Download Mark E Endicott M.D. 2801 K. St Suite 500 Sacramento, CA 95816

Mark E Endicott M.D.
2801 K. St Suite 500
Sacramento, CA 95816
(Phone) 916-733-8710
TOTAL KNEE REPLACEMENT: BENEFITS, RISKS, AND
ALTERNATIVES
by: Mark Endicott, MD
INTRODUCTION
If you are contemplating having a total knee replacement, I feel you
should know the facts as much as they are known about the expected
benefits, as well as, the risks and possible complications of the
procedure. This information booklet is designed to review these facts
with you, so may make a more intelligent decision regarding surgery.
NON-OPERATIVE TREATMENT
In my opinion, total knee replacement is not a conservative
operation. In the procedure your bone and joint is removed and it is
replaced with plastic and metal components. You become dependent
on the function of these components and any failure of the
components can result in pain and loss of function. I feel you should
exhaust all reasonable non-operative measures to control pain and
maintain function prior to considering total knee replacement.
Arthritis of the knee is by definition a wearing away of cartilage. The
cartilage that lines the knee is an exceptional material. It is smoother
than any man made bearing. The cartilage has no nerve endings in it
and therefore, any motion between cartiliganious surfaces does not
cause pain. As the cartilage wears away, however, debris is
generated which causes an inflammatory response
which produces pain and also accelerates the destruction of the
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joints. The underlying bone does have nerve endings in it and also is
not a good bearing material, any motion between bones without
cartilaginous surfaces causes significant pain.
The mainstay of non-operative treatment is to control this process by
decreasing the force applied across the joint, as well as decreasing
the number of times that the force is applied. In addition, antiinflammatory medications will help control the symptoms. In order to
decrease the force, several things can be done. The first is weight
loss; any excess weight causes significant extra force across the joint
which increases the joint destruction as well as pain. Because of the
muscles acting across the knee joint, normal walking causes force
across the knee approximately three to five times of the body weight.
Therefore, if you are 20 pounds over weight, the force across the
knee is increased by almost 100 pounds. Any effort at weight loss will
decrease the force about the knee, slow down the destruction of the
knee joint and decrease pain. Another way to decrease force is to use
a cane or crutch. Usually, it is used in the opposite hand, but can be
used in the hand of the same side as the involved knee. Avoidance of
unnecessary activities such as jumping, jogging, impact loading or
heavy lifting ( greater than 20 pounds) .
In the 40-60 age group, patients with bowed legs or knock-knee
deformity, an " osteotomy" of the knee may be the best operative
procedure. This is where the upper end of the tibia bone near the
knee is cut and a wedge of bone removed to straighten the leg. This
procedure requires that some portion of the knee still have viable
cartilage on it and is not possible when the cartilage is completely
destroyed. This procedure has approximately a 70% success rate
and success is defined here as improvement of symptoms rather than
complete freedom of pain. It is however a conservative operation that
preserves the knee joint and can allow future conversion to a total
knee replacement.
Another alternative is " arthroscopic debridment". This is when an
arthroscope is inserted into the knee and various instruments are
used to remove arthritic debris from the joint. Areas of full thickness
loss of cartilage may be drilled or abraded. This procedure usually
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gives temporary relief of approximately six months but occasionally
can work for several years. If there is x-ray evidence of
SEVERE arthritis, arthroscopic debridement is usually not advised.
A final alternative is " partial knee replacement" ( uni-compartmental
knee replacement). This may be applicable if only one compartment (
medial or lateral) is worn away and the remainder of the joint still has
good cartilage. This is usually NOT recommended under age 50,
when an osteotomy might be tried.
In your particular case one of these alternatives may be applicable.
This should be discussed with Dr. Endicott.
BENEFITS OF THE PROCEDURE
Total knee replacement is one of the most successful of all surgical
orthopedic procedures. Total knee replacement initially got a bad
name as compared to total hip replacement. Early designs did not
take into account the complicated biomechanics of the knee joint. In
the mid -1970's, an engineer by the name of Peter Walker designed a
" semi-constrained" knee replacement called the
" Total Condylar" knee. This design allowed stresses to be taken up
by the ligaments and yet had enough constraint to provide stability.
Use of these prostheses and various modifications such as
preserving the posterior cruciate ligament and development of more
accurate instrumentation has allowed the success rate to increase
dramatically. At the present time, knee replacements are felt to
succeed 95-98% of the time; these results are actually better than
total hip replacement.
A "success" is defined as freedom of pain and restoration of motion
as well as function. A successful knee replacement will allow a person
to return to the routine activities of daily living. Certain restrictions do
apply however. Persons with total knee replacement should not
expect to resume to jumping or jogging activities or any impact
loading. Lifting of weights of greater than 50 pounds should be
avoided. Singles tennis and racquetball are not advised but golf,
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swimming, and bicycling are good exercises. There are also some
restrictions of motion. Although the leg with a knee replacement can
flex up to 120 degrees, it is not advised that you attempt to bend it
more.
An ideal candidate for total knee replacement is a patient who is over
65, relatively sedentary, with normal mental capacity, and who is not
overweight.
The converse of this represents the so called " high risk patient" for
total knee replacement; namely those who are under 65, overweight,
excessively active or who have had a previously cemented total knee
that has failed. The relative success rates and risks in this group are
discussed below.
In summary, if you are an ideal candidate, the expected benefits from
total knee replacement should be 95-98% chance of relieving all of
your pain and restoring motion and function for routine activities of
daily living.
RISKS AND POSSIBLE COMPLICATIONS
The two major complications that can cause failure of a total knee
replacement are infection and loosening. Infections has a very small
chance of occurring ( 1 out 100 in first time knee replacements, and 4
out of 100 for revision knee replacement), but if infection occurs, it is
a very difficult problem to treat. Most infections in total knee
replacement occur due to contamination at the time of surgery or
subsequent wound breakdown. It is a myth that surgery can be a truly
sterile procedure. Any time that people are in an operating room,
there will be a small number of bacteria that can settle in the wound.
We take many precautions to decrease the number to a minimum.
These include the use of sterile instruments and drapes as well as
gowns and masks and head covers. In addition to these routine
procedures, the surgery is preformed in an " ultra clean room" or
"laminar air flow room". In this type of operating room, a uniform flow
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of filtered air is continually circulated over the wound. Another
measure to decrease infection is the use of " prophylactic antibiotics".
This means to use antibiotics in advance of surgery to prevent
infection rather than treat it after it occurs. Prophylactic antibiotics are
usually given within an hour of surgery and sometimes we use
antibiotics during surgery and for 48-hours after surgery.
If an infection occurs in a total knee, every effort is made to retain the
prosthesis but less than 50% of the time is this successful. If the
implant is loose or if the infection continues to recur, it is usually
necessary to remove the implant completely in to order to cure the
infection. This of course, leaves no knee joint and although walking is
possible usually two crutches are required, the leg requires a brace
and motion is minimal. At least six weeks of intravaneous antibiotics
are required to treat the infection. After three weeks, consideration
can be given to reimplantation of a total knee but statistics show that
20% of reimplantation cases develop infection again. Therefore, not
frequently is the knee fused in a second procedure. The second
major complication is that of loosening. The key success for a total
knee replacement is that all motion should occur between inert
materials( i.e. metal and plastic). If any movement occurs between
the implants and their respective bones (i.e. loosening), this will
cause pain, bone resorption and ultimate failure. Loosening usually
takes several years to develop and can occur as late as 10 to 15
years for a cemented implant. The process of loosening is attributed
to failure ( cracking) of the cement used to anchor the implant to the
bone. It is felt that this cracking is a " fatigue failure" caused by
multiple repetitive loads or loads that are excessively high in certain
areas. This can also be caused by poor alignment of the implant.
The risk of loosening in ideal candidates is approximately 1% - 3% in
10 to 15 years. In non-ideal candidates such as patients with
excessive body weight and younger, more active patients as well as
patients who have had a previously failed cemented implant, the
chance of loosening increases.
Revision total knee replacements require special mention. A revision
is defined as a total knee replacement done for a previously failed
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implant. The chances of success in revision knees is only 80%
compared to 95% to 98% for primary procedures and this is for a very
short term. Most of the causes for failure have been loosening.
Infection is also increased up to approximately 4%.
Other possible complications need to be mentioned. Instability can
occur due to poor ligament balance. This can cause buckling when
weight bearing and may require the use of a knee brace and/or cane.
Usually it is not painful. Rarely is revision surgery needed to correct
this problem. Instability is relatively rare with only 1-2% having a
functional problem.
Another complication that should be discussed is blood clots that can
form in the legs or pelvis. In and of themselves, the blood clots are
not a threat; they can be treated with blood thinners and will
ultimately resolve. The big concern, however, is that a portion of the
blood clot can break off and go to the lung " pulmonary embolus". If
that occurs, it can be life threatening. Various preventative measures
are used to decrease the risk of blood clots forming. You are normally
given a blood thinner, which is usually coumadin, during your hospital
stay and most times will continue even after you have been
discharged home. This blood thinner helps prevent clot formation.
Compression stockings and Continuous Passive Motion (CPM)
machines are also used but early ambulation beginning on the first
day after surgery and active bed exercises such as ankle "pumps"
are most hopeful.
There is additional information available on the internet if further
research and information is desired to assist you in your decision. My
office staff is also available to answer any further questions that you
may have.
The following is a link from the American Academy of Orthopaedic
Surgeons:
http://orthoinfo.aaos.org/topic.cfm?topic=A00389