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Back in the Game
Patient demand for high function and
near-perfect fit continues to drive
innovation in orthopedic implants and
surgical procedures.
Michael Barbella • Managing Editor
J
ay Cutler officially entered the World of the Absurd at 3:02 p.m.
on Tuesday, Nov. 29, 2011, barely a week after the starting
Chicago Bears quarterback fractured his right thumb during a
31-20 victory over the San Diego Chargers.
On that day, at that precise time, Cutler’s broken first digit took
to social media to confront its owner. The sassy finger, perhaps
irritable from its injury, tweeted to the veteran passer:“The cast is
HUGE! btw how u doin?”
Clearly not amused, Cutler fired back,“Less talking out of you
and more rehab! Go find some ice or something.”
Showing its humorous side, the finger later asked (to no
response, of course),“Thumb war anyone? O wait...”
At one point that afternoon (the obvious apex of the day’s digital lunacy), multiple Twitter accounts that claimed to be Cutler’s
thumb had surfaced, slinging insults and accusing others of being
the veteran passer’s lesser-known left thumb. By the end of the
day, @jaycutlerthumb (the injured finger) was sparring openly
with @JayCutlersThumb, an entity that—judging by the tweets—
can best be described as a slightly more cantankerous digit.
Certainly, the tweets were a surprising change from an athlete
better known for his abrasive demeanor and lack of charm than
his sense of humor. In hindsight, the banter most likely was Cutler’s coping mechanism at work, helping him come to terms with
the gravity of his season-ending injury. Consider the tweet he sent
on Thanksgiving Day to update followers and Bears fans about his
condition:“Surgery went great. Randy Viola is the best. My nurse
isn’t bad either @KristinCav ;) Be back as soon as I can.”
Cutler may have had eyes for his nurse (perhaps she resembled
his on-again, off-again MTV reality star girlfriend/fiancee Kristin
Cavallari), but it was Viola with whom the quarterback truly was
smitten.Viola, 45, is a hand, wrist and elbow specialist at The Steadman Clinic, a world-renowned orthopedic facility with offices inVail
and Frisco, Colo.Viola’s approach to orthopedic surgery is a bit unorthodox (he considers it“responsible yet aggressive”)—he tailors
implants to an athlete’s sport to help reduce healing time.
Viola’s fracture fixing game plan abandons tradition, trading
the typical bulky splints and stiff immobilization measures for
metal plates, screws and pins that set broken wrists or thumbs in
carefully calculated athletic positions.
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Photo courtesy of Triangle Manufacturing Co Inc.
For example, he’ll fit a sterile baseball into a pitcher’s hand during surgery and bend a finger to simulate a certain grip, or he’ll
meticulously position the wrist and thumb to help injured skiers
regain their grasps on poles.
To repair the break at the base of Cutler’s right thumb (known
in layman’s terms as a Bennett’s fracture), Viola inserted three
screws and two pins near the bottom of the first metacarpal. The
hardware eventually will be removed.
Viola’s unique fracture repair technique and the expertise of
his Steadman Clinic colleagues has made the 22-year-old facility
a haven for high-profile professional athletes such as Cutler hoping to minimize recovery times from serious injuries. The clinic’s
client list reads like an ESPN Wide World of Sports all-star roster:
New York Yankees third baseman Alex Rodriguez, New York
Giants defensive end Osi Umeyiora, Buffalo Bills quarterback Jack
Kemp, Denver Broncos quarterback John Elway, Minnesota
Timberwolves point guard Ricky Rubio, Los Angeles Lakers
shooting guard Kobe Bryant, Pittsburgh Penguins forward Mike
Comrie, golfer Greg Norman, tennis greats Martina Navratilova,
Billie Jean King and Lindsay Davenport, and top skiers Phil
Mahre, Picabo Street and Bode Miller.
“Most physicians look at it from a‘What should you do?’standpoint,” Viola, a medical consultant to the U.S. Ski Team, Colorado
Rockies and the Denver Broncos, told the ChicagoTribune in a rare interview late last year.“Athletes don’t look at things that way. They
want to know how they can push the limit. We give them the option
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of fixing things with hardware, which
provides support and takes away pain so
often it gets them back in the game a lot
faster. Some older, more classically trained
orthopedists would consider it aggressive,
but it’s becoming more common to fix
people with plates and screws and get them
back to competition as soon as possible.”
An expeditious return to competition—
whether it be an athletic contest or the perpetual struggle for economic security—has
influenced much of the innovation in
orthopedic implants in recent years. Patient
expectations, desires and needs have
evolved dramatically since British surgeon
Sir John Charnley devised the total hip
replacement nearly 50 years ago. Since the
debut of the RCH 1000 (the official name
of Charnley’s ultra-high molecular weight
polyethylene hip socket), patients have
come to expect more from their implants.
While pain relief remains the primary driver
of hip and knee replacement surgery, the
desire to maintain an active lifestyle or
work well beyond retirement age also have
become motivating factors. The possibility
of life without golf, for instance, prompted
63-year-old William Mills of Philadelphia,
Pa., to undergo a double knee replacement
in 2006. A similar desire led retired chemist
Edward Moore to replace his aging knee
three years ago after pain began limiting his
activity. His daughter had reservations
about the procedure but Moore never gave
it a second thought.
“I didn’t do much mulling about it,”he
told The NewYork Times in February.“It just
seemed like the knee would be hampering
me for the rest of my life, and that sounded
like a bad idea.”
Hardly anything hampers Moore now.
Having fully recovered from his knee
replacement surgery, the Woodbury, N.J.,
resident has resumed a full slate of activities. Last September, in fact, just two days
after turning 94, Moore took his wind
surfer to Lakes Bay, a top-ranked windsurfing site near Atlantic City, N.J.“I got up
on the board and I sailed,”he said.
Implant Material Evolution
The artificial joints that sustain the recreational hobbies of active nonagenarians
like Moore and baby boomers like Mills
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(he biked 250 miles through Germany a
mere six months after undergoing double
knee surgery) are the by-products of more
than half a century of research and development, materials testing, ingenuity, foresight, and trial and error.
Most of the early man-made hips and
knees were crude devices (at least by 21stcentury standards), designed specifically to
serve a sedentary elderly patient population. In 1891, German professor Themistocles Glück created an ivory ball and hip
socket that attached to the bone with
nickel-plated screws. Several decades later,
implant designers had migrated to steel or
chrome, and while those joints relieved
arthritis pain, they quickly wore down and
easily loosened, necessitating repeat surgeries. Teflon wasn’t much better—the material triggered bone tissue degeneration
(osteolysis) and wore out within two years.
Charnley’s hip design became the gold
standard in artificial joint replacement due
to its relatively low wear and femoral-acetabular component marriage of metal
(originally stainless steel) and ultrahigh molecular weight polyethylene
(UHMWPE), a biocompatible plastic with
excellent impact strength, a low coefficient
of friction and good fatigue resistance.
Gamma irradiation of UHMWPE implants
induces cross-linking and can improve
wear resistance but it also can lead to chain
scission and resulting oxidative degeneration, which can weaken the implant and
ultimately cause its failure.
For more than two decades, the Charnley
Low Friction Arthroplasty design was the
world’s most-used hip replacement system,
surpassing other available options like the
ivory hip prosthesis developed by Burmese
orthopedic surgeon San Baw, M.D., to replace ununited fractures of the femoral neck.
Though it was considered revolutionary
at the time, Charnley’s Low Friction design
contained a significant shortcoming—its
small femoral head (22.25 millimeters) produced considerable wear debris, which was
not an issue for the targeted couch potato
patient but a serious problem for active folks.
That shortcoming might have been
irrelevant to the evolution of implant design had future retirees remained as sedentary as their predecessors. But baby
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boomers—that throng of 79 million men and
women who spent part of their youth
marching in support of civil rights and
protesting the Vietnam War—refused to sit
still in their Golden Years. The boomers’
desire and determination to maintain their
mobility as they approached retirement represented a radical shift from tradition but it
also presented a golden opportunity to
orthopedic firms that could improve both the
quality and longevity of existing implants.
Such a demographic shift has resulted
in a bevy of new products over the last two
decades as companies developed materials and devices designed to withstand the
daily vigors of an active joint.
Invibio struck gold in the late 1990s
with the development of implantable polyetheretherketone (PEEK), an organic polymer thermoplastic that has become a
popular alternative to UHMWPE for its
strength, durability, lubricity, and X-ray
translucency as well as its biocompatibility
and biostability.
PEEK’s mechanical properties can be
tailored to meet a company’s specific requirements. For example, the material’s
strength and stiffness can be increased by
adding carbon fibers to the polymer matrix, thus enabling orthopedic device manufacturers to develop applications that
satisfy high-strength requirements. Invibio’s carbon fiber-reinforced (CFR) technology currently is used in the EnduRo
knee revision system developed by Aesculap Inc. for patients suffering from a failed
total knee arthroplasty. The system—approved by the U.S. Food and Drug Administration (FDA) in December 2010—is
designed to increase implant longevity and
minimize (or ideally eliminate) the need
for revision knee surgery, according to
Center Valley, Pa.-based Aesculap.
PEEK’s imaging properties also can be
tailored by adding various concentrations
of barium sulphate.The addition of this inorganic compound helps create a material
that easily can be inspected post operatively through traditional imaging techniques without the generation of scatter or
other imaging artifacts.
In addition to its mechanical and
adaptable properties, implantable-grade
PEEK can be processed through several
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methods, including injection molding, extrusion, compression molding, machining
from plates/rods and powder coating.
PEEK, however, has its limitations. One
of the major disadvantages of the material
is its inability to blend well with bone,
making it a difficult choice for orthopedic
applications that require osteointegration.
Over the last decade, orthopedic manufacturers have experimented with ceramics and various biologics to achieve optimal
bone ingrowth. Amedica Corporation, for
instance, has discovered the merits of silicon nitride (Si3N4), a strong, heat-resistant
material used in the automotive and aerospace industries. The Salt Lake City, Utahbased spinal and reconstructive implant
maker is incorporating the material in its
products due to its superior strength and
imaging characteristics.
“Your standard materials for both implants and instruments is the basic stainless steel, cobalt chrome, titanium, and
tantalum. And of course, ultra high molecular weight polyethylene lives with us
every day,” noted Tobias Buck, chairman
and CEO of Paragon Medical Inc., a Pierceton, Ind.-based Tier 1 supplier of cases,
trays, surgical instruments and implantable
components. “But ceramics is a material
that will truly change the way implants are
configured in the future and certainly the
way they are configured today.You’re dealing with aluminum oxide, there’s zirconium oxide, and what that is doing is
mitigating wear.You have some incredible
composite materials currently in the market that seek to make the implant more
stable, extend its life and better integrate
with the body.”
One of those innovative composites is
made by Ceramatec Inc., a Salt Lake firm
focusing on the research and development
of ceramic technologies. The company has
designed a porous, foam-like scaffold that
contains channels to allow bone ingrowth
and solid struts to support weight-bearing
loads. The scaffolds, according to Ceramatec, can be pre-infiltrated with hydroxyapatite, beta-tricalcium phosphate, bone
morphogenetic protein, collagen and
growth factors to maximize healing and
osteointegration. In addition, the pore
shape, size, aspect ratio, volume, channel
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spacing, alignment and interconnectivity
easily can be controlled with the scaffold.
Another groundbreaking implant composite could be added to the market later
this year by InVivo Therapeutics Holdings
Corp., which is awaiting Investigational
Device Exemption approval of its biocompatible polymer-based scaffolding. With
the FDA’s blessing, the Cambridge, Mass.based firm will begin testing its scaffolding
in patients with acute spinal cord injuries
(SCIs)—traumatic damage that results in
either a bruise (also called a contusion), a
partial tear, or a complete tear (a.k.a. transection) in the spinal cord. The open label
clinical study is designed to evaluate the
safety and efficacy of InVivo’s biopolymer
scaffolding treatment in 10 SCI patients.
The scaffolding treatment, according to
the company, provides structural support to
a damaged spinal cord in order to prevent
tissue scarring and improve both recovery
and prognosis after a traumatic SCI. InVivo
uses technology co-invented by Massachusetts Institute of Technology professor
Robert Langer, Sc.D. (a member of the company’s scientific advisory board) and Joseph
P. Vacanti, M.D., surgeon-in-chief and chief
of pediatric surgery at Massachusetts
General Hospital for Children in Boston.
InVivo’s scaffold device is made of polylactic-co-glycolic acid, a biodegradable,
biocompatible polymer that is used in surgical sutures, drug delivery devices and tissue engineering applications. The product
is designed to prevent cascading inflammation, scarring or secondary injuries
commonly associated with SCIs that often
lead to permanent paralysis.
The sponge-like scaffold generally is
about a centimeter in length, though its
size can vary depending on the SCI. Surgeons implant the scaffold directly into the
injury site, guided by images taken shortly
before the procedure and with ultrasound.
Beyond reducing inflammation and
helping to prevent secondary injury, the
scaffolding provides a matrix to promote
regrowth and reorganization of neurons
and neurites. The treatment also serves as
a “synthetic extracellular matrix” to promote the survival of surrounding neurons,
according to InVivo.
The scaffolding could be used with curodtmag.com
rently available fixation systems. It would
be completely absorbed by the body within
12 weeks.
Some of the most novel implant technologies involve cutting-edge orthobiologic
materials such as woven fabrics and cancellous bone. Amedica, the company using
silicon nitride in its implants (the same material used in the space shuttle), also
offers a product called Dynamic Bone, a
customized, compressed demineralized
cancellous bone that expands like a sponge
upon hydration. As an osteoconductive material, Dynamic Bone is ideally suited for
spinal fusion procedures, and can be hydrated with osteoinductive liquids such as
bone marrow aspirate, bone morphogenetic
proteins or other viable tissue matrix products. Amedica claims its Dynamic Bone
product is unique in its ability to continually
expand after it is placed within the vertebral
body, filling any open cavity for a custom
press-fit. Such a custom fit ultimately could
help improve overall spinal fusion rates.
Solvay Advanced Polymers LLC has
teamed up with Perkasie, Pa.-based Secant
Medical LLC to produce implantable biomedical fabric structures for therapeutic
devices in orthopedics, cardiovascular devices, tissue engineering, neurology and
general surgery. Secant uses Zeniva PEEK
resin from Solvay to produce the implants.
“We are working with [Secant] to talk
to customers about how to use a fabric in a
minimally invasive way and achieve different types of structural components,” said
Shawn Shorrock, global healthcare market
manager for Solvay Specialty Polymers, a
global provider of high-performance plastics.“It’s interesting for things like ligament
replacement but it’s also interesting for
things like annulus repair and different
kinds of shoulder repair. It’s a very unique
opportunity because this folded piece of
fabric that has a lot of structure to it can be
inserted it into place through a catheter via
a minimally invasive procedure. It expands
in-situ and you can fill it with bone cement, for example, or you can put some
additional component in there to give it
some structure but it can also be inserted
in a minimally invasive way. It really opens
up the opportunities and provides a whole
new way of looking at things.”
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Design Trends
Indeed, the opportunities are boundless for
innovative implant materials such as knitted fabrics and ceramic scaffolds. But there
still is room for improvement—failures and
limited lifespans are still a significant problem for manufacturers. Industry data suggest that roughly 17 percent of patients that
receive total joint replacements undergo
additional surgery due to device loosening
in the body. The failure rate of metal-onmetal hips is perhaps most disturbing: A
British study showed that 6.2 percent of patients with all-metal implants needed
corrective surgery, usually to replace the
device, within five years. It also confirmed
claims that women were more likely to
need revision surgeries, as are patients who
received their implants around 2004, when
many hips were redesigned to include a
larger head, or ball, of the joint. According
to researchers, the larger the joint head, the
earlier the all-metal hip device failed.
Attempts to curtail these failures have
spawned advancements in implant design
and instrumentation over the last several
decades. Patient-specific devices have become an increasingly popular way for
manufacturers to compensate for shortcomings in existing designs and accommodate joint deformities in patients. Most
orthopedic OEMs have developed patientspecific implants (PSI) as an alternative to
their traditional models, which come in
limited sizes and are based on measurements taken either from product literature
or a small sampling of patient data. Standard joint replacements generally do not
account for variations in mediolateral or
antero-posterior dimensions, nor do they
reflect the precise curvature of a bone canal
in specific patient populations. The lack of
such data during the design phase can impact an implant’s chances of failure within
the body, experts claim.
By more closely matching the implant
to the patient, manufacturers can increase
a new joint’s chances of success and minimize the need for revision surgeries.
“There’s a lot more discussion lately on
the implantable side with custom devices,
where manufacturers try to match the implant as close as possible to the original
anatomic structure of the patient,” noted
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Dax Strohmeyer, president of Upper Saddle River, N.J.-based Triangle Manufacturing Co. Inc., a company specializing in
precision engineering and manufacturing
of complex, tight-tolerance machined parts
and assemblies, including hip, knee, shoulder and spinal implants.
Robotic systems have been developed
in recent years to better fit hip and knee
implants to patients.The robot uses an end
mill to machine the bone to fit the implant,
and the tool path is generated based on a
computed tomography-derived computer
aided design (CAD) model of the joint and
a CAD model of the implant. Studies have
proven that robots can achieve a more precise cutting operation than the average orthopedic surgeon can achieve using hand
tools and cutting guides. One study
showed the average contact surface between the bone and the implant to be only
50 percent when using conventional methods—an insufficient level to ensure prompt
and secure fixation. Robots, on the other
hand, can achieve an average bone-implant contact surface of 95 percent, which
reduces the fixation time and improves the
initial stability of the implant. A robot is capable of performing cutting operations of
complex freeform surfaces and is not limited to planar cuts, as is the case when
using conventional cutting methods.
Perhaps to better compete with the robots (or to spite them), OEM implant manufacturers are designing smaller devices,
components and instruments that can be
used in minimally invasive surgery to replace the smaller joints of the hand, wrist,
elbow and ankle. Symmetry Medical Inc.
President and CEO Thomas J. Sullivan said
he has noticed more demand for instruments that improve visibility and access.
Based in Warsaw, Ind., Symmetry supplies
implants, instruments and cases to orthopedic device manufacturers.
“We are seeing interest from our OEM
customers and their surgeons for instrumentation that enables better visibility and
access through smaller incisions,”Sullivan
told Orthopedic Design & Technology. “We
know in the past the incision was much
larger than it is today. The trend toward
more minimally invasive has continued
with customers looking to minimize tissue
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disruption to speed recovery and yet still
have the same great outcome. To achieve
that goal, we see a need to complement
the smaller incision with proper retraction
for access, instruments that are sized and
ergonomic to enable you to move effectively within the joint cavity, and of course
visibility for exposure and alignment.
Without all three, simply a smaller incision
might be to the sacrifice of the historically
excellent long term clinical outcome.”
The demand for smaller, more complex
shapes and components has forced many
companies to become adept at micromolding. Spectrum Plastics Group executives are investigating the viability of
providing “one-off” services to customers
(the ability to make just one copy of
something). Such a service, however,
could be costly, said Mark D. Schaefer,
corporate vice president of business development for the Minneapolis, Minn.based provider of rapid prototyping,
additive manufacturing, quick-turn tooling and molding, injection molding of
thermoplastic and liquid silicone rubber,
and contract manufacturing services.
“If we were to build an injection mold
and make one part, the lead time, even
with our FastTrack tool building capability,
would be too long and cost per part would
be astronomical,”Schaefer explained.
“However, with additive manufacturing
processes and a CAD file you can make
one piece out of PEEK. It is a technology
that we are investigating because we also
do laser sintering of nylon. However, this
would be a major capital investment requiring totally new equipment to do it in
PEEK. The market is in its infancy.”
Cost: The Ultimate Challenge
The challenge posed by smaller orthopedic implants and components is easily conquerable compared with the more complex
mix of increasingly stringent regulatory requirements and pricing pressure. Contract
manufacturers, suppliers and OEMs are
under perpetual pressure to reduce costs to
compensate for shrinking reimbursement
rates and increased competition from a
globalized market.
Over the next four years, the United
States is expected to add millions of people
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to the Medicare-eligible pool, a population
that often seeks orthopedic care. However,
Medicare reimbursements for treatment
seldom covers the cost of care, which gives
surgeons few options other than restricting access to elderly patients or absorbing
a loss on services provided.
Compounding these pressures are
more rigorous FDA requirements for
quality assurance and basic tasks,
including documentation and inspection
reporting, process validation and compliance with ISO 13485 standards, industry
experts said.
“FDA regulations placed on our customers continue to raise the bar to manufacture orthopedic implants,”noted Sarah
Stanley, business development manager
for Tegra Medical, a contract manufacturer
and assembly services provider based in
Franklin, Mass.“We are experiencing more
rigorous requirements with equipment validations, special process validations, capability analysis, risk analysis, control plans
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and measurement systems analysis. We are
hearing from customers that the FDA
could soon require implants to be laser
marked with a serialized lot number. We
have a few customers that have already
changed their requirements to include serialized lot numbers on all implants that
we manufacture.”
* * *
For more than a century, orthopedic implant manufacturers and design engineers
have tried their best to create the perfect
implant. They’ve experimented with various materials—ivory, metal, titanium, tantalum, ceramic, glass, even plaster of
paris—and designs only to discover that
perfection exists only in nature. Attempts
to achieve the near impossible (and more
importantly, prevent implant failure) nevertheless have continued with the development of patient-specific devices and
joint replacement components that are
smaller, more complex and can be inserted
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through minimally invasive procedures. As
the industry marks a half century since the
debut of the “modern” hip implant, research continues into innovative substances that might one day lead to
everlasting man-made joints. For such a
breakthrough to occur, though, experts
claim the industry must resolve the paradox created by increasing regulatory requirements and the enormous pressure to
reduce manufacturing costs. As Paragon
Medical’s Buck observed:“There’s an interesting paradox that exists in this industry.
How can you have the amplification of
regulatory requirements across the
board—which are very restrictive and
amplify costs—in the face of extreme
downward price pressure? How can those
two things co-exist? The pendulum has to
swing back to the middle on the application of regulatory doctrine so there is a
greater level of sanity in the manufacturing space.” That may prove to be more
elusive than the perfect implant.
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