TOTAL HIP REPLACEMENT (THR)
Hip Joint replacement or Total Hip Replacement is surgery to
replace all or part of the hip
joint with an artificial device to restore joint movement
There are different types of hip replacements. If a
hemi-arthroplasty is performed, either
the femoral head or the hip socket (acetabulum) will be replaced with
a prosthetic device.
In a total hip replacement, both the femoral head and the hip socket
is replaced by the
WHAT IS ARTHRITIS AND WHY DO JOINTS WEAR
The normal joint in our body is made up of two bones which are
lined by surface
cartilage. The joint is surrounded by a capsule which has a thin
lining of synovial cells
which produce a thin layer of lubrication film. The lubrication film
together with the surface cartilage (articular cartilage) acts as a
and allows the joint to move smoothly and lasts for many, many years.
If the surface cartilage is badly damaged or if the joint surfaces
are not aligned properly
(example, in a shallow hip) then the cartilage will wear out much more
quickly than the
normal wear and tear and as a result the bone under the cartilage
layer is exposed. The
exposed bone starts to rub against each other and the process of
and tear) is established.
Osteoarthritis is therefore the result of mechanical wear and tear
on a joint. The main
feature is a loss of surface cartilage with bone rubbing on bone. This
pain. The body tries to relieve this pain by increasing the amount of
fluid in the joint.
This is why joints are sometimes swollen. The formation of bone spurs
and cysts around
the joint is another hallmark of osteoarthritis.
In an arthritic hip
- The cartilage lining is thinner than normal or completely
absent. The degree of
cartilage damage and inflammation varies with the type and stage of
- The capsule of the arthritic hip is swollen
- The joint space is narrowed and irregular in outline; this can
be seen in an
- Bone spurs or excessive bone can also build up around the edges
of the joint.
The combinations of these factors make the arthritic hip stiff and
limit activities due to
pain or fatigue.
- The diagnosis of osteoarthritis is made on history, physical
examination & X-rays
- There is no blood test to diagnose Osteoarthritis (wear & tear
You are admitted to the hospital and after appropriate
pre-operative tests and admission
procedures you will be taken to the operating theatre. The
anaesthetist will discuss with
you the type of anaesthetic. Anaesthesia may be either general or
regional. With a general anaesthetic you are asleep and with a
regional (spinal or epidural) your legs and hips are
numb allowing you to have the operation without pain. Usually the
anaesthetist will either
sedate you or give you a full anaesthetic if you have a
Most approaches to the hip are done with the patients lying on
their side. When you are
asleep you are positioned in a special brace that stabilises your
pelvis and keeps you on
your side. An incision is made along the side of your hip joint and
the muscles carefully
split and divided to expose the hip joint.
The worn out joint is exposed and the femoral head is resected.
This allows visualisation
of the acetabulum (socket). The socket is then cleared of debris and a
reamer is inserted to appropriately fashion the socket to accept the
artificial acetabular component.
After reaming is complete, the artificial socket is inserted. There
are two types of sockets,
(a) a cemented socket or (b) an uncemented socket. A cemented socket
is cemented into
the bone and an uncemented socket allows bone to grow into it. Your
surgeon will advise
you which is the most appropriate socket for your bone quality.
An uncemented socket has the ability to accept a socket lining
which is either polyethylene
(special plastic), ceramic or metal. The liner is inserted into the
socket. Ceramic and metal articulating joint surfaces have lower wear
rates than plastic sockets and therefore tend to
be used in younger patients. The newer plastics last a lot longer than
the older ones and are appropriately used in older patients.
After preparation of the socket, the femoral bone is prepared with
various instruments to
accept either a cemented or an uncemented femoral component. Once the
canal is prepared
the femoral stem is inserted with or without cement. A trial femoral
head is placed on the
stem and the hip is reduced. During the trial reduction the hip is
and put through a range of motion. At the same time leg lengths and
stability are examined.
Following the trial reduction the appropriate head is then placed
on the stem and the hip is
reduced. Occasionally leg lengths may not be entirely equal in order
to tension the hip
appropriately and thereby prevent dislocation.
Following insertion of the components the wound is closed usually
with absorbable sutures
and a drain is inserted.
What about the bearing (articulating) surface?
When the first hip replacements were made 35 years ago, it was
found that over time
they started to wear out and loosen. The reason they wore out was that
(polyethylene) particles were released from the socket which caused a
small inflammatory response. This inflammatory response around the
prosthesis caused the bone to weaken
and the prosthesis to loosen and therefore a revision was needed.
inflammatory areas can become large cysts and structurally weaken the
bone so that
when the hips are revised extra bone is required to fill up these
defects. This extra bone
may be taken from the patient or may be allograft bone, which is bone
that has come
from a bone bank.
In order to reduce the amount of wear particles, newer technologies
have evolved. This
includes new polyethylene, ceramic on ceramic and metal on metal
articulations. The wear
rates of ceramic on ceramic and metal on metal are 10 to 100 times
less than the original
Newer technology surfaces are tested in a laboratory on hip and
knee simulators. The
tests are extremely encouraging but only time will tell if they prove
to be as successful as laboratory tests show. Younger patients tend to
have ceramic or metal articulations in the expectation that less wear
will occur and the joint will last longer.
When comfortable the physiotherapist will get you up and start your
will be shown exercises to strengthen the muscles of the hip joint and
you will also be
shown the positions that you may keep your leg in and positions that
will avoid hip
dislocation. Initially you may start with a walking frame but then you
will progress to
crutches and a walking stick. Depending on your surgeon's preferences
you will either
fully or partially bear weight. The wound will have a waterproof
dressing over it, which
will allow you to shower. It is important to mobilise as soon as you
are comfortable as this
will prevent complications such as deep vein thrombosis and chest
To help protect your hip for the first 6 weeks after
your total hip replacement.
Do not bend your operated hip more than 90. Don't
lean forward when
sitting, to reach anything!
Avoid sitting on low chairs, stools or toilets or in
car seats where your
knees are higher than your hips.
You should avoid crossing your legs or putting your
operated leg across
the midline of your body
You should avoid lying on the operated side but you
may be able to lie on
the opposite side with a pillow between your legs.
Avoid Crossing your legs
Avoid lifting heavy items
Avoid heavy housework
Avoid lying on the operated side
Avoid reaching towards your feet to dry them, put on
Risks of hip replacement surgery:
Any operation that requires a general anaesthetic has certain risks
attached to the
general anaesthetic. In addition, there are also small risks attached
to spinal or epidural anaesthesia. These risks will be discussed in
more detail with your anaesthetist but the
chances of having a major anaesthetic complication is uncommon.
As anybody undergoes general or regional anaesthesia
(epidural anaesthesia) there are
always risks associated with it. The risks of course are magnified if
you have abnormal
general medical conditions in addition to your older age, which may
have affected the
functions of your vital organs such as heart, lungs and kidneys.
Therefore a complete
evaluation of those systems has to be performed before you are taken
to the Operating
Specific risks for total hip replacement include the
Deep vein thrombosis and pulmonary embolus:
You are given medication (injections)
to thin your blood and prevent these complications. Other measures
include TED stockings
and calf compressors.
Infection: Superficial wound infections
may occur early on and deeper infections can occur
at a later stage. The incident of infection is less than 1%.
Infections are usually treatable with antibiotic treatment. You are
given antibiotics before the operation and for the first two days to
prevent infections from happening. Very rarely, if a joint has a deep
infection that cannot be controlled with antibiotic therapy, the joint
requires removal and a second joint re-implanted
at a later stage.
Leg length discrepancy: It is not unusual
for there to be up to 1cm leg length discrepancy following a Hip
replacement. This is quite easily tolerated. The reason there may be a
discrepancy is to ensure that the hip joint is appropriately tensioned
so that it does not
dislocate. Initially you may think that you have a longer leg but this
is often due to muscle contracture which over time will loosen up and
your leg lengths will even out.
Hip dislocation: The risk of hip
dislocation is usually less than 1 or 2%. Provided the
components are placed correctly and the appropriate post-operative
adhered to, it is unlikely that the hip will dislocate.
Fractured femur: Very rarely the femoral
bone may fracture at the time of surgery and
this is usually treated immediately. It is also uncommon to fracture
following a total hip
replacement unless you have been involved in a bad accident.
Loosening of the prosthesis: As
mentioned, over time the prosthesis may loosen if the
bone does not grow into it sufficiently or if the bearing surface
wears out to produce
areas around the prosthesis, leading to loosening. Should a prosthesis
it can be revised. If only the bearing surface wears out, then usually
only the bearing
surface requires revision which is a much smaller operation. Patients
who have metal
on metal articulating surfaces have a slightly higher metal iron level
in their blood. This
has been extensively researched over the past 30 years and there have
increased incidents of cancer or any other problems.
Damage to nerves and vessels: It is
unusual to damage any major nerves or blood
vessels following a hip replacement. However nerve palsy can develop
if the nerve is
stretched during surgery. Those with hip dislocations from childhood
are at higher risk
of nerve injury.
Haematoma: Occasionally a bleed may occur
around the hip joint following the operation
that may require drainage.
Scarring: Some patients tend to scar more
than others and it may be that the scar that
you have will be quite thickened (keloid).
Long-term swelling: Occasionally the
operated leg may remain a little swollen for a
number of months but in general this tends to resolve.
Trochanteric bursitis: Occasionally
following hip replacement surgery one can experience
inflammation at the side of the hip joint which usually settles with
either a cortisone injection or anti-inflammatories.
Joint stiffness: Very rarely extra bone
can form around your hip joint which will cause
it to stiffen up again (heterotopic ossification). This is usually
painless but may cause some stiffness.
What sports can you do following total hip
Tennis (doubles), golf, bowls, cycling, gentle snow skiing and
walking. It is not advisable to be running following a total hip
General advice after hip replacement surgery:
- You should have a regular check every two years with an x-ray.
- If you have had any major bowel, bladder or dental surgery,
should be given prior to the surgery.
- Metal prostheses can activate security alarms at airports.