Unicompartmental Knee Arthroplasty: A Patient's Guide to Partial Knee Replacement using Minimally-Invasive Surgery (MIS) Techniques.
Edited By: Seth S. Leopold, M.D.
Last updated Wednesday, December 29, 2004
Figure 13 - Model of a traditional total knee replacement. The patella (knee cap) is not shown in this model. Figure 14 - This patient had diffuse arthritis throughout his knee from an old fracture of the tibia (shinbone). It was treated with a traditional total knee replacement. Figure 15 - This patient had rheumatoid arthritis and symptoms throughout her knee, resulting in the traditional total knee replacement pictured here. Figure 16 - Model of a partial knee replacement. This smaller implant leaves undamaged cartilage in other parts of the knee intact. Figure 17 - This patient's arthritis was confined to the medial compartment of her knee. She was a good candidate for minimally-invasive partial knee replacement.
Figure 18 - Minimally-invasive partial knee replacements may be performed for either medial ("inside" of the knee) or lateral ("outside" of the knee) arthritis patterns, provided the symptoms are limited to that one part of the knee. X-rays of two knee replacements are shown here. On the left is a lateral replacement, and on the right is a medial replacement. Considering surgeryWho should consider partial knee replacement surgery for arthritis of the knee and in what cases? It is usually reasonable to try a number of non-operative
interventions before considering knee replacement surgery of any type.
Prior to surgery, your orthopaedic surgeon may offer you medications
(either non-steroidal anti-inflammatory medications
or analgesics like acetaminophen, which is sold under the name
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 the mini knee is a "quality of life" choice.
Patients typically have the procedure when they find themselves
avoiding activities that they used to enjoy because of knee pain. When
basic activities of daily life--like walking, shopping, or reasonable
recreational pastimes--are inhibited or prevented by the knee pain, it
may be reasonable to consider the surgery. What happens if nothing is done for arthritis of the knee (best case/worst case scenarios)? Arthritis is often progressive, and symptoms typically get worse
over time. In some patients, the symptoms wax and wane, causing “good
days and bad days.” Knee arthritis does not usually improve on its own.
What options exist for surgery for arthritis of the knee? If you and your knee surgeon decide that non-operative treatments
have failed to provide significant or lasting relief, there are
sometimes different operations to choose from.
Knee arthroscopy
If your X-rays don’t show very much arthritis, and your surgeon suspects (or has identified by MRI) a torn meniscus, knee arthroscopy
may be for you. This is a relatively minor procedure that is usually
done as an outpatient, and the recovery is fairly quick in most
patients.
However, if your X-rays demonstrate a significant amount of
arthritis, this may not be a good choice. Knee arthroscopy as a
treatment for arthritis fails to relieve pain in about half of the
patients who try it.
Osteotomy
For younger patients (typically under age 40, but this age cutoff is
flexible) who desire to return to a high level of athletic activity or
physical work, a procedure called osteotomy (which means “cutting the
bone”) might be worth considering. This option is suitable only if the
arthritis is limited to one compartment of the knee (for more
information about arthritis in one compartment of the knee, see the "Location" section on page 2 of this article).
Osteotomy involves cutting and repositioning one of the bones around
the knee joint. This is done to re-orient the loads that occur with
normal walking and running so that these loads pass through a
non-arthritic portion of the knee. That’s why it doesn’t work well if
more than one compartment of the knee is involved--in those patients,
there is no “good” place through which the load can be redistributed.
Knee fusion
Knee fusion, also called “arthrodesis,” permanently links the femur
(thigh bone) with the tibia (shin bone), creating one long bone from
the hip to the ankle. It removes all motion from the knee, resulting in
a stiff-legged gait.
Because there are so many operations that preserve motion, this
older procedure is seldom performed as a first-line option for patients
with knee arthritis. It is sometimes used for severe infections of the
knee, certain tumors, and patients who are too young for joint
replacement but are otherwise poor candidates for osteotomy.
Total knee replacement
Long considered the “gold standard” operation for knee arthritis, total knee replacement
is still by far the most commonly-performed joint replacement procedure
(see figures 13). It is most suitable for middle-aged and older people
who have arthritis in more than one compartment of the knee (see
figures 14 and 15), and who do not intend to return to high-impact
athletics or heavy labor. Results of this procedure generally are
excellent, with 90-95% of total knee replacements continuing to
function well more than 10 years after surgery.
Minimally-invasive partial knee replacement ("mini knee")
Patients who are of appropriate age--certainly older than age 40, and older is better--and who have osteoarthritis
limited to one compartment of the knee may be candidates for this
exciting new surgical technique (see figures 16, 17, and 18). Partial
knee replacements have been done for over 20 years, and the “track
record” on the devices used for this operation is excellent. The new
surgical approach, which uses a much smaller incision than traditional
total knee replacement, significantly decreases the amount of
post-operative pain, and shortens the rehabilitation period. The
decision of whether this procedure is appropriate for you can only be
made in consultation with a skillful orthopaedic surgeon who is
experienced in all techniques of knee replacement.
Minimally-invasive knee replacement is not for everyone. Only
certain patterns of knee arthritis are appropriately treated with this
device through the smaller approach.
Generally speaking, patients with inflammatory arthritis (like rheumatoid arthritis or lupus), and patients with diffuse arthritis all throughout the knee should not receive partial knee replacements.
Patients who are considering knee replacements should ask their
surgeon whether the “mini” partial knee replacement is right for them. When performed by an experienced surgeon, how effective is partial knee replacement surgery for arthritis of the knee likely to be and how long will the benefit last? Current evidence suggests that when partial knee replacements are
done well, in properly selected patients, these procedures have about
the same durability as conventional total knee replacements.
Many studies show that more than 90 percent of partial knee
replacements are still functioning well 10 years after the surgery.
Other research indicates that patients who have a partial knee
replacement on one side, and a total knee replacement on the other,
consistently prefer the partial knee replacement. Patients indicate
that partial knee replacements feel more “normal” to them when they
walk and during typical daily activities.
A recent report demonstrated that the minimally-invasive approach
does not interfere with the surgeon’s ability to properly position the
joint replacement components within the knee. This is reassuring in
terms of the likely long-term performance of partial knee replacements
that are inserted using the new technique.
In the event that a partial knee replacement requires re-operation
sometime in the future, it can be revised to a conventional total knee
replacement in a fairly straightforward procedure. Results of that type
of revision are usually very satisfactory. In fact, revisions of
partial knee replacements are typically much easier on both patient and
surgeon than revisions of failed total knee replacements.
There is good evidence that the experience of the surgeon correlates
with outcome in partial knee replacements. It is important that the
surgeon performing the technique be not just an expert knee surgeon,
but comfortable and experienced with the minimally-invasive technique,
as well. How urgent is partial knee replacement surgery for arthritis of the knee? Minimally-invasive partial knee replacement--much like total knee
replacement--is elective surgery. With few exceptions, it does not need
to be done urgently, and can be scheduled around your important
life-events.What are the most frequent and most serious risks of partial knee replacement surgery for arthritis of the knee? How common are they? Like total knee replacement, the mini knee is associated with
certain medical and surgical risks. Although major complications are
uncommon, they may occur; the possibilities include infection, blood
clots, bleeding, and anesthesia-related or medical risks. However, the
overall frequency of major complications following the mini knee is
low, certainly less than 5 percent (one in 20). Later risks include the
possibility that the device may loosen from the bone or that the
arthritis may progress and cause pain in other parts of the knee.
Studies have shown that when the device is correctly placed in
well-selected patients, more than 90 percent of these devices remain in
service and function well more than 10 years after the surgery--a
comparable success rate to total knee arthroplasty. And during that
time, these devices typically function better than total knee
replacements and give patients a more normal “feel” to the knee.
Research indicates that patients who have a partial knee replacement on
one side, and a total knee replacement on the other, consistently
prefer the partial knee replacement.
If risks occur during or after partial knee replacement surgery for arthritis of the knee how are they managed? Most of the major risks of the mini knee can be treated. The best
treatment, though, is prevention. Your orthopaedic surgeon will use
antibiotics before, during and after surgery to minimize the likelihood
of infection. (S)he 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.
Again, the overall likelihood of a severe complication is less than 5 percent when such steps are taken. Surgery for arthritis of the knee 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.
How useful was this page or article?
|
|