Michael Barbella, Managing Editor04.02.14
The end is coming. Ready or not, like it or not—it’s coming. And coming quickly. Renowned futurist Raymond Kurzweil predicts humanity has only 31 years of cerebral dominance left before it succumbs to ultra-intelligent machines. By 2045, he reckons, the computers we’ve spent decades building and programming not only will be infinitely smarter than us, they’ll ironically also have the ability to ration, reason and feel like the frontal, temporal and parietal lobes of an organic brain.
At that point—in the Year of Singularity—computer intelligence will be roughly 1 billion times as powerful as the sum of all human intellect. Mankind’s reign on planet Earth will be over, prompting a societal transformation that Kurzweil calls “a singular change in human history.”
Or, the press of the “delete” key.
Or, maybe it doesn’t end at all. Kurzweil is confident that artificial intelligence dramatically will improve and eventually help extend the human experience. Expert systems will eradicate viruses through rapid DNA sequencing; they’ll create new body parts (already occurring through 3-D printing); and perhaps most impressively, they’ll reprogram the body’s “stone-age software” to halt the aging process, allowing man to achieve his ultimate dream of immortality. In Kurzweil’s future world, humans will be able to sprint for 15 minutes without taking a breath or go scuba diving with no gear. He also expects nanotechnology to significantly enhance our mental capabilities, and virtual reality to become a ubiquitous daily experience.
“We’re going to become increasingly non-biological to the point where the non-biological part dominates and the biological part is not important anymore,” Kurzweil said during last year’s Global Future 2045 International Congress. “In fact, the non-biological part—the machine part—will be so powerful it can completely model and understand the biological part. So even if that biological part went away it wouldn’t make any difference. We’ll also have non-biological bodies—we can create bodies with nanotechnology, we can create virtual bodies and virtual reality in which the virtual reality will be as realistic as the actual reality. I think we’ll have a choice of bodies…we’ll have different ways we can create bodies.”
Full-body construction is still a bit too advanced for the human brain’s 100 billion neurons (though exoskeletons and the walking, talking 6-foot-tall bionic robot currently housed at the Smithsonian Museum arguably measure up—in a rudimentary, pre-Singularity kind of way). Nevertheless, the cerebral cortex has become quite adept through the centuries at creating body parts: Ancient Egyptians crafted jawbone implants from ivory while the Maya preferred shells (their calcium carbonate purportedly integrated well with bone). The Romans’ proclivity for gold cranium implants was mimicked several millennia later by the Incas of Peru, although the doomed society also liked silver for skull repairs.
Twentieth-century advances in biomaterial science have created more superior body parts and biologically worthy substances. Most joint replacements, for example, are made of a stainless steel, zirconium, titanium, polyethylene and in certain cases, ceramic mix; prosthetic limbs are comprised of a carbon-fiber composite/polypropylene or polyethylene blend; artificial ears are made from silicone or spider silk, and some cranial implants consist of ultra high-performance polyetherketoneketone (PEKK).
Twenty-first-century innovations have expanded the list of medical materials well beyond the traditional metals and polymers to include diamond (retinal implants), lutetium oxyorthosilicate (X-ray imaging), gold (diagnostics), shrimp shells/silk (sutures, biological scaffolds) and glass (bone repair). Such options, however, are off-limits in the orthopedic sector, where manufacturers remain staunchly loyal to reliable veterans like PEKK, polyethylene, stainless steel, cobalt chromium and titanium, an overall favorite.
“Titanium continues to be the metal of choice for the major [orthopedic] OEMs—DePuy (Synthes), Medtronic, Biomet, Wright and Zimmer. We have no doubt they all are working with other materials, but titanium properties lend themselves very nicely to implants,” noted David Yoho, senior vice president at Vulcanium Metals International LLC, a global distributor of titanium mill products for various industries, including medical. “Titanium is lightweight, it’s strong and it’s biocompatible, that’s why the implant manufacturers love it. The material is used for nearly any type of implant you can think of—hip, knees, spinal, maxillofacial, pacemakers. It’s a wonderful material.”
So wonderful, in fact, that it often trumps other substances. Whether in natural form or chemically modified, titanium is used literally from head to toe in the human body, connecting joints, reinforcing bones, restoring vision, detecting sound waves and fusing vertebrae. Most, if not all, orthopedic OEMs sell titanium hips and/or knees, bone screws, nails, plates and cervical cages (Wright Medical Technology Inc. is the sole exception, though the company offers a line of thumb and hand/wrist implants).
Zimmer Holdings Inc. was an early Ti-6Al-4V convert, developing a “Natural Knee” System in 1985 that featured a cancellous-structured titanium porous coating option for better fixation. Executives claim the Knee—implanted in more than 400,000 patients globally since its introduction—was one of the first to replicate the human anatomy by duplicating the tibia’s asymmetrical shape.
Many of Zimmer’s rivals have followed suit over the years with their own attempts to mimic Mother Nature’s handiwork: Stryker Corp.’s Triathlon Total Knee Replacement System features shorter posterior condyles and a geometry designed to enhance the implant’s contact area, providing recipients with a natural knee rotation through 150+ degrees of flexion, while the Gription Titanium Foam implants from DePuy Synthes are tailored for patients missing bone in the tibial or femoral areas (the material—a porous structure made from commercially pure titanium—reportedly has a similar elasticity to bone and a coefficient of friction that allows for initial scratch fit).
“Everyone is trying to differentiate themselves from their competitors. We’re seeing more and more customers calling for specific chemical and physical properties in their materials—either higher or lower tensile strength, custom tolerances…it really depends on the application,” Yoho told Orthopedic Design & Technology. “If it’s a spinal implant or some type of trauma plate, you’re going to want specific [material] properties to make it perform as intended. If it’s a joint implant, you’ll want the material to be wear resistant and give maximum range of motion. There are various types of physical and chemical properties that may be required, and certain materials are better suited for certain applications. There are new [material] products coming out, but if it’s not titanium, there’s not a lot of conversation or buzz about it.”
There’s good reason for that buzz: Ti-6Al-4V is lightweight, strong, and impervious to the body’s corrosive bath of extracellular tissue fluid. The material also is more flexible than other metals and can withstand the incredible loads/stresses placed upon the lower joints. In addition, the non-ferrous element is compatible with magnetic resonance imaging and computed tomography scans.
Augmenting titanium’s mass appeal in recent years was the development of aluminum and vanadium-free grades (both metals have been linked to Alzheimer’s disease, neuropathy and ostemomalacia) as well as brands with antibacterial coatings. The metal could become even more popular in the future if researchers can improve its integration to living bone.
Clinicians in China and Japan may be close—they currently are experimenting with a urease fabrication process for coating titanium implants with bioactive calcium phosphate (CaP)/gelatin composites. The analysts implanted tiny 2-by-10-millimeter CaP/gelatin/titanium and CaP/titanium rods into the thigh bones of rabbits, using pure titanium rods as controls. Four and eight weeks after the surgery, the researchers noticed considerably more new bone on the surface of the composite CaP/gelatin/titanium rods than in the other two groups. Moreover, the CaP/gelatin/titanium rods bonded to the surrounding bone directly, with no intervening soft tissue layer, according to Science and Technology of Advanced Materials.
The results suggest that CaP/gelatin/titanium implants made from the researchers’ urease process not only can enhance the proliferation of stem cells and differentiation of bone cells, but also the bone bonding ability of the implant itself. “Such CaP/gel functionalized Ti might have great potential in joint replacements or dental implants,” the study authors wrote.
Pollyannaish on Polymers
While it remains a popular choice among orthopedic device manufacturers, titanium is far from a perfect implant material. For starters, it has poor shear strength, making it an inferior option for bone screws, rods, plates and similar applications (implant makers obviously disagree). The material also is prone to notching when it is bent or attached to pedicle screws, thereby increasing its proclivity to fatigue failure.
Perhaps more importantly, though, titanium tends to wear significantly when it is rubbed between itself or other metals, resulting in potentially harmful debris that can cause pain and loosen implants. Studies have shown titanium femoral heads wear substantially more than their cobalt-chrome-molybdenum (Co-Cr-Mo) and 316L stainless steel counterparts, averaging 74.3 percent degradation against high molecular weight polyethylene acetabular components (Co-Cr-Mo femoral heads produced the least amount of wear debris, according to research data). Clinical trials have reached similar conclusions, finding higher metal concentrations in tissue surrounding titanium prostheses than Co-Cr-Mo or stainless steel implants.
“There are precious few materials in orthopedics,” said Scott DeFelice, president and CEO of Oxford Performance Materials, a South Windsor, Conn.-based developer of ultra-high performance thermoplastic biomedical polymers. “Titanium has been the material of choice for a lot of reasons—predominantly for its biocompatibility, which is pretty well known. But it has a couple of things working against it. The biggest disadvantage is that titanium is stiffer than bone. The more conformal an [orthopedic] implant is to the bone, the longer its life will be and the healthier the bone will be. We’re now starting to see a generation of revision hip surgeries that is being driven by many factors, but quite often these surgeries are due to the material being too robust. It’s entirely appropriate given the stake of the science, but the industry is beginning to move toward material options that are more biochemically compatible with the body.”
Many of those options involve plastics like PEKK, polyetheretherketone (PEEK), polycaprolactone, polylactide (PLA), polyglycolide (PGA) and PLA-PGA combinations. DeFelice’s firm makes a 3-D printed cranial implant from PEKK, an osteoconductive material with similar mechanical properties as bone and twice the compressive strength of its sister ketone polymer, PEEK. The semi-crystalline thermoplastic siblings are quickly gaining ground on their metallic rivals, charming manufacturers with their high heat and chemical resistance, as well as their ability to withstand high mechanical loads.
PEEK’s allure intensified last summer after a seven-year-long clinical study determined the material is better than titanium at maintaining intervertebral height and cervical lordosis in the surgical treatment of cervical spondylotic myelopathy (CSM). A research team from Changzhen Hospital in Shanghai, China, designed the study to compare the outcomes of titanium and PEEK cages and discovered the titanium cage group demonstrated “significantly inferior outcomes” compared with the PEEK group.
Though it received little attention, the study reinforced PEEK’s capabilities as a viable orthopedic implant. Pioneered in 1999 by United Kingdom-based Invibio Biomaterial Solutions, implantable PEEK polymers have been developed in various formulations, ranging from unfilled grades with varying molecular weight to image-contrast and carbon fiber-reinforced versions (the latter helps eliminate environmental stress cracking, experts claim). The image-contrast class can contain metal wires (markers) or barium sulfate power to make them visible in X-rays.
“There’s been more of a calling for that kind of material,” said Mike Feld, sales development manager for Interstate Plastics, a multi-branch industrial plastics distributor and manufacturer headquartered in Sacramento, Calif. “Plastics are transparent under X-rays but with an additive they become visible. Sometimes you need the implant to be visible to be sure it is in the right place. Arthroscopy is more popular than ever…nobody is making a big cut anymore to go into the body. It’s all done through pinholes with cameras. When you’re not opening up the knee, [implant] positioning is very important because you want to be sure it fits right. Visibility is more important now than it’s ever been.”
So is bioabsorption and regeneration. For decades, scientists and clinicians have searched to no avail for an implant material that is just as good as natural bone. Innovations like synthetically-obtained Hydroxylapatite, poly N-isopropylacrylamide and bone morphogenic protein 2 show promise, but none hold the magic formula to a bioabsorbable substance that can retain a product’s structural and mechanical integrity.
Yet material experts continue to try. Last fall, Invibio unveiled a PEEK-Optima Hydroxyapatite-enhanced polymer designed to enhance bone growth on all sides of a device. A pre-clinical study using a sheep model showed the new material enhanced bone apposition within four weeks of implantation, and maintained apposition levels after 12 weeks.
MedShape Inc.’s new PEEK product—released in February—is manufactured with micrometer-scale surface porosity and based on Zeniva PEEK resin from Alpharetta, Ga.-based Solvay Specialty Polymers. PEEK Scoria uses a proprietary processing method that seamlessly connects a porous surface to a solid base. The structure maintains a shear strength twice that of trabecular bone while its surface features 65 percent porosity, a 300-micron average pore size and 99 percent interconnectivity.
While studies have shown the benefits of adding porosity in biomaterials to support tissue ingrowth around an implant, the use of porous polymers has been limited in orthopedic load-bearing applications due to a loss in mechanical properties. MedShape reportedly is the first company to develop and clear a porous PEEK device (the Morphix SP suture anchor) through the U.S. Food and Drug Administration.
Duke University researchers, meanwhile, are working to perfect the mix of synthetic scaffolding material with gene delivery techniques to create replacement cartilage. Investigators have found a way to genetically alter stem cells so they make necessary growth factor proteins on their own as opposed to traditional stem cell tissue repair, which requires deliveries of copious amounts of growth factor proteins once the developing material is in the body. The researchers incorporated viruses used to deliver gene therapy to the stem cells into a synthetic material that serves as a template for tissue growth. The resulting substance is like a computer—the scaffold provides the hardware and the virus provides software that programs stem cells to produce the desired tissue.
“One of the advantages of our method is getting rid of the growth factor delivery, which is expensive and unstable, and replacing it with scaffolding functionalized with the viral gene carrier,” assistant biomedical engineering professor Charles Gersbach said. “The virus-laden scaffolding could be mass-produced and just sitting in a clinic ready to go. We hope this gets us one step closer to a translatable product.”
* * *
T-minus 31 years and counting.
Humans have roughly three decades left to experiment with orthopedic implant materials before artificial intelligence perfects the process. Companies continue to rely on old favorites like titanium, stainless steel and polymers to craft the replacement joints and artificial discs that will likely sustain us until the moment of Singularity arrives. As one industry expert noted, “the innovation is not necessarily in the development of a new material, but in better understanding of what materials are already available, and applying existing materials more effectively.”
With the help of machines, of course.
At that point—in the Year of Singularity—computer intelligence will be roughly 1 billion times as powerful as the sum of all human intellect. Mankind’s reign on planet Earth will be over, prompting a societal transformation that Kurzweil calls “a singular change in human history.”
This is the way the world ends
This is the way the world ends
This is the way the world ends
Not with a bang but a whimper.
This is the way the world ends
This is the way the world ends
Not with a bang but a whimper.
— T.S. Eliot, “The Hollow Men,” 1925.
Or, the press of the “delete” key.
Or, maybe it doesn’t end at all. Kurzweil is confident that artificial intelligence dramatically will improve and eventually help extend the human experience. Expert systems will eradicate viruses through rapid DNA sequencing; they’ll create new body parts (already occurring through 3-D printing); and perhaps most impressively, they’ll reprogram the body’s “stone-age software” to halt the aging process, allowing man to achieve his ultimate dream of immortality. In Kurzweil’s future world, humans will be able to sprint for 15 minutes without taking a breath or go scuba diving with no gear. He also expects nanotechnology to significantly enhance our mental capabilities, and virtual reality to become a ubiquitous daily experience.
“We’re going to become increasingly non-biological to the point where the non-biological part dominates and the biological part is not important anymore,” Kurzweil said during last year’s Global Future 2045 International Congress. “In fact, the non-biological part—the machine part—will be so powerful it can completely model and understand the biological part. So even if that biological part went away it wouldn’t make any difference. We’ll also have non-biological bodies—we can create bodies with nanotechnology, we can create virtual bodies and virtual reality in which the virtual reality will be as realistic as the actual reality. I think we’ll have a choice of bodies…we’ll have different ways we can create bodies.”
Full-body construction is still a bit too advanced for the human brain’s 100 billion neurons (though exoskeletons and the walking, talking 6-foot-tall bionic robot currently housed at the Smithsonian Museum arguably measure up—in a rudimentary, pre-Singularity kind of way). Nevertheless, the cerebral cortex has become quite adept through the centuries at creating body parts: Ancient Egyptians crafted jawbone implants from ivory while the Maya preferred shells (their calcium carbonate purportedly integrated well with bone). The Romans’ proclivity for gold cranium implants was mimicked several millennia later by the Incas of Peru, although the doomed society also liked silver for skull repairs.
Twentieth-century advances in biomaterial science have created more superior body parts and biologically worthy substances. Most joint replacements, for example, are made of a stainless steel, zirconium, titanium, polyethylene and in certain cases, ceramic mix; prosthetic limbs are comprised of a carbon-fiber composite/polypropylene or polyethylene blend; artificial ears are made from silicone or spider silk, and some cranial implants consist of ultra high-performance polyetherketoneketone (PEKK).
Twenty-first-century innovations have expanded the list of medical materials well beyond the traditional metals and polymers to include diamond (retinal implants), lutetium oxyorthosilicate (X-ray imaging), gold (diagnostics), shrimp shells/silk (sutures, biological scaffolds) and glass (bone repair). Such options, however, are off-limits in the orthopedic sector, where manufacturers remain staunchly loyal to reliable veterans like PEKK, polyethylene, stainless steel, cobalt chromium and titanium, an overall favorite.
“Titanium continues to be the metal of choice for the major [orthopedic] OEMs—DePuy (Synthes), Medtronic, Biomet, Wright and Zimmer. We have no doubt they all are working with other materials, but titanium properties lend themselves very nicely to implants,” noted David Yoho, senior vice president at Vulcanium Metals International LLC, a global distributor of titanium mill products for various industries, including medical. “Titanium is lightweight, it’s strong and it’s biocompatible, that’s why the implant manufacturers love it. The material is used for nearly any type of implant you can think of—hip, knees, spinal, maxillofacial, pacemakers. It’s a wonderful material.”
So wonderful, in fact, that it often trumps other substances. Whether in natural form or chemically modified, titanium is used literally from head to toe in the human body, connecting joints, reinforcing bones, restoring vision, detecting sound waves and fusing vertebrae. Most, if not all, orthopedic OEMs sell titanium hips and/or knees, bone screws, nails, plates and cervical cages (Wright Medical Technology Inc. is the sole exception, though the company offers a line of thumb and hand/wrist implants).
Zimmer Holdings Inc. was an early Ti-6Al-4V convert, developing a “Natural Knee” System in 1985 that featured a cancellous-structured titanium porous coating option for better fixation. Executives claim the Knee—implanted in more than 400,000 patients globally since its introduction—was one of the first to replicate the human anatomy by duplicating the tibia’s asymmetrical shape.
Many of Zimmer’s rivals have followed suit over the years with their own attempts to mimic Mother Nature’s handiwork: Stryker Corp.’s Triathlon Total Knee Replacement System features shorter posterior condyles and a geometry designed to enhance the implant’s contact area, providing recipients with a natural knee rotation through 150+ degrees of flexion, while the Gription Titanium Foam implants from DePuy Synthes are tailored for patients missing bone in the tibial or femoral areas (the material—a porous structure made from commercially pure titanium—reportedly has a similar elasticity to bone and a coefficient of friction that allows for initial scratch fit).
“Everyone is trying to differentiate themselves from their competitors. We’re seeing more and more customers calling for specific chemical and physical properties in their materials—either higher or lower tensile strength, custom tolerances…it really depends on the application,” Yoho told Orthopedic Design & Technology. “If it’s a spinal implant or some type of trauma plate, you’re going to want specific [material] properties to make it perform as intended. If it’s a joint implant, you’ll want the material to be wear resistant and give maximum range of motion. There are various types of physical and chemical properties that may be required, and certain materials are better suited for certain applications. There are new [material] products coming out, but if it’s not titanium, there’s not a lot of conversation or buzz about it.”
There’s good reason for that buzz: Ti-6Al-4V is lightweight, strong, and impervious to the body’s corrosive bath of extracellular tissue fluid. The material also is more flexible than other metals and can withstand the incredible loads/stresses placed upon the lower joints. In addition, the non-ferrous element is compatible with magnetic resonance imaging and computed tomography scans.
Augmenting titanium’s mass appeal in recent years was the development of aluminum and vanadium-free grades (both metals have been linked to Alzheimer’s disease, neuropathy and ostemomalacia) as well as brands with antibacterial coatings. The metal could become even more popular in the future if researchers can improve its integration to living bone.
Clinicians in China and Japan may be close—they currently are experimenting with a urease fabrication process for coating titanium implants with bioactive calcium phosphate (CaP)/gelatin composites. The analysts implanted tiny 2-by-10-millimeter CaP/gelatin/titanium and CaP/titanium rods into the thigh bones of rabbits, using pure titanium rods as controls. Four and eight weeks after the surgery, the researchers noticed considerably more new bone on the surface of the composite CaP/gelatin/titanium rods than in the other two groups. Moreover, the CaP/gelatin/titanium rods bonded to the surrounding bone directly, with no intervening soft tissue layer, according to Science and Technology of Advanced Materials.
The results suggest that CaP/gelatin/titanium implants made from the researchers’ urease process not only can enhance the proliferation of stem cells and differentiation of bone cells, but also the bone bonding ability of the implant itself. “Such CaP/gel functionalized Ti might have great potential in joint replacements or dental implants,” the study authors wrote.
Pollyannaish on Polymers
While it remains a popular choice among orthopedic device manufacturers, titanium is far from a perfect implant material. For starters, it has poor shear strength, making it an inferior option for bone screws, rods, plates and similar applications (implant makers obviously disagree). The material also is prone to notching when it is bent or attached to pedicle screws, thereby increasing its proclivity to fatigue failure.
Perhaps more importantly, though, titanium tends to wear significantly when it is rubbed between itself or other metals, resulting in potentially harmful debris that can cause pain and loosen implants. Studies have shown titanium femoral heads wear substantially more than their cobalt-chrome-molybdenum (Co-Cr-Mo) and 316L stainless steel counterparts, averaging 74.3 percent degradation against high molecular weight polyethylene acetabular components (Co-Cr-Mo femoral heads produced the least amount of wear debris, according to research data). Clinical trials have reached similar conclusions, finding higher metal concentrations in tissue surrounding titanium prostheses than Co-Cr-Mo or stainless steel implants.
“There are precious few materials in orthopedics,” said Scott DeFelice, president and CEO of Oxford Performance Materials, a South Windsor, Conn.-based developer of ultra-high performance thermoplastic biomedical polymers. “Titanium has been the material of choice for a lot of reasons—predominantly for its biocompatibility, which is pretty well known. But it has a couple of things working against it. The biggest disadvantage is that titanium is stiffer than bone. The more conformal an [orthopedic] implant is to the bone, the longer its life will be and the healthier the bone will be. We’re now starting to see a generation of revision hip surgeries that is being driven by many factors, but quite often these surgeries are due to the material being too robust. It’s entirely appropriate given the stake of the science, but the industry is beginning to move toward material options that are more biochemically compatible with the body.”
Many of those options involve plastics like PEKK, polyetheretherketone (PEEK), polycaprolactone, polylactide (PLA), polyglycolide (PGA) and PLA-PGA combinations. DeFelice’s firm makes a 3-D printed cranial implant from PEKK, an osteoconductive material with similar mechanical properties as bone and twice the compressive strength of its sister ketone polymer, PEEK. The semi-crystalline thermoplastic siblings are quickly gaining ground on their metallic rivals, charming manufacturers with their high heat and chemical resistance, as well as their ability to withstand high mechanical loads.
PEEK’s allure intensified last summer after a seven-year-long clinical study determined the material is better than titanium at maintaining intervertebral height and cervical lordosis in the surgical treatment of cervical spondylotic myelopathy (CSM). A research team from Changzhen Hospital in Shanghai, China, designed the study to compare the outcomes of titanium and PEEK cages and discovered the titanium cage group demonstrated “significantly inferior outcomes” compared with the PEEK group.
Though it received little attention, the study reinforced PEEK’s capabilities as a viable orthopedic implant. Pioneered in 1999 by United Kingdom-based Invibio Biomaterial Solutions, implantable PEEK polymers have been developed in various formulations, ranging from unfilled grades with varying molecular weight to image-contrast and carbon fiber-reinforced versions (the latter helps eliminate environmental stress cracking, experts claim). The image-contrast class can contain metal wires (markers) or barium sulfate power to make them visible in X-rays.
“There’s been more of a calling for that kind of material,” said Mike Feld, sales development manager for Interstate Plastics, a multi-branch industrial plastics distributor and manufacturer headquartered in Sacramento, Calif. “Plastics are transparent under X-rays but with an additive they become visible. Sometimes you need the implant to be visible to be sure it is in the right place. Arthroscopy is more popular than ever…nobody is making a big cut anymore to go into the body. It’s all done through pinholes with cameras. When you’re not opening up the knee, [implant] positioning is very important because you want to be sure it fits right. Visibility is more important now than it’s ever been.”
So is bioabsorption and regeneration. For decades, scientists and clinicians have searched to no avail for an implant material that is just as good as natural bone. Innovations like synthetically-obtained Hydroxylapatite, poly N-isopropylacrylamide and bone morphogenic protein 2 show promise, but none hold the magic formula to a bioabsorbable substance that can retain a product’s structural and mechanical integrity.
Yet material experts continue to try. Last fall, Invibio unveiled a PEEK-Optima Hydroxyapatite-enhanced polymer designed to enhance bone growth on all sides of a device. A pre-clinical study using a sheep model showed the new material enhanced bone apposition within four weeks of implantation, and maintained apposition levels after 12 weeks.
MedShape Inc.’s new PEEK product—released in February—is manufactured with micrometer-scale surface porosity and based on Zeniva PEEK resin from Alpharetta, Ga.-based Solvay Specialty Polymers. PEEK Scoria uses a proprietary processing method that seamlessly connects a porous surface to a solid base. The structure maintains a shear strength twice that of trabecular bone while its surface features 65 percent porosity, a 300-micron average pore size and 99 percent interconnectivity.
While studies have shown the benefits of adding porosity in biomaterials to support tissue ingrowth around an implant, the use of porous polymers has been limited in orthopedic load-bearing applications due to a loss in mechanical properties. MedShape reportedly is the first company to develop and clear a porous PEEK device (the Morphix SP suture anchor) through the U.S. Food and Drug Administration.
Duke University researchers, meanwhile, are working to perfect the mix of synthetic scaffolding material with gene delivery techniques to create replacement cartilage. Investigators have found a way to genetically alter stem cells so they make necessary growth factor proteins on their own as opposed to traditional stem cell tissue repair, which requires deliveries of copious amounts of growth factor proteins once the developing material is in the body. The researchers incorporated viruses used to deliver gene therapy to the stem cells into a synthetic material that serves as a template for tissue growth. The resulting substance is like a computer—the scaffold provides the hardware and the virus provides software that programs stem cells to produce the desired tissue.
“One of the advantages of our method is getting rid of the growth factor delivery, which is expensive and unstable, and replacing it with scaffolding functionalized with the viral gene carrier,” assistant biomedical engineering professor Charles Gersbach said. “The virus-laden scaffolding could be mass-produced and just sitting in a clinic ready to go. We hope this gets us one step closer to a translatable product.”
* * *
T-minus 31 years and counting.
Humans have roughly three decades left to experiment with orthopedic implant materials before artificial intelligence perfects the process. Companies continue to rely on old favorites like titanium, stainless steel and polymers to craft the replacement joints and artificial discs that will likely sustain us until the moment of Singularity arrives. As one industry expert noted, “the innovation is not necessarily in the development of a new material, but in better understanding of what materials are already available, and applying existing materials more effectively.”
With the help of machines, of course.
3-D Printing: Boon or Burden for Medtech Manufacturing? Stephen Power has no memory of the 2012 motorcycle crash that disfigured his face. “I can’t remember the accident,” he told Britain's Daily Telegraph in March. “I remember five minutes before and then waking up in the hospital a few months later.” Power awoke to an unrecognizable reflection—a monstrous muddle of bulges, bruises and breaches from a badly-mangled leg and fractures to his cheekbones, skull, nose, and top jaw. Maxillofacial specialists in Wales successfully rebuilt most of Power’s face but a serious eye injury forced them to keep their distance from the 29-year-old’s shattered left cheekbone and eye socket. “As a result we did not get his left cheekbone in the right place and we did not even try to reconstruct the very thin bones around his eye socket,” consulting surgeon Adrian Sugar explained to the Telegraph. “So the result was that his cheekbone was too far out and his eye was sunk in and dropped.” Power masked the imbalance with bulky hats and glasses while doctors devised a plan to restore symmetry to his misshapen face. They achieved their goal through additive manufacturing, or 3-D printing, a rapidly developing manufacturing technology that creates physical objects by adding material in layers (hence the “additive” idiom). The process is converse to traditional “subtractive” manufacturing, where objects are made by cutting or machining raw materials into desired shapes. 3-D printing has been used in recent years to build an eclectic assortment of products—from a plastic (working) gun and tilt-shift camera lens to toys, guitars, clothes, even food (The Hershey Co. wants to incorporate the technology into its chocolate-making process—the blasphemy!—while NASA is spending $125,000 to develop a pizza printer). Yet none of those applications match the promise or confoundment of 3-D printed body parts and medical devices. Over the last several years, additive manufacturing has gained a solid foothold in the medtech sector, breeding experimental body parts, including bone. Orthopedists have exploited the technology to fabricate cutting and positioning guides, metal bone plates (Power’s face, for instance, is held together with titanium plates), and on occasion, plastic models for difficult-to-visualize fractures/deformities. “3-D printing allows you to make a device that is patient-specific…an implant that truly fits the individual,” explained Scott DeFelice, president and CEO of South Windsor, Conn.-based Oxford Performance Materials, manufacturer/printer of a customized polyetherketoneketone cranial implant (OsteoFab). “The [printed] part is perfectly matched to the particular defect and shape of the patient’s anatomy. That’s something you really can’t do with conventional manufacturing methods, either for economical or technological reasons.” Customization, however, is just one of the many shortcomings of traditional manufacturing, a complicated and potentially time-consuming process that generally requires costly molding machines and complex tooling to produce vast quantities of goods. Outsourcing—while practical in many cases—can muddle the process, forcing companies to overcome geographical and cultural barriers to develop and deliver their products. 3-D printing, by contrast, eliminates the need for outsourcing as well as the bulky multi-axis milling machines used by many medtech OEMs in their production facilities. And, since items can be made relatively quickly, lead times are significantly reduced. With its evolution still underway, it seems a bit premature to deem 3-D printing a “second industrial revolution.” Nevertheless, as the technology becomes faster, cheaper and more sophisticated, it surely will have wide-reaching impacts on the medtech industry. “The impact could be huge, especially on the contract manufacturing side,” noted David L. Smith, vice president of business development for Boston Centerless, a Woburn, Mass., supplier of precision ground bare materials and grinding services. “People that use certain technology to form parts today are very heavily invested in screw machines, multi-axis milling machines, turning centers, molding machines, casting and so on. The whole industry is looking over its shoulder, concerned about whether a guy in an office with a 3-D printer can obsolesce all this equipment just by printing out a part—and printing that part not in a clean room, but in a regular environment.” The industry needn’t be too concerned: 3-D printing still has some major obstacles to clear before it can ever attempt to antiquate traditional manufacturing methods (even then, experts doubt it would succeed). Matching its rival’s economies of scale currently is one of the technology’s most pressing challenges, as is the limited selection of printable materials. Smith, though, believes the deciding factor will reside with product quality. “The question is, can you produce components using 3-D printing and still get the physical characteristics in the material to meet the needs of the intended application?” he asked. “A 3-D printed component is basically a casting—in the case of metal, you’re melting microscopic sections and allowing it to consolidate in a very ordered way. It’s a melted and solidified structure. The types of materials we work with have been casted, but they’ve been hot rolled and forged and modified in a hot state that causes the microstructure in many cases to be much stronger than it would in casting. You can 3-D print a lot of different shapes and components but will they have the mechanical characteristics they need to perform in their intended applications?” Maybe not, but they certainly could produce some interesting objects. “If we can control the crystalline structure of metals,” mused Jarrod Bassan, senior consultant at IT/professional services provider Computer Science Corporation, “just imagine some of the properties we could imbue to a metal part that’s hard and brittle at one end but springy and soft at the other end.” The possibilities truly are endless. — M.B. (Editor's note: For more on 3-D printing, turn to page 30.) |