What is Hip Replacement? A Review of Total Hip Arthroplasty, Hip Resurfacing, and Minimally-Invasive Hip Surgery.
Edited By: Seth S. Leopold, M.D.
Last updated Friday, January 12, 2007
Considering surgeryWho should consider total hip arthroplasty, hip resurfacing, and minimally-invasive hip surgery? It is usually reasonable to try a number of non-operative
interventions before considering hip replacement surgery for arthritis.
Prior to surgery, an orthopaedic surgeon may offer pills (either
non-steroidal anti-inflammatory medications or analgesics like
acetaminophen, also known as Tylenol), knee injections, or exercises.
Your surgeon may talk to you about activity modification, weight loss,
or use of a cane.
The decision to undergo a hip replacement is a “quality of life”
choice. Patients typically have the procedure when they find themselves
avoiding activities that they used to enjoy because of hip pain. When
basic activities of daily life--like walking, shopping, or reasonable
recreational pastimes--are inhibited or prevented by the hip pain, it
may be reasonable to consider the surgery.
Very rarely, the arthritis can cause a destructive pattern of bone
loss. In this instance, a surgeon might recommend the surgery in order
to prevent a type of pelvic fracture (called protrusio acetabuli), even
if your symptoms are otherwise manageable non-surgically. But again,
this is quite uncommon. In almost all instances, the decision and
timing of hip replacement surgery for arthritis are a personal decision
to be made by the patient, not by the surgeon. The decision should be
made in consultation with a trusted surgeon who can help educate the
patient as to risks, benefits, alternatives, and issues related to
recovery from surgery. If a surgeon says you “need” a hip replacement
for arthritis, without discussing alternatives or asking you about
quality-of-life issues, it might be worth considering getting a second
opinion.
What happens without surgery? Arthritis is often progressive, and symptoms typically worsen over
time. In other patients, the symptoms wax and wane, causing “good days
and bad days.” Hip arthritis does not usually improve on its own.
Sometimes, if the hip becomes quite stiff, this can result in increased
stresses to the lower back with low back pain being the result. As
mentioned, in very rare cases, the arthritis can cause a pattern of
bone loss in the pelvis (protrusio acetabuli) that can predispose
patients to fracture of the hip socket.Surgical options “Traditional” or “minimally-invasive” hip replacement?
This topic, more than any other, is on the minds of patients who come to the office to discuss hip replacements today.
Traditional hip replacement--using an incision that varies
proportionally with the size of the patient, and may be between 5 and 8
inches long--has been done, with a few modifications of surgical
technique, for over 40 years. The results of this approach have been
published by literally thousands of surgeon-scientists, from hundreds
of medical centers, in dozens of countries. There is a known success
rate from this surgery, and it is above 90% with more than 10 years of
follow-up after the operation. It is predictable, and considered one of
the great surgical innovations of the 20th century. It would appear
from this that we ought to set the bar fairly high before trying
something radically new or experimental.
In contrast, “minimally-invasive” hip replacement is a new surgical
approach; few surgeons have even been doing it for two years.
“Minimally-invasive” means different things to different surgeons.
There is no accepted definition--it can be the same operation done
through a slightly smaller incision than the surgeon used to use (say 5
inches rather than 6 or 8 inches), a much shorter incision (an approach
calling for a 3 inch incision is popular in some places), or even two
1.5-inch incisions using an x-ray machine to find the bones and put the
components in the right place.
Surgeons who perform these approaches often say that the shorter
incision results in a number of benefits: shorter recovery time, less
blood loss, less post-operative pain, or fewer days in the hospital.
The problem with these claims is that, to date, they have not been
proved in a single scientific study. And even if one or two studies
come out on the topic, most scientists agree that before advertising
that something in surgery is true, it should be validated by different
surgeons in different medical centers--to make sure that the claims are
in fact true and that the results can be reproduced by others. As of
now, this has not been done.
One might reasonably ask “What could be wrong with a shorter
incision--if anything, the results would be the same, but the scar
would be more attractive, right?” The answer is, not necessarily. If
the shorter incision causes the surgeon difficulty seeing the hip
socket or the thigh bone (femur) clearly, or if it impedes his/her
ability to work in the tighter surgical field, the result could be
badly positioned hip replacement components. That could cause surgical
complications like fractures or nerve injuries, hip dislocations (where
the ball painfully comes out of the socket after the surgery), and
premature wear of the artificial bearing surface.
This is in contrast to minimally-invasive partial knee replacement,
which has been around only a few years longer than the hip technique,
but already has a number of studies proving patients recover faster,
and that surgeons are able to get the components properly positioned
through the smaller incision.
It is particularly telling that the Journal of Arthroplasty, which
is the main research journal for joint replacement surgeons, recently
wrote an editorial criticizing surgeons
who have advertised the “minimally-invasive” hip technique to the
public before any reasonable scientific analysis has been performed on
it.
On the other hand, innovation and new approaches are essential to
the improvement of techniques in all areas of medicine. It seems very
possible that some, if not all, of the benefits of “minimally-invasive”
hip replacement may be realized. It is quite likely that we will learn
much more about this technique in the near future. At this point, it is
reasonable for patients who are attracted to the idea of a more
cosmetic appearance of the shorter incision, and who are not troubled
by the as-yet-unanswered questions about this approach, to consider
“minimally-invasive” hip replacement. Others might consider going with
a traditional surgical approach.
Like so much else in medicine and surgery, this is a personal choice that is best made in view of all the facts.
Links
- Video: Minimally-Invasive Joint Replacement Video
Surgical options: bearing surfaces Polyethylene, metal, or ceramic?
All hip replacements share one thing in common: they include a
ball-and-socket joint. Which materials are used in the ball and in the
socket--which together is called the “bearing,” like a bearing in a
car--has the potential to affect the long-term durability of the joint
replacement.
This is another area where technology may radically change the
outcome of an operation; depending on how the research goes in this
area, hip replacement may look very different in 10 years than it does
today. Or it may not.
Many bearing surfaces have been tried in the 40 or so years that hip
replacements have been done. And many more have failed than succeeded.
That is one reason to proceed with caution, given that we now have a
bearing surface (metal-on-polyethylene) that has a track record going
back to the 1960s.
Polyethylene is a durable, high-performance, plastic resin. It is
slippery (which is why it does well in a mobile joint like the hip) but
it is known to wear out. In fact, while more than 90% of
metal-on-polyethylene bearing hip replacements (this is the most common
bearing in use today) will be in service in 10 years, many of those
will not last 20 years. And when the plastic wears out, it sometimes
results in a destructive reaction causing bone loss around the joint.
This can make repeat hip replacements (called revisions) more difficult.
Many types of plastics have been used in total hips, but only one
(ultra-high-molecular-weight polyethylene) has stood the test of time.
Teflon (like the non-stick material used in frying pans) was tried and
abandoned because of severe reactions by surrounding tissue. Other
modifications of polyethylene have been tried (including
carbon-reinforced plastic), and abandoned because of durability
problems. In fact, there is a new type of polyethylene gaining wide use
today, called highly-cross-linked polyethylene, which shows promising
results in the lab--but little, if any, data are available in people.
Ceramic bearing surfaces are sometimes used. These have been more
popular in Europe than they have been in the United States. They may
result in less aggressive wear, but it is not known whether the wear
they do cause will be more or less of a problem than wear from the
traditional plastic bearings. Also, fractures of ceramic bearings have
been reported; as a result, some of these bearings have been taken out
of service at the direction of the FDA.
Finally, metal-on-metal bearings have become popular. Interestingly,
they were tried early on in the history of hip replacement, but
problems related to their manufacture led to surgeons moving on to
other designs. Now, those problems have been overcome, and they offer
the potential to reduce bearing wear to almost immeasurable amounts.
Some scientists question whether these devices will lead to increased
amounts of metal ions or corrosion products being released in the body,
but to date, these concerns have not been proved to be serious.
However, because the renewed interest in these designs is fairly
recent, there is comparatively little follow-up published in scientific
journals about the longevity of hip replacements using metal-on-metal
bearing surfaces.
The choice of which bearing to use is still somewhat controversial,
and reasonable scientists, surgeons, and patients will sometimes
disagree. This is one of the most exciting areas of research in the
field of hip replacement surgery. But as with surgical approach, it is
worth considering the high likelihood of long-term success using
traditional metal-on-polyethylene bearings when deciding whether to try
another design that does not have results published beyond 10 years.
Surgical options: Hemiresurfacing hip arthroplasty This is a technique that can be used for some patients with avascular necrosis
(also called osteonecrosis) of the femoral head. As mentioned
previously, that is an arthritis-like condition of the hip; it may also
affect the shoulders, knees, or ankles. It is caused by an interruption
of the blood circulation to the ball (the femoral head) of the
ball-and-socket hip joint. This may be caused by trauma to the hip,
excessive alcohol use, use of medical steroids like prednisone, or any
of numerous disorders of blood clotting.
When avascular necrosis is allowed to run its course, the result is
usually severe degenerative joint disease, and the treatment is usually
traditional total hip replacement. Sometimes, when the disease is
caught early, a joint-preserving procedure may be performed, such as
osteotomy (see below), core decompression, or bone grafting.
In an intermediate stage of the disease, avascular necrosis affects
only the ball and not the socket; sometimes the top of the ball
collapses, resulting in a loss of roundness and this causes pain. At
this stage, a resurfacing hip replacement may be an option. This
involves putting a round metal “cap” on the ball, and keeping the
patient’s own socket.
Advantages of this include the fact that it does not take away much
bone (perhaps leaving more options available for subsequent
reoperations), and that it is reasonably durable. Two studies have
found that between 60% and 70% of these devices remain in service 10
years after the surgery. This doesn’t sound great compared to total hip
replacement, which has more than 90% success at that same time period,
but one must remember that patients with this stage of avascular
necrosis are often quite young--anywhere from their 20s to 40 or
so--and so total hip replacement is not considered an ideal approach
for them.
The main disadvantage to this procedure, apart from the failure
rate, is that pain relief is somewhat less than with traditional total
hip replacement--perhaps 80% as good--so many of these patients are
left with some discomfort even after the surgery, although most
patients feel much better with the hemiresurfacing arthroplasty than
they did before.
Patients with avascular necrosis have a complex set of choices to
make, and so it is best for them to find a surgeon who is extremely
comfortable and experienced with a wide array of options to treat the
painful hip. Surgical options: Pelvic osteotomy and hip fusion About osteotomy and hip fusion
Osteotomy is a procedure in which the bone around the socket of the
hip joint is surgically cut so that the socket itself can be
re-oriented. This is best suited for young people with relatively early
stages of arthritis, particularly if the arthritis was caused by a
childhood hip condition called developmental dysplasia of the hip.
Hip fusion is an operation that was more popular in the days before
hip replacements were widely performed. This consists of surgically
attaching the femur (thigh bone) to the pelvis, and causing the two
bones to heal together to become one. It results in loss of motion at
the hip joint, which is obviously a disadvantage, but it is very
reliable at relieving pain. It is seldom done anymore, because most
patients prefer to maintain motion about the hip, but in the right
circumstances, it can still be a good choice. Patients who are
otherwise poor candidates for hip replacement--such as young people who
plan to continue doing heavy manual laborer for a living or young
patients with prior hip joint infections--may decide that hip fusion is
right for them. Effectiveness Current evidence suggests that traditional total hip replacements
last more than 10 years in more than 90% of patients. More than 90% of
patients report having either no pain, or pain that is manageable with
use of occasional over-the-counter medications. The large majority of
hip replacement patients are able to walk unassisted (i.e. without use
of a cane), without any limp, for reasonably long distances. Many have
no distance restrictions at all, and resume hiking, golfing, bicycling,
and other non-impact recreational activities (see figure 9).
As mentioned, there are no studies to date documenting the
short-term or long-term effectiveness of minimally-invasive hip
replacement, and there are no studies that have proved that the joint
replacement components can be reliably inserted with equal success or
safety through the smaller incision used in minimally-invasive hip
replacement techniques.
In the event that a total hip replacement requires re-operation
sometime in the future, the results are generally good--although often
not as good as one typically gets with an uncomplicated first-time hip
replacement. The results of repeat hip replacements (called
“revisions”) often depend on a number of factors that are not in the
surgeon’s (or the patient’s) control, such as: infection, bone loss,
and condition of the muscles and other soft tissues around the hip
joint. But in general, revision hip replacement can achieve a durable
result and provide substantial relief of pain.
There is good evidence that the experience of the surgeon correlates
with outcome in all kinds of joint replacements, including total hip
replacements. It is important that the surgeon performing the technique
be not just a good general orthopaedic surgeon, but an expert,
experienced total hip replacement surgeon, as well. It is reasonable to
ask a surgeon whether (s)he concentrates his/her practice on joint
replacements, or whether (s)he does all kinds of orthopaedic surgery. Urgency Total hip replacement for arthritis is elective surgery. With few
exceptions, it does not need to be done urgently, and can be scheduled
around your other important life events.
Risks Like any major surgical procedure, total hip replacement is
associated with certain medical and surgical risks. Although major
complications are uncommon, they may occur. The possibilities include
infection, blood clots, bleeding or blood transfusion, and
anesthesia-related or medical risks. Certain hip-specific risks, like
infection at the surgical site (typically less than 1.5%), dislocation
(where the ball comes out of joint; less than 1% with one popular
surgical technique), or other problems may also occur. However, the
overall frequency of major complications following total hip
replacement is low, typically less than 5 percent (one in 20) depending
on the individual’s medical risk factors.
Later risks include the possibility that the device may loosen from
the bone; late infections and dislocations may also occur. But again,
numerous studies have shown that a technically well-performed total hip
replacement is more than 90 percent likely to be in service and
functioning well more than 10 years after the surgery.
Managing risk Most of the major risks of total hip replacement can be treated. The
best treatment, though, is prevention. At the UW, orthopaedic surgeons
will use antibiotics before, during and after surgery to minimize the
likelihood of infection. They will take steps to decrease the
likelihood of blood clots, such as early patient mobilization and use
of blood-thinning medications in some patients. Patients are evaluated
by a good internist and/or anesthesiologist in advance of the surgery,
in order to decrease the likelihood of a medical or anesthesia-related
complication. Great care is taken to be certain that the technical
elements of the operation that are so important to success are
correctly performed.
Again, the overall likelihood of a severe complication is generally less than 5 percent when such steps are taken.
Surgery for hip arthritis at the University of Washington If you are interested in making an appointment to discuss this procedure, you can request an appointment using our online referrals website. To request a referral online, please click here. You can also call the Bone & Joint Surgery Center at 206-598-3354 or Eastside Specialty Clinic at 425-646-7777 to make an appointment.
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