The Indications for Total Hip and Knee Replacement
By Dr. William J. Murzic
For most people that eventually undergo total hip or total knee replacement,
an important issue is when to proceed with the surgery. While all patients
must meet certain criteria to be considered candidates for total joint
replacement, the ultimate decision is made by the patient. As pain is
a subjective symptom that varies between patients, only the individual
knows when pain is severe enough to compromise his or her present lifestyle.
Various disease processes can affect hip and knee joint function. By far,
the most common diseases are osteoarthritis and rheumatoid arthritis.
Other forms of arthritis may be caused by previous trauma or infection.
These diseases vary in terms of how rapidly they may progress. The progression
of osteoarthritis is usually a slow process and it may take many years
before substantial symptoms occur. Most candidates for joint implant will
have moderate to severe arthritis which can be seen on plain x- rays.
The medical indications for total Joint arthroplasty of the hip or knee
are 1) significant pain within the affected Joint and 2) functional disability
that is caused by no. 1. All patients should undergo a trial of non operative
(conservative) therapy which includes some or all of the following: pain
medications, nonsteroidal anti-inflammatory medications, weight loss,
modification of physical activities, and use of a cane. Most patients
with mild or moderate arthritis will improve significantly with conservative
therapy. The non-steroidal anti-inflammatory medications, which are a
relatively new class of medicines, are popular as they have anti-inflammatory
as well as pain reducing properties. Most of them can be taken for
extended periods of time as long as certain blood tests are obtained every
three four months. These medications, however, will relieve symptoms but
will not halt the degenerative process.
When conservative treatment fails or ceases to provide adequate relief
and the patient is not a candidate for a less aggressive form of surgery,
then total joint replacement is usually indicated. Ideal candidates are
over the age of 60 as they are less active and will place less demand
on the implant when compared to someone younger. Total knee and total
hip arthroplasty can provide excellent pain relief and functional improvement.
Every patient who undergoes surgery should realize that the reconstruction
creates a good joint but not a normal joint. The prosthetic joint should
provide significant pain relief and improved, but not normal range of
motion. The arthroplasty will enable one to perform normal activities
of daily living as well as activities such as swimming, bicycling, and
golf.
The indications, therefore, for total knee or total hip replacement are
severe joint pain and disability that do not improve with nonoperative
treatment. When performed under the appropriate conditions, total joint
replacement of the hip or knee will allow a more independent and higher
quality lifestyle.
Update on Dental Pre-medication
The American Heart Association has
recently revised its recommendation on premeditation for dental and other
invasive procedures for patients with prosthetic implants. Amoxicillin has
been chosen over penicillin due to better absorption and higher more sustained
serum levels. For patients with no known allergy to penicillin, dosages
are:
Amoxicillin 3.0 gm one hour prior to the procedure, then Amoxicillin
1.5 gm six hours following the procedure.
Recommendations for those patients with a known allergy to
penicillin remain the same.
Return to top Patient Concerns
Please explain the meanings of some of the of the terms used when I hear
or read about total Joint replacements.
Here are a few words used in this office in relation to hip and knee problems:
Allograft: Tissue (in our case, bone) from one individual
transplanted to another individual. Arthroplasty: Surgical procedure to remodel a joint
as in a total hip or knee replacement. Arthrodesis: The fusion of bones across a joint by (usually)
surgical means, which eliminates movement. Occasionally an arthrodesis of
a joint can be the result of disease or trauma. Osteotomy: Surgical cutting of a bone to change the
alignment or alter the weight-bearing stresses. Custom Prosthesis: A hip or knee joint designed to be
used on an individual patient. NSAID: An acronym to describe non- steroid al anti-inflammatory
drugs, including aspirin and ibuprofen. There are several of these types
of drugs available over the counter, others require a physicians prescription. Autologous: The use of your own bone or blood during
a surgical procedure. Homologous: The use of blood or bone obtained from a
donor bank. Aspiration: Removal of fluid from a hip or knee Joint.
This fluid is then sent to a laboratory for diagnostic studies. Hybrid Prosthesis: A prosthesis where one component
is cemented and the other is cementless.
Return to top Staff Profile: Inez Willett, R.N.
Born in Manchester, England, 1929; Inez Willett came to the United States
in 1948, settled in Sacramento and married. Inez started her nursing career
in England and resumed her profession after the birth of her first daughter,
Suzanne, in 1957. Until her second daughter, Lisa, was born in 1958, she
continued to work part-time plus was active with the Blue Birds Campfire
girls as well as the PTA. Inez returned to full-time nursing in June of
1966 at what was then the Sacramento County Hospital, which is now UC Davis
Medical Center.
Her reason for choosing orthopaedic nursing was prompted by a resident who
took a few minutes out of his busy schedule to explain the principles of
skeletal traction as it applied to a severely injured restless patient.
She later transferred from the intensive care unit to the orthopaedic floor,
taking every opportunity to enhance her knowledge of orthopaedic nursing
by attending seminars all over the United States. As a visiting nurse Inez
observed a large orthopaedic hospital in Oswestry on the English-Welch border.
It was in 1981 when Dr. Bargar joined the orthopaedic faculty as an assistant
professor that Inez made his acquaintance. Inez worked very closely with
Dr. Bargar at the clinic and it happened that her retirement as head nurse
in June of 1986, coincided with his plans to go into private practice. At
this point she was back to part-time nursing again until illness forced
her to resign in 1989. Since then, Inez has moved to Oregon to be close
to her only grandchild, and has once again starting working two days a week
in Medford. In addition to this part-time Job, she is the editor of the
Joint Effort publication.
Update on Research Projects
Many of you have expressed interest in the research projects that we currently
have underway. These are both clinical and basic science type protects.
The clinical (patient related) projects are conducted in the office by
Drs.' Bargar and Taylor with the Fellow. The basic science laboratory
projects are conducted at the Sutter Institute for Medical Research (SIMR)
or at the Orthopaedic Research laboratories at U C Davis. Many engineers,
scientists, graduate and undergraduate students work on these projects
with us. What follows is a brief summary of current projects:
1. Custom Cementless Femoral components in Primary and Revision Total
Hip Replacement-This is an ongoing clinical study which began in 1985,
when the idea of using CT based CAD/CAM (Computer Assisted Design/Computer
Assisted Manufacturing) custom implants was developed by Dr. Bargar. Each
implant is custom designed for each patient to obtain optimum fit of the
prosthesis. Nearly 300 cases have been performed and are followed regularly
with prospective rating forms and x-rays. Current results show approximately
95% success rate for primary (first time) hips and 90% for revision hips.
These results appear to be better than other "off the-shelf"
implants, but it is not yet proven statistically.
2. Custom Oblong Acetabular Components as a Method of Managing Bone Loss
in Revision Total Hip Replacement-This is another clinical study in which
bone loss in the socket of the hip Joint is managed by making CT generated
foam models and designing custom implants to fit the defects. This is
felt to be superior in certain cases to the alternative of allografting
(use of another person's bone). Patients and x-rays are followed at regular
intervals and results have been reported at several national meetings.
3. Development of a Classification System for Bone Defects in Total Knee Replacement-This
is being developed to aid others in describing and reporting bone defects
in the knee that require special treatment at the time of total knee replacement.
Patient records and films are being retrospectively reviewed to develop
and refine this classification system. It is planned to submit this to
the next meeting of the Knee Society.
4. Long Term Fate of Hydroxylapatite (HA) Coating in Total Hip Replacement-
Hydroxylapatite is currently the coating of choice of Drs.' Bargar and
Taylor for fixation of cementless hip replacements. Much is known about
the short term efficacy of this material, but longer term information
is sparse. This is a canine study in which two groups of dogs will be
compared at one year follow-up: one group with HA coated implants and
the other with conventional porous pads.
5. Optimization of Substrate Preparation for HA Coating. This is a joint
study, soon to be underway, sponsored in part by Bio- Interfaces,
Inc. of San Diego. This is the company currently coating the custom implants
with HA. This study will investigate the optimum surface preparation for
adherence of hydroxylapatite coatings.
6. Stress, Strain and Micromotion Evaluation of Femoral Components - This
has been a three year project undertaken by Dr. Dan Hayes at UC Davis
to determine the best way to measure stability and stress transfer of
cementless femoral components. This technique has been used to compare
custom prostheses to various off-the-shelf devices and will serve as the
standard method of evaluation of all femoral component designs in the
future. Dr. Hayes recently received his Ph.D. for this work-Congratulations,
Dan.
7. Analysis of Acetabular Component Bio-Mechanics- This is a current basic
science research protect designed to determine the effect of design and
insertion technique on the fit and stability of acetabular cementless
components.
8. Robodoc-This very large project has been described in previous issues
of Joint Effort. Integrated Surgical Systems, Inc., a newly formed company,
is integrating the software and robotic hardware to allow production of
this surgical robot. Research continues on the development and application
of this system. The first human use awaits FDA authorization, but hopefully
will take place in late 1991 or early 1992.
9. Evaluation of Partial vs. Full Cementing of Tibial Components in Total
Knee Replacement-This is a project we hope to get started this summer
with funding from Johnson & Johnson. This laboratory study will compare
two current techniques for cementing tibial components and determine which
is best.
10. Development of a Computer Workstation for the Design of Hip Implants-As
a spinoff of the imaging work done for the Robodoc project, it is felt
we have the basic elements required to allow development of a computer
workstation that will allow engineers to better design implants based
on 3-dimensional analysis of CI scans.
More, smaller projects are underway, but space does not allow mention
of all. Funding is needed for all of these projects. Interested donors
should send tax deductible checks to the Office made out to either to
Regents, University of California for projects at UC Davis) or Sutter
Institute for Medical Research. Any support would be greatly appreciated.
Hip
& Knee indications