap surgery into a three-dimensional curved structure of the jaw. This is where it started—CMF surgeons used 3-D-printed cutting guides to shorten the time of surgery, and translate a straight bone to a curved jaw. This really was the genesis of trying to correct the anatomical defects that can occur from cancer, infection or trauma, which can be quite debilitating to appearance or ability to eat, and has been a major driver of adoption.”
” But adoption of 3-D printing has also been about asking the question why it matters, and what matters in medicine is not that you’re using 3-D printing, what really matters is the outcomes for the patients and the economics of delivering quality care,” Rader continued. ”Good outcomes are what are desired by both the patient and physician —does the patient get better when they seek care. The anecdotal evidence to date in terms of time savings has been very well publicized by a number of physicians, demonstrating the potential for economic cost savings of expensive time in an operating room, and now the field is moving into the stage where it’s proving both clinical gains and economic benefits out in clinical trials.”
Indeed, 3-D printing is, in many respects, the mobile, want-it-now world’s dream manufacturing mode, capable of producing items in minutes or hours rather than days or weeks. 3-D-printed objects generally are created using an additive process (hence its “additive manufacturing” alias) that involves spreading successive microscopic layers of plastic or metal fused by lasers or ultraviolet light. Each of the layers can be seen as a thinly sliced horizontal cross-section of the eventual object.
The process is ideal for creating complex designs and corporal practice models for surgeons. The technology’s geometric design freedom is particularly useful in orthopedics, enabling engineers to devise more natural anatomical shapes and incorporate porous bone replacement scaffolds into the finished product.
But the technology is not (yet) the manufacturing panacea portrayed by enthusiasts. Although it trumps traditional methods in limited assembly runs and prototyping, it 3-D printing doesn’t scale very well, making it an unlikely option for the mass production of large joint replacements, experts note.
“In general, 3-D printing gives the most benefit when producing custom-shaped components. Although the productivity is increasing year after year, the actual part volume plays a role in the final manufacturing cost of the implant or instrument,” explained a company statement from 3D Systems Inc., a Rock Hill, S.C.-based provider of 3-D digital design and fabrication solutions, including 3-D printers, print materials and cloud-sourced custom parts. “The economic benefit of 3-D printing is obvious in certain application areas, whereas in other areas, productivity of the 3-D printing should still be higher in order to achieve lower manufacturing costs compared to classical casting and forging technology. Ongoing and future technology developments will continue to improve 3-D printing productivity and this will gradually result in similar or better economics for 3-D printing technology.”
Proponents of the technology readily concede its drawbacks, noting the process was never intended to replace large-scale manufacturing. The advantages of 3-D printing, they say, lie in the alternatives it provides to traditional production systems. Mass appeal items, for example, are best manufactured through injection molding, but that process has its limitations as well, requiring companies to create a different mold for each different part produced. If a part’s specifications change, a new mold must be made.
3-D printed objects, however, require no mold, only a computer model that can be updated at any time. In addition, 3-D printing easily can handle complex designs and print an item with multiple parts all at once. Such a feat is impossible with injection molding, as the process necessitates parts be manufactured separately and then assembled.
Despite its limitations, additive manufacturing is expected to grow substantially over the next several years, expanding 13.5 percent annually to top $3.5 billion by 2017, according to the 2014 “Wohlers Report on Additive Manufacturing and 3-D Printing.” Models and implants for use in dental and medical procedures were among the top five applications of the technology last year, the study found.
Nevertheless, 3-D printing is not likely to replace traditional medtech manufacturing completely in the near future (or distant one, for that matter), experts contend, because it does not produce the finished orthopedic device components directly out of the machine.
“I am absolutely convinced that the use of additive manufacturing will continue to grow dramatically. But there is a common misperception that additive manufacturing completely replaces traditional machining,” Arcam’s Thundal said. “The truth is that additive manufacturing replaces some of the machining steps (or casting, or forging) but AM-built components are in almost all cases post-processed with machining. Some components need more machining, some less, it depends on the technical requirements of the component. But even with the finest finish you can possibly get today with additive manufacturing, you still need to machine surfaces that need to be assembled to other components.”
“Take one of the best examples of additive manufacturing to date, the hip cup that goes into the pelvis. On the outside surface of this cup you have a porous trabecular structure, which is used for bone ingrowth and bone integration,” he continued. “But inside the cup, you need to have either a ceramic or polymer liner. To fit the liner into the cup, you have to have a very exact finish. A raw surface is not adequate or accurate enough, so you need to machine the inside of the cup. The most successful companies will be the ones that master the art of combining 3-D printing and traditional machining in a smart way.”