| Dr. AmstutzWe simply cannot predict how long the hip
resurfacing implants will last for several reasons. First, wear
of implants is a function of how they are used; NOT a function
of time! In other words, durability is directly related to
several factors including the patient’s activity level, quality
of the femoral bone, implant design, the patient’s unique
anatomy and the surgeon’s skill in performing the surgery.
Secondly, it is difficult and inappropriate to prognosticate
about a device’s performance and longevity without long term
clinical data. In the absence of long term data, categorical
statements regarding implant durability are purely speculative.
As the JRI and other centers continue to monitor hip resurfacing
patients post-operatively for longer periods of time (e.g., 5-10
years and beyond), greater quantities of data will have been
compiled and analyzed. Researchers will then be able to present
clinical performance outcomes data to surgeons, patients, health
insurance payors and other interested parties with a greater
degree of statistical confidence. |
| Dr. De SmetWhat is the expected life for the
resurfacing hip as compared to THR?I DON’T KNOW! It is only one of the possibilities to do
longer than 10 years in young and active people! If you don’t
get osteolysis (bone that is going away) or no measurable wear
of the friction couple, metal-on-metal resurfacing can last very
long. Just give me a crystal bal. There are large metal-on-metal
articulations that stayed for more then 30 years. If activity
will play a big part in the wear of the prosthesis, is today
also questionable. |
| Dr. GrossIt depends on your age and activity level.
The best reports on standard metal plastic hip replacement
indicate that in patients with average age 70, 95% last 10-15
years. With these same implants, patients age 40-60, the
implants survivorship drops to 70-80% over 8 years. Metal hip
surface replacement shows 96% survivorship at 7 years in
patients age 40-60. Studies of ceramic-ceramic, metal
crosslinked polyethylene and small bearing total hip
replacements show approximately 95-98% survivorship in young
patients as well. |
| Mr. McMinnHow long will the
implant last?The development of modern hip resurfacings was based on the
secrets of success gleaned from successful historic metal-metal
hip replacements which proved their wear resistance, durability
and biocompatibility over
several decades. The era of modern metal-metal hip resurfacings
started in 1991 when Mr McMinn pioneered them. The early models
were prototypes that gave precious further information on the
best design and material combinations that would make
resurfacing successful. Review of the surviving hips amongst
these early prototype models show that some of them are still
functioning well, in spite of heavy usage over the past 18
years. The hybrid fixed model turned out to be better than the
others. Hybrid fixation was therefore adopted in all later
models. In 1997, the fixation was made even more reliable using
an advanced porous fixation surface and the Birmingham Hip
Resurfacing (BHR) was introduced. Mr McMinn has performed over
3000 BHRs since 1997 and nearly 100,000 BHRs have been performed
worldwide.Orthopaedic surgeons consider that an implant has failed if
following the original surgery, the patient goes on to have
another operation for revision of one or more of the components
of the implant. Failure of the component could be either due to
a fracture, loosening or any other cause leading to pain and
loss of hip function. Nearly 12 years on following the
introduction of the BHR, the failure rate in our group of over
3000 patients is 1.6%. Fracture of the femoral neck or a
collapse of the femoral head due to pre-existing inherent
weakness in the bone or due to premature excess activity early
after the operation led to failure in 1.1%. Infection and some
other very rare causes such as dislocation or metal allergy led
to failure in 0.5%. All of these have then been converted to a
total hip replacement and the patients are back to a normal
lifestyle following their revision surgery.Based on the trend of time to failure of an implant,
statisticians calculate implant survival to denote what
percentage in a given group of patients are likely to reach a
certain time point, such as 10, 15 or 20 years after an
operation, without the need for a revision. In the younger age
group (under 55 years) with osteoarthritis, the implant survival
in Mr McMinn’s series of BHRs is 99.5% at 11 to 12-years
follow-up. The comparative figures for implant survival with the
conventional cemented Total Hip Replacement in this age group
and diagnosis are 81% at 10 years and 33% at 16 years, according
to the Swedish Hip Arthroplasty Register. |
| Dr. SuLongevity of Implant
The short term results (4-6 year follow-up) of hip resurfacing
are encouraging. However, the early failures of hip resurfacing
appear to be greater than for total hip replacement (2.2% vs
1.9%), with the majority of the early failures due to femoral
neck fracture. Whether the newer forms of hip resurfacing will
be successful long term is unknown. It may require 10 years or
longer to determine whether this newer form of hip resurfacing
is as good as total hip replacement at comparable time
intervals. |
| Dr. Jacobs Dr. Michael Jacobs of Good Samaritan Hospital in Baltimore,
Md., says resurfacing devices did not have a smooth beginning
when they were introduced several decades ago.”The devices failed because the sockets were made of plastic,
and the plastic turned out to be the wrong material. It couldn’t
take the stress of the resurfacing device,” says Jacobs.The new devices seem to be working. Eight years of
investigational studies have shown that the metal is holding up,
and the surgeries are successful. But over a lifetime, the
results are unknown. |
|
