An Inside Look
Turn on the TV and there is golf legend Jack
Nicklaus extolling the virtues of his hip replacement. Still
competing on the links, Nicklaus is among the growing number
of people in the United States each year who have a hip
joint replaced. So is rock star Eddie Van Halen, who was
43 when he had his hip replaced in 1999, the same year as
Cases like these are laying to rest the stereotype
that only the aged and the inactive receive hip replacements.
The same holds true for those who have knee joints replaced.
The American Academy of Orthopaedic Surgeons
(AAOS) calls total hip replacement an orthopedic success
story, "enabling hundreds of thousands of people to live
fuller, more active lives." In 2001, about 165,000 hip joints
were replaced in U.S. hospitals, according to the National
Center for Health Statistics. The same year, 326,000 knees
were replaced. Total knee replacement is "highly successful
in relieving pain and restoring joint function," says the
AAOS. And a hip or knee replacement lasts at least 20 years
in about 80 percent of those who get them.
But despite their success, hip and knee joint
replacements still have drawbacks. There may be complications.
They don't always last a lifetime and when they fail, surgery
may be needed.
As artificial joints and surgical techniques
to implant them continue to evolve, the medical community
and patients hold out hope for joint replacements that cause
fewer problems, last longer, and move more like a healthy
What is Joint Replacement?
Joints are formed by the ends of two or more
bones connected by tissue called cartilage. Healthy cartilage
serves as a protective cushion, allowing smooth, low-friction
movement of the joint. If the cartilage becomes damaged
by disease or injury, the tissues around the joint become
inflamed, causing pain. With time, the cartilage wears away,
allowing the rough edges of bone to rub against each other,
causing more pain.
When only some of the joint is damaged, a
surgeon may be able to repair or replace just the damaged
parts. When the entire joint is damaged, a total joint replacement
is done. To replace a total hip or knee joint, a surgeon
removes the diseased or damaged parts and inserts artificial
parts, called prostheses or implants. These prostheses are
considered medical devices, which are regulated by the Food
and Drug Administration.
Why Joint Replacement?
The most common reason for having a hip or
knee replaced is osteoarthritis, according to the National
Institute of Arthritis and Musculoskeletal and Skin Diseases
(NIAMS). This degenerative joint disease, marked by the
breakdown of the joint's cartilage, is not limited to older
people. Although it most commonly affects people over age
45, younger men and women also can get this disease.
Some people are born with a deformed joint
or defective cartilage, which leads to osteoarthritis. Excess
weight, joint fracture, ligament tears, or other injury
can damage cartilage and cause osteoarthritis.
Rheumatoid arthritis is another condition
that may be alleviated by hip or knee joint replacement.
This chronic inflammation of the joint lining causes pain,
stiffness, and swelling. The inflamed lining can invade
and damage bone and cartilage. Rheumatoid arthritis generally
starts in middle age, but can also affect children and young
Loss of bone caused by poor blood supply
(avascular necrosis), which led to Van Halen's hip replacement,
and bone tumors may be other reasons for joint replacement.
Hip Replacement Surgery
The hip joint is a ball and socket, allowing
a wide range of motion. The ball of the joint, the top of
the thighbone (femoral head), moves within the hollow socket
(acetabulum) of the pelvis. A layer of cartilage allows
the ball to glide smoothly inside the socket.
In total hip replacement, the surgeon cuts
away the ball part of the joint, replacing it with a ball
attached to a stem that is wedged into a hollowed-out space
in the thighbone. Damaged cartilage and bone are removed
from the socket and a cup-like component is inserted into
Hip replacements may be cemented or uncemented.
If cemented, the hip parts are held in place with a fast-curing
"bone cement" made from a type of polymer. If uncemented,
the joint components are specially made to either press
into the bone for a tight fit (press-fit) or to allow new
bone to grow into the porous surface of the implant, holding
it in place (biological fixation).
An alternative to total hip replacement is
an operation called hip resurfacing. Unlike the prostheses
used in total hip replacement, which are made to replace
the femoral head, resurfacing prosthesis designs allow the
head to be preserved and reshaped. The resurfaced bone is
then capped with a metal prosthesis. Like total hip replacement,
the socket is fitted with a prosthesis.
In the United States, hip resurfacing is being
conducted only in FDA-approved clinical studies. It is necessary
for each manufacturer of a hip resurfacing device to collect
clinical data on its resurfacing design. The data collected
in these studies will be used to demonstrate whether each
hip resurfacing design is safe and effective for market
approval in the United States. Presently, no manufacturer
has obtained FDA approval to market its hip resurfacing
Not everyone is a candidate for resurfacing;
the femoral head may be too damaged to hold the resurfacing
component. "Good bone stock is required," says Michael Mont,
M.D., director of the Center for Joint Preservation and
Reconstruction at Sinai Hospital in Baltimore.
James Puglisi considers himself fortunate
to have good bone stock. Puglisi was 47 when he began limping
because of a burning, aching pain in his hip that spread
through his leg and into his knee and ankle. For this marathon
runner and cyclist, just walking and standing became painful,
and sometimes the pain was so intense that it would wake
him up during the night.
Puglisi was diagnosed with osteoarthritis,
brought on by an abnormally formed hip joint. He was advised
by his orthopedic surgeon to wait as long as possible before
getting a total hip replacement because it might wear out
with his active lifestyle and require one or more revisions.
Revision surgery, which replaces both artificial
parts and damaged bone, is more difficult than first-time
surgery, says NIAMS. The outcome is generally not as good
because bone is not as strong as when first operated on
and the supporting ligaments may be damaged.
"But the pain was getting to the point where
I needed to do something," says Puglisi.
Puglisi flew from his home in Amherst, N.Y.,
to Baltimore to take part in a study on hip resurfacing.
Mont performed Puglisi's resurfacing operation in March
2003 and Puglisi returned home after a four-day stay at
Sinai Hospital. Gradually putting more weight on his new
hip, Puglisi was able to be full weight-bearing (walking
without a cane or crutches) after three months. Now pain-free,
the 50-year-old is back to cycling 200 miles a week and
anticipates running again soon. "I'm so happy with the results,"
he says. "I had forgotten what it was like to have a pain-free
life, and now I have it back. It feels as normal as my other
Puglisi notes that different surgeons may
have different recommendations. Another surgeon who saw
Puglisi's X-rays told him he shouldn't run again. "But Dr.
Mont was OK with it as long as I waited at least six months
after surgery," says Puglisi. "He just told me I couldn't
bungee jump or parachute!"
Mont advises the six-month waiting period
to give a patient time to build strong muscles. He also
says he doesn't "totally condone heavy sporting activities"
after resurfacing. "You do it at your own risk," he says,
adding that if the resurfaced hip ever fails, it can be
converted to a total hip replacement.
Current hip resurfacing technology is too
new to know how long the resurfaced hip will last. Puglisi
has volunteered to return to Sinai Hospital for an annual
checkup for the next 10 years to help clinical investigators
gather long-term data on resurfaced hips.
Knee Replacement Surgery
The largest joint in the body, the knee joint
is formed where the lower part of the thighbone (femur)
joins the upper part of the shinbone (tibia) and the kneecap
(patella). Shock-absorbing cartilage covers the surfaces
where these three bones touch.
In a standard total knee replacement, the
damaged areas of the thighbone, shinbone and kneecap are
removed and replaced with prostheses. The ends of the remaining
bones are smoothed and reshaped to accommodate the prostheses.
Pieces of the artificial knee are typically held in place
with bone cement.
A knee replacement usually involves three
to four days in the hospital. The recovery period depends
on a patient's general health, age, and other factors, but
many people can resume their normal activities four to eight
weeks after surgery.
"While a knee replacement can dramatically
improve the quality of life for a person with debilitating
knee pain, it is major surgery," says Gerard Engh, M.D.,
director of knee research at Anderson Orthopaedic Research
Institute in Alexandria, Va. "We usually recommend total
knee replacements and partial knee replacements after other
less invasive treatments have been attempted."
But most who opt for knee joint replacement
are generally happy with the results. Ninety percent of
those who have total knee replacement report fast pain relief,
improved mobility, and better quality of life, according
to a panel of independent experts. The panel was convened
at a conference in December 2003 sponsored by the National
Institutes of Health (NIH) and cosponsored by the FDA and
other federal organizations.
The panel concluded that, overall, total knee
replacement surgery is a safe, very successful, and relatively
low-risk treatment for decreasing pain and increasing mobility
in people who are not helped by nonsurgical treatments.
Follow-up studies showed that revision surgery was needed
in 10 percent of knee replacements after 10 years, and in
20 percent after 20 years, according to the panel.
Where the FDA Fits In
Artificial joints are medical devices, which
must be cleared or approved by the FDA before they can be
marketed in the United States. In addition, FDA permission
is required before a company can test a new or redesigned
prosthesis in human studies. The data gathered in these
studies, which take place in specific hospitals, may then
be used to support a company's application for marketing
its prosthesis to surgeons and hospitals throughout the
What does the agency look for before clearing
a prosthesis for marketing? "It has to be proven safe and
effective," says Barbara Zimmerman, chief of the FDA's orthopedic
devices branch. "FDA assures safety and effectiveness using
different means depending on the risks of a particular device
and the technology that it presents."
For devices with a history of safe and effective
use, frequently those using established technology, the
FDA relies on a set of general controls to determine which
devices can be marketed, says Zimmerman. "These general
controls are augmented with special controls such as standards
or standard test methods.
"For devices involving new uses or advanced
technology, FDA often requires that a particular device
be demonstrated to be safe and effective through clinical
trials," she says.
The Risks of Replacement
Like any surgery, hip and knee joint replacement
carries certain life-threatening risks, such as infection,
blood clots and complications from anesthesia. Other complications
include nerve damage, dislocation or breakage after surgery,
and wearing out or loosening of the joint over time. After
hip replacement surgery, one leg may be shorter than the
Infection is an ongoing risk for people with
joint replacements. Not only can it occur in the hospital,
but it can happen years later if bacteria travel through
the bloodstream to the replacement area.
In the rare case that an infection spreads
to the new joint and does not clear up with antibiotic treatment,
the joint must be replaced. This usually requires two surgeries--one
to remove the infected joint and another surgery later to
insert the new joint. Between surgeries, the infection is
treated with antibiotics.
In 2001, the FDA approved a temporary artificial
hip for people with hip joint infection. The temporary hip,
called Prostalac, can be inserted and left in place for
about three months after the infected hip is removed. It
consists of a metal stem and ball that fits into the thighbone,
a plastic cup that attaches to the hipbone, and a bone cement
that contains antibiotics. The antibiotics in the cement,
along with oral antibiotics taken by the patient, help to
treat the infection. The temporary hip allows a person some
movement while healing.
The Wear Problem
The most commonly used FDA-approved joint
prostheses for knees and hips are made of metal and plastic.
The metal is usually titanium or a mixture of cobalt and
chromium. The plastic is a high-density polyethylene.
Although the metal in a prosthesis is highly
polished and the polyethylene is intended to be wear-resistant,
the daily rubbing of these surfaces against each other during
normal movements creates tiny particles of debris. After
many years, these wear particles may damage the surrounding
bone, loosen the prosthesis, and require another knee or
hip joint replacement.
"The 'Achilles tendon' of any artificial joint
over the long term is wear," says Anderson Orthopaedic's
Engh. "Any time you have parts moving against each other,
there has to be wear."
In an effort to solve the wear problem of
metal-on-polyethylene in the hip joint, manufacturers have
produced hip prostheses with three other kinds of surfaces:
metal-on-metal, ceramic-on-polyethylene, and ceramic-on-ceramic.
Unlike the clay ceramic used in pottery, the ceramic used
in hip joint replacements is made from aluminum or zirconium
chemically combined with oxygen for strength and durability.
Metal-on-metal and ceramic hip prostheses
are decades old, but modern materials, designs, and manufacturing
methods have improved upon earlier versions, says Engh.
He cautions that, although modern investigational products
have shown good wear in mechanical simulations in the laboratory,
it's how well they work in people over the long term that
is the real test. "Very often it's best to select an implant
that's been on the market for a while rather than something
that's brand new," says Engh.
A few metal-on-metal and ceramic-on-ceramic
hip prostheses are FDA-approved for use in the general population;
others are approved only for use in carefully controlled
studies. However, a large number of ceramic-on-polyethylene
prostheses are available for use in the general population.
When choosing a prosthesis, the surgeon will
consider many factors, including the patient's age, weight,
gender, anatomy, activity level, medical history and general
health, says A. Seth Greenwald, D.Phil., director of orthopaedic
research and education at the Lutheran Hospital in Cleveland,
part of the Cleveland Clinic Health System. The device's
performance record and the surgeon's own experience with
the device also will be considered.
Choosing the appropriate prosthesis is only
one part of the equation for successful hip or knee joint
replacement. "The most important factor in joint replacement
success is the surgeon," says Greenwald. "The first question
I'd ask the surgeon is, 'How many have you done and what
are your complications?'"
Jonathan Garino, M.D., agrees. "There are
a number of good devices out there," says Garino, an orthopedic
surgeon with the University of Pennsylvania Health System.
"But even if you have the best technology in the world,
it has to be implanted correctly." It falls to the surgeon
to put the device in right, but it falls to the patient
to take care of the new joint, says Garino. Regular exercise
is important, but high-impact activities, such as running
and jumping, generally are discouraged.
The independent panel convened by the NIH
in December 2003 to study total knee replacements also concluded
that proper surgical technique was one of the most important
factors leading to successful knee replacement. Studies
have found that the more knee replacements a surgeon performs,
the lower the rates of complication, according to the panel.
Similarly, complication rates fall in hospitals with increasing
numbers of operations performed.
While prosthesis makers are changing designs,
materials, and manufacturing methods to try to lengthen
the life of artificial knees and hips, surgeons are refining
techniques or developing new ones to try to improve the
outcomes. Doing surgery through smaller incisions and performing
less radical surgeries are among these efforts.
People are seeking minimal-incision knee and
hip replacement surgery, says Engh. Instead of the traditional
6- to 12-inch-long incision used in a standard total knee
replacement, some surgeons are performing the surgery through
a 4- to 5-inch incision. And instead of the typical 10-
to 12-inch incision in a total hip replacement, surgeons
are operating through one 4-inch cut or two 2-inch cuts.
"The [minimal-incision surgery] technique
minimizes trauma to muscles, tissue and tendons and has
less bleeding during surgery," says Garino. Patients have
less pain after surgery, enabling them to walk with full
weight sooner. The hospital stay is usually reduced as well.
"There are many advantages as long as we don't
compromise our ability to put the implants in correctly,"
says Engh, adding that minimal-incision surgery is a more
difficult operation to perform. "If you assemble a model
ship on a desktop, it's easier to do, but if you try to
assemble it within a bottle it is technically more difficult,"
he says. The technical difficulty also adds to the operating
time. "The longer a patient is in surgery, the higher the
risk of infection," says Engh.
Not all patients are candidates for minimal-incision
surgery. People who are obese, have had previous hip or
knee surgery, or those with unusual anatomy may be excluded,
Minimally invasive surgery is another option
for some patients. At Sinai Hospital, Mont performs a minimally
invasive total knee replacement through an incision of 4
to 6 inches, bending the joint through the opening to expose
different parts of it to work on. In a standard knee replacement,
the entire joint is visible through a longer incision. Mont
uses cutting procedures, leg positionings, and techniques
that do not involve dislocating parts of the knee as in
Even as researchers and surgeons continue
to offer more options in prostheses and surgical procedures,
Garino says the current technology is hard to beat. A hip
or knee replacement is likely to last 20 years, he says.
"The average patient takes a million steps a year. I challenge
you to go home and find something in your house that you
use a million times a year that has lasted for 20 years
with no maintenance."
What to Ask the Surgeon
Here are some questions to ask your surgeon
about joint replacement:
- What makes someone a good candidate for joint surgery?
- What are the risks involved in joint surgery?
- Would there be any other non-surgical treatments
I haven't yet tried that would ease my pain and help
me move more easily?
- How would surgery help my particular problem?
- What would not change after the operation?
- How long is the recovery process?
- What is involved in the recovery process?
- What type of procedure would you recommend for me?
- How often in the past year have you performed this
- Can you tell me what the outcome (decreased pain,
improved function) has been for most of these patients?
- Can you provide the names of several people I could
contact to discuss their experiences with surgery?