Hip resurfacing has evolved over the past decades with advances in
design, metallurgy and surgical techniques. Sir John Charnley
carried out the first Hip Resurfacing in the 1950's. Teflon
components were used, which unfortunately wore out within two years
of implantation. This failure of materials plagued the orthopedic
community for several decades. The 1970's was the next significant
development of hip resurfacing, with the usage of metal femoral
heads, with polyethylene acetabular cups which were fixed with
cement. About 55% of these resurfacings failed within 6 years after
implantation due to excessive wear of polyethylene.
In 1990, Derek McMinn and Ronan Treacy of the Royal Orthopedic
Hospital at Birmingham pioneered the metal-on-metal resurfacing
prosthesis called the Birminhgam Hip Resurfacing (BHR) Prosthesis
composed of Cobalt Chrome at both Femoral and Acetabular sides.
Unlike conventional Total Hip Replacement (THR), hip resurfacing is
conservative in that the femoral head and neck of the hip joint are
not removed nor is bone removed from the femur. In the case of
surface replacement, less bone is also removed from the acetabulum
as compared to conventional THR since no polyethylene liner is used.
X-ray (left), showing post-BHR procedure where the femoral head is
reshaped to accept metal cap with small guide stem. Head size is
about 50 mm in diameter. Metal cup is set into pelvis. As a result,
the femoral bone is loaded more like a normal hip and the bone is
preserved. Since the resurfaced head is very similar in size to the
normal hip (about 40-50 mm), it is more stable and dislocation risk
is minimal. An example of a surface replacement is shown in Figures
6a and 6b.
Several different hip resurfacing
systems were introduced in five countries in the early 1970s. They
were implanted in young patients who were expected to require more
than one replacement in their lifetime because they were thought to
be more conservative devices than the conventional replacements.
Some surface replacements with polyethylene have had long-term
durability of up to 18 years thus far. However, because of the large
diameter ball size of the surface replacement, there was more
polyethylene bearing wear (the debris accumulation which undermines
the fixation) which results in loosening of the prosthesis. Most
surgeons abandoned surface replacements with polyethylene in the
1980s and early 1990s. Despite the fact that the durability was
often less than desired, the femoral bone preserved by these systems
was especially valuable for these young patients when revision
surgery was required making that second surgery comparable to
The conservative and more physiologically compatible nature of the
surface replacement has always been appealing to both surgeons and
patients. There is renewed interest which has been fostered by the
reintroduction of all-metal bearings which could dramatically
increase the durability. The first of these metal/metal surface
replacements was introduced in Germany and subsequently in England
and at the Joint Replacement Institute (USA) in the early 1990s. The
instruments and design have been improved using modern techniques to
further reduce wear and to facilitate the procedure. The major
advantage of the surface replacement is in the preservation of the
femoral head and neck. Further, unlike the acetabular reconstruction
with the earlier designs which contained polyethylene bearings, very
little bone is removed and the procedure is now conservative on the
acetabular pelvic side of the joint as well. In short, no "bridges
are burned" with the surface replacement procedure.
Surface replacement may also permit higher levels of post- surgery
activity with fewer downside risks than does a stem-type device. The
increased stability is particularly conducive for sports and work
activities where a more normal range of motion of the hip is
The lessons that we have learned regarding design and technique
issues during the past 25 years combined with the modern precision
manufacturing of metal/metal bearing surfaces have led to a very
much improved device. Although it is impossible to predict how much
increased durability will be achieved, the volumetric wear reduction
is substantial, and it is unlikely that these devices will "wear
out". We also believe that the metallic wear debris, based on
our histological observations to date, appears to be well tolerated
in the tissues. Potential long term undesirable consequences of
these devices are unknown. However, they have been successfully
implanted for over thirty years so we believe the risk is minimal.
Following total hip replacement, joint surfaces will again be
smooth and slide easily. This gives most patients pain relief, an
increased range of motion, and unlimited walking ability. You may be
able to take part in physical activities which before surgery were
impossible. However, your hip will not be normal - remember that you
will have a prosthetic joint!
An incision is made into the buttock and access is gained to the
hip joint. The prosthesis chosen is the one closest possible to the
normal size of the hip (small people have small joints and large
people have large joints, as you would expect). Great care is taken
to keep the wound as small and as neat as possible.
The reason such careful attention is paid to the size of the
replacement part is because it means there will be less chance of
dislocation, the risk being very minimal anyway (less than 1%),
which decreases over time and by six weeks post-surgery this risk is
really quite insignificant.
The difference between a total hip replacement and a resurfacing
procedure is that a total hip replacement is a much more invasive
operation in that the top of your femur, or thighbone, the size of a
golf ball, has to be removed so that the prosthesis, or false joint,
may be fitted. When a resurfacing is performed, the arthritic bone
is simply shaved away and the new ball and socket, or prosthesis, is
fitted over your existing bone and cemented into place.
Cobalt-chrome cast parts. Parts are precision machined to fit each
other with small space for body fluid to lubricate. The backside of
the cup has a roughened surface to allow bone to grow into implant.
Advantages of The
Birmingham Hip Resurfacing
Special Risks of
- Femoral head is preserved.
- Femoral canal is preserved and no associated femoral bone
loss with future revision. Also, the risk of microfracture of
femur with uncemented stem implantation is eliminated.
- Larger size of implant "ball" reduces the risk of
- Stress is transferred in a natural way along the femoral
canal and through the head and neck of the femur. With the
standard THR, some patients experience thigh pain as the bone
has to respond and reform to less natural stress loading.
- Use of metal rather than plastic reduces osteolysis and
associated early loosening risk.
- Use of metal has low wear rate with expected long implant
Requirements of Resurfacing Patients
- Lack of long-term track record. Current device has only been
used for about 7 years. Despite known low wear rate, longevity
and longterm effects of wear debris are unknown.
- For some surgeons, the procedure has a longer surgical time.
The procedure requires somewhat more skill of surgeon.
Risks and Potential
- Solid bone in femoral head to hold resurfacing component. A
few cysts or slight AVN collapse may be acceptable.
- Healthy kidneys to process any blood borne metal ions from
All surgeries have risks, so the potential benefits must be
carefully weighed. Some complications are related to the surgical
procedure and some are related to the delicate balance of the body
which is altered during the operation.
Potential complications of any surgery include: the risks of
anaesthesia, bleeding, infection, blood clots, and death. With
modern techniques, the risk of anaesthesia related complications is
very low. Epidural anaesthesia (which numbs your legs) has the
advantage of enhanced post operative pain relief and potentially
less blood loss. If a blood transfusion is required, there is a
potential risk for a transfusion reaction or disease transmission
(e.g. hepatitis), and therefore, autologous blood (your own) is
preferred. Prophylactic antibiotics, strict sterile technique, and a
special airflow system are used to help prevent infections which
occur in less than 1% of cases.
Leg elevation, elastic stockings (TED stockings), ankle exercises,
and Coumadin (blood thinning medicine) are used to help prevent
blood clots. Tables 1 and 2 below list factors which can increase or
decrease the risk of thromboembolic disease (blood clots). A
thorough medical evaluation is required prior to surgery which can
help identify other potential medical problems and, thereby,
minimise those risks.