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 Nicklaus.
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
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 natural joint.
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 adults.
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
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 the socket.
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 design.
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 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 hip."
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
"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
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 United States.
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
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 other.
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
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
"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, says Garino.
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 traditional
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 operation?
- 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?