Barry J.
Waldman, MD and Esther A. Schaftel, CRNP
An Arthritis Epidemic Unfortunately,
there is an epidemic of knee arthritis in the United
States. The American Academy of Orthopaedic Surgeons,
estimates that between 2006 and 2030, the number of knee
implants performed in the United States will increase from
300,000 a year to nearly 3.5 million. Even more concerning,
the average age of knee implant patients gets younger each
year1. It is not unusual for patients as young as 40 to
experience severe knee arthritis and require knee implant
surgery. Women account for about 60% of patients who need a
knee implant - a proportion that has remained steady for
the past few decades.3
Because the market for knee implants is growing so rapidly,
there is intense competition between manufactures of
implants for future business. Orthopaedic implant
manufactures are working hard to convince surgeons and
consumers that their knee products are superior to
their competitor’s products. Because knee implants
are very similar to one another, manufacturers have begun
to market directly to consumers to increase their brand
recognition and steer patients to their implants.
Implant Manufacturers The four major
manufactures are Zimmer, Stryker, DePuy (a division of
Johnson and Johnson) and Biomet. All have very similar
implants that work extremely well if they are implanted
correctly. This has forced many of them to
differentiate themselves using some unproved claims.
Recently, Zimmer has been marketing a “gender-specific
knee”, targeted at women. It claims that it has designed "a
total knee system with the women in mind".3 In
response, Stryker has asserted that their "design closely
matches the anatomy of a female knee.3 and Biomet Inc.
states the differences between sexes are not enough to
warrant a difference in designs.3
DePuy has advocated a rotating platform knee that “bends
and rotates.” to better match natural anatomy. While, these
designs may have some benefit, there is no long-term data
proving that they are any better than any other modern
design. Differences in patient anatomy have long been
recognized and incorporated into knee designs. These
differences have far more to do with the patients overall
size, not their gender or race.
Additionally, these newer implants may have some
detrimental effect that isn’t obvious today, but will
become apparent some time in the future. Because knee
replacements are so durable and work so well for most
people, it will take many decades to sort out the effect of
new designs. To further confuse patients, hospital and
doctors have begun to advertise directly through local
media and the internet. Many claims made are not reviewed
by other doctors and may be somewhat exaggerated. Surgeon
and hospital advertising often focuses on “minimally
invasive” procedures. While a smaller incision can be
beneficial, there is no agreement amongst surgeons as to
the best methods to use. Some of these techniques have a
higher complication rate and may cause more problems then
they help.4
Advice to Patients
With the barrage of questionable information contained in
advertising and on the internet, what can a patient do to
obtain the best possible knee? Multiple studies have shown
that the overall success in knee replacement can be traced
to the surgeon and the team that cares for the patient
during and after surgery. Surgeons and centers that do
large numbers of implants have more success, on the
average, than surgeons who do this type of surgery less
often. When considering a doctor, it’s important to ask how
many operations of this type they do each year and what
their personal outcomes are. The hospital they use should
have a dedicated joint center and do a large number of
joint replacements each year. It is also important to find
a physician that responds in a timely manner to phone calls
and patient requests.
Almost all of the knee implants available today are the
result of years of research and should offer excellent
functional performance and longevity.1 Patients
should be able to reap the benefits of any TKA with the
right surgeon with the right supportive team. Try to view
all the advertising and hype with skepticism and you won’t
be fooled by unsubstantiated claims. It is far more
important for patients to find a doctor that they feel
comfortable with and that they can discuss their concerns
with, rather than worry about the implant used.
References 1. Dennis DA.
Trends in total knee arthroplasty.Orthopedics. 2006 Sept;29
(9 Suppl): S13-6. 2. Barrett WP. The need for
gender-specific prosthesis in TKA: does size make a
difference? Orthopedics. 2006 Sept; 29 (9 Suppl): S53-5. 3.
Ptacek G. Gender-specific knee implants. Orthopedic
Technology Review. 2006 May-June. 4. Booth RE. The
gender-specific (female) knee. Orthopedics. 2006 Sept;29 (9
Suppl): S768.5. Waldman BJ,
Jackson G, Schaftel EA. Complications of Quad Sparing Total
Knee Arthroplasty, Annual Meeting, American Academy of
Orthopaedic Surgeons, Feb. 2007, San Diego CA