Juvenile
chronic arthritis
In these patients the disability in other joints and the lack of demand
that they make on the hip replacement makes it the treatment of choice despite
their young age. Nevertheless, there are considerable technical difficulties;
these patients have all the complications of long-term steroid therapy and the
hip joint may be too small for normal implants because it was damaged with
arthritis before it had fully developed.
Hip
dysplasia
Patients with hip dysplasia may start to develop arthritis in their
teens or early 20s. X-rays will show subluxation of the hip joint which rides up
the deficient acetabular wall and there may already he signs of point loading on
the edge of the acetabulum with osteoarthritis starting to form. The treatment
of this condition is contentious but most surgeons would recommend some form of osteotomy
to try to obtain better cover for the femoral head. The purpose is to
spread the load of the hip joint over a larger articular surface, and so an
osteotomy on the acetabular side is the preferred technique. The whole acetabulum
can he detached from the rest of the pelvic ring and rotated so that
an adequate roof is produced. The operation is technically very difficult to
perform and there is a risk of causing complete avascular necrosis and
chondrolysis of the acetabular cartilage.
An alternative is to cut through the ileum immediately above the
acetabulum and to displace the acetabular inwards under this shelf, so creating
a new roof for the acetabular. This operation too is difficult to perform and,
given the rarity of the cases and the problems of finding matched controls,
there is no evidence that this operation or any other for that matter makes any
difference to the outcome of the hip. A third operation is to lift a wedge of
bone on a proximally based cortical pedicle and create a roof by packing bone
graft inside the wedge. This is the simplest of the operations hut the least
attractive from a biomechanical point of view. If these operations are
successful and a new roof is created for the acetabulum in one way or another
the secondary advantage of this type of surgery is that it makes total hip
replacement in the future much easier. Otherwise there are great difficulties in
setting the cup in the pelvis because there is no bony roof to provide support
for it.
Hip dysplasia
Pelvic
osteotomy spreads the load and may make total hip replacement easier
Osteoarthritis
secondary to trauma in the young adult
Young, fit adults put a great load on the total hip replacement and will
also have a life expectancy in excess of 30—40 years. They may be in severe
pain and will push hard for a total hip replacement having heard of the marvelous
results which can be obtained in the elderly. It is important to
explain to
them that the lifetime of the hip may be as little as 5 years in
a young patient and that subsequent revisions are likely to have an even shorter
life. The better option in the young fit patient is a hip arthrodesis. The
operation, if successfully performed, will completely remove pain and produce a
strong, stable hip. This should last their lifetime without further problems. It
is even possible to unpick an arthrodesis and replace it with a total hip
replacement if problems start in the other hip or in the knee below the
arthrodesis. The disability of a successful hip arthrodesis is slight. The
patient can walk and run, but can usually only climb ladders one step at a time.
The stiff hip does not apparently interfere with the ability to have sexual
intercourse or to have children, and the only time when it is particularly a
problem is when sitting in a chair. Because the hip is only fused in slight
flexion the patient may have to slump in a chair with the leg sticking out in
front. This posture can appear very irritating to fellow passengers in a bus if
they are not aware of the reason for it. Technically, the arthrodesis can be
difficult to perform, but with the advent of modern techniques (using cobra
plates) and bone graft a secure arthrodesis should be obtainable. It is
important to make sure that the hip is arthrodesed in a good position. The ideal
is neutral or slight abduction with some 20-30degree of flexion. It is all too easy
to let the hip slip into adduction when there will be unnecessary relative
shortening. If the hip is fixed in too much abduction then the leg is too long
and it may be difficult to obtain adequate swing through. However, there will be
some shortening from fixing the hip in a little flexion (to allow sitting) so a
little abduction may compensate for that.
Hip arthrodesis
• Produces a painless hip
• Does not wear out
• Can be replaced with a total hip replacement later
• Ideal for a young active patient
Secondary
osteoarthritis in the older patient or in a patient who has a disease in other
joints
Arthrodesis should not be considered in patients who already have back
problems or who have arthritis in other joints. In these cases it increases the
patient’s disability and may exacerbate the pain from osteoarthritis in the
other joints. An alternative in the older patient who is still too young for a
total hip replacement is the femoral osteotomy.
The
femur is divided in the intertrochanteric region and then fixed securely using a
dynamic hip screw or a plate. It has been suggested that the cause of the deep
pain in osteoarthritis is venous hypertension, and that the osteotomy relieves
this hypertension. This cannot be the only explanation as, radiologically,
there may be a dramatic improvement in the joint surface with apparent regrowth
of articular cartilage. One element of the osteotomy is to change the angle of
the femoral head so that a new area of little worn articular cartilage can be
brought to bear on the acetabulum.
If the osteotomy also shortens the femur slightly then the pelvis will
dip down in compensation and in effect the acetabulum will give more cover to
the femoral head and it too will bring a new area of articular cartilage into
the load-bearing zone. Femoral osteotomy gives a variable relief of pain from
osteoarthritis, but it is reasonable to offer the patient up to 5 years
of pain relief, and it may be much longer. There is nothing to stop a total hip
replacement being performed after an osteotomy, so the advantage of using an
osteotomy to buy time in a patient who is a little too young for a total hip
replacement makes this a very attractive option. The operation needs to be
planned carefully in advance with tracings made from the X-rays to decide
exactly what type of wedge, if any, is to he taken out of the femur. If the
femur is to be rotated as well then it is advisable to put pins into the femur
either side of the osteotomy so that the angle of rotation can be carefully
measured. The osteotomy is fixed with either a blade plate or with a dynamic hip
screw. If the fixation is secure then the patient should be able to weight-bear
partially using crutches immediately after surgery and can start full
weight-bearing at 3 months.
Indications for osteotomy in hip arthritis
• Young patients not suitable for total hip replacement
• Problems in more than one joint not suitable for arthrodesls
Total
hip replacement
Total hip replacement is the mainstay of treatment for osteoarthritis
and rheumatoid arthritis of the hip, and for patients over the age of 65 years
is the operation of first choice. In patients between the age of 55 and
65 years the pros and cons should be weighed up carefully against osteotomy.
Below the age of 55 years total hip replacement should only be undertaken
in exceptional circumstances and arthrodesis should be the treatment of choice.
Management of hip arthritis
• > 65 years — total hip replacement
• 55—65 years — osteotomy
• < 55 years — arthrodesis
Indications for surgery
The indications for an operation are primarily pain when it
can no longer can be controlled by using pain killers. A secondary indication is
interference with mobility and quality of life.
Types
of total hip replacement
There are nearly 100 different designs of total hip replacements
currently on the market and in almost none of them is there an adequate
long-term follow-up which a surgeon could use to decide which design to use (Fig.
23.8). Designs can be classified into some simple categories which are
given in Table 23.3 (see also Fig. 23.9).
Methods
of fixation
implant. There is currently no evidence whatsoever to support the use of
the more expensive and difficult to implant cementless implants, although
hydroxyapatite coating looks promising.
Joint
surfaces
The original total hip replacements designed by Charnley eventually used
a joint surface of metal on high-density polyethylene. The coefficient friction
between these two surfaces is far higher than articular cartilage, but because a
small head size was used the actual force on the implants remained low.
High-density polyethylene has good shock-absorbing properties but does wear
slowly over the years producing small particles which can stimulate an
inflammatory response in the joint. It is felt that this inflammatory response
can, once again, be responsible for aseptic loosening. The macrophagcs actually
start to resorb bone and may stimulate osteoclasts to do the same. There has
therefore been a move towards using joints which do not produce wear particles.
Ceramic femoral heads bearing on polythene cups have far lower friction, but
ceramic femoral heads on ceramic acetabular cups have the lowest friction of
all. They are, however, very difficult and very expensive to manufacture.
Metal-on-metal implants should also have a low coefficient of friction and
produce very few wear particles. These implants were frequently used in the
early days of joint replacement but had a bad reputation for loosening. It is
currently claimed that this was because they were not manufactured to a high
enough tolerance, and that the surfaces were binding together, loosening the
implant. There is as yet, however, no evidence that the newer metal-on-metal
implants offer anything but theoretical advantages.
Head
size
The original implants used a small head size of 22 mm to reduce friction
(Fig. 23.10). This has the added advantage of allowing plenty of room inside the
acetabulum for a thick polythene cup which has plenty of room for wear and which
should have good shock-absorbing capabilities. The small head, however, does
carry a theoretical higher risk of dislocation, because the diameter of the head
is so small that a relatively small displacement of the hip out of the socket
allows it to dislocate. Biomechanical calculations show that the load on the
polythene cup produced by a small head is close to the limits which can be
tolerated by the polythene, and
Choice
of implant
Currently, the best long-term results have been obtained with some of
the older and cheaper cemented implants. In good hands these implants should
give over 50 per cent of the patients a trouble-free joint for over 10 years. In
younger patients the figures are not so good, and once a joint has been revised
the lifetime of the second implant appears to be shorter. New designs (Fig.
23.11) should not be introduced on to the market without proper trials being
performed. Surgeons should be able to explain to their patients who will be
performing the operation, the published results of the design that they are
using and the ongoing results of the design in their own hands.
Surgical
technique
There are three commonly used approaches to total hip replacement. The
fact that there are three suggests that there are advantages and disadvantages
to each.
The
anterolateral approach
The anterolateral approach has been popularised by many surgeons,
particularly Hardinge. The patient can be positioned on the table either in the
lateral position or supine with a sandbag under the buttock to raise it clear
from the table. If the supine position is used then the patient needs to be
placed as close to the edge of the table as possible as otherwise access is
restricted. A 15-cm incision is centred over the greater trochanter curving 450
backwards above the greater trochanter and running straight down the line of
the femur below the greater trochanter. Tensor fascia lata is divided over the
greater trochanter and held apart with a self-retaining retractor. Gluteus
medius is divided off the front of the greater trochanter, until the capsule is
exposed. The fibres of gluteus medius are gently divided above the greater
trochanter for a few centimetres (no further or the neurovascular bundle may be
damaged). A sharp retractor can now he introduced over the capsule and the front
of the femoral head into the anterior wall of the acetabulum, taking care not to
damage the femoral nerve. The anterior capsule is divided removing as large an
ellipse as possible but taking care, particularly inferiorly, not to cut blind
into veins running in the soft tissue just outside the hip joint. The assistant
now takes the patient’s leg, bending the knee at right angles, and dislocates
the hip by external rotation. Great care should be taken not to use too much
force during this manoeuvre as otherwise the femur will be fractured. If the hip
cannot he dislocated safely then the femoral neck should be cut and then the
femoral head removed using a bone screw in the same way as the femoral head is
removed during surgery for a subcapital fractured neck of femur.
The
trochanteric approach
This is an important approach because it gives excellent access to the
hip, and is also a very useful approach for reconstruction of the pelvis after
pelvic fracture. However, in all but expert hands reattachment of the greater
trochanter after surgery has given significant complications. Nonunion of the
greater trochanter can be painful and weakens the hip considerably. The approach
should only be used after careful training.
The patient can be placed supine on the table and a straight or curved
incision made centred over the greater trochanter. Tensor fascia lata is divided
along the lines of its fibres and the soft tissue cleaned off the lateral side
of the femur and the greater trochanter. A Gigli saw is passed over the top of
the femoral neck beneath the insertion of the abductors and the greater
trochanter taken off with an oblique osteotomy continuing the line of the
femoral neck across the femur. Some people insert a Steinmann pin into the
lateral cortex of the femur to tent the Gigli saw so that an oblique
chevron-type osteotomy is performed. The hip can now be dislocated anteriorly.
Before the femoral component is cemented into place wires are laid in place
ready for reattachment of the greater trochanter.
T
The
patient is placed in the full lateral position and an incision is made centred
over the greater trochanter with the
Performing
the total hip replacement
The knee should be bent to 900 and the tibia placed either
horizontal or vertical in relation to the floor, so that you can be sure of the
orientation of the femoral shaft. If the femoral neck has not already been cur
it should now be cut at the correct level allowing 10-200 of ante version if it
is a posterior approach, slightly less ante version if it is antrochanteric or
anterolateral approach. The level of the cut on the femoral neck can be
determined by laying a trial prosthesis against the femur and marking where the
neck of the implant lies when the centre of the head is level with the centre of
the old femoral head. The femur now needs to be retracted out of the way of the
acetabulum taking care nor to damage the sciatic nerve or the femoral nerve with
the retractor. Further excision of the capsule may be necessary before the femur
is released adequately to do this. The ligamentum teres and any other soft
tissue is excised from the acetabulum.
The acetabulum is now reamed with a strawberry reamer pushed in along
the line that the acetabular cup will occupy when it is placed in the acetabulum.
Reaming should continue until the osteophytes around the central fovea have been
removed. The size of the strawberry reamer should be increased until it is just
gripping the edges of the old acetabulum. Reaming should be continued until
all the articular cartilage has been removed and subchondral bone is exposed.
Keyholes need to be drilled in the subchondral bone to provide extra support for
the cement, avoiding the weight-bearing superolateral area. The keyholes do not
need to be more than a couple of millimetres deep and should not broach the
medial wall. They are therefore best placed into the anterior and posterior
pillars. Choose the correct size of acetabular cup for the reamer that has been
used so that a thin mantle of cement will lie all the way around the implant.
Check that the acetabular cup when inserted will lie comfortably just inside the
acetabulum and that its superolateral margin is bearing on the superolateral
margin of the acetabulum when it is placed with 30-45o of cover and
10-20o of
anteversion. The acetabulum should then be packed with a dry swab and the
retractors removed.
The femur should now be rotated to expose the cancellous bone in the
femoral neck and to deliver the femur up and out of the wound so that rasps can
be inserted without touching the gluteal muscles or the skin. A sharp lever may
need to be inserted under the greater trochanter to help this. Spoon out the
medullary contents of the femur keeping the convex side of the spoon always
facing the dorsum of the femur. This will prevent the spoon inadvertently being
driven out through the lateral cortex of the femur. Clear out the cancellous
hone, particularly in the greater trochanter, until the spoon can be inserted
straight down the
The purpose of the trial reduction is to check the orientation of the
femur and the acetabulum, and to check that tension in the soft tissues is
adequate to stabilise the components but not so great that reduction will prove
impossible once cementing has been performed. If the reduction is satisfactory
mix the first batch of cement and, when it is no longer sticky but wrinkles when
compressed, change gloves and insert the cement into a clean, dry acetabulum.
Insert the chosen cup, apply pressure directly up the line of the cup allowing
for adequate cover and anteversion. Remove excess cement from around the cup,
particularly posteriorly. When the cement has set, check that all extraneous
cement has been removed and cover the acetabular component with a swab. Insert a
cement restrictor into the femoral canal. Wash out the femoral canal with
copious volumes of saline and then pack the canal with dry swabs and start
mixing the cement for the femoral canal using a cement gun. When the cement is
ready, remove the swabs and inject the cement into the femoral canal from the
bottom up. Insert the femoral component, ensuring that the rotation does nor
change as the implant is inserted and that the tip of the femoral component runs
down the centre of the canal, or even slightly medially. Continue to apply
pressure to the femoral component once it has bedded down, and remove all extra
cement.
When the cement has set check that all extra cement has been removed and
that there are no fragments lying loose in the wound. Reduce the implant and
test stability in full internal and external rotation in both full extension and
full flexion. Make a note if stability is compromised in any way so that
postoperative care can make allowance for this. Wash out the wound with copious
volumes of saline. If the sciatic nerve was visualised, check once again that it
is intact and undamaged. Close the muscles in layers over two drains, one deep
and one superficial.
Postoperatively, the patient should be managed in troughs or with an
abduction pillow to keep the legs slightly abducted. If there is gross
instability then a plaster spica may need to be applied, including the feet if
rotation needs to be controlled. After an uneventful total hip replacement the
patient can be mobilised as soon as resources are available. If the patient has
already been taught how to use crutches before surgery then mobilisation will be
much easier. The patient should avoid sitting on a low seat or on a lavatory
seat which has not been raised for at least 6 weeks after surgery as this
position invites dislocation. If social circumstances are satisfactory the
patient can be discharged home between day 7 and day 10. An annual review should
be performed for the rest of the life of the patient in order to gain
information about the natural history of total hip replacement and to identify
aseptic loosening early before there is too much damage to the bone. The results
of this annual review should be used to build up a bank of information on a
unit’s success with joint replacement. It should also be made available to any
national register so that long-term results on large numbers can be used to see
how the successful joint replacement process may be improved.
Prophylactic
antibiotics
There is good evidence that at least three doses of a broad-spectrum
antibiotic should be used to cover total hip replacement. If this is combined
with the use of laminar flow operating theatres, the chance of a total hip
replacement becoming infected should be less than 2 per cent. One dose
Thromboprophylaxis
The total death rate after total hip replacement is around nine deaths
per 1000 patients in the first 90 days. Three of those deaths would have
occurred in the normal population even if they had not had a total hip
replacement. Therefore the excess number of deaths is six people per 1000, i.e.
less than 1 per cent. Only a small proportion of those deaths is caused by
pulmonary embolus, the major cause of death being myocardial infarct and
stroke. There is no evidence that thrombopropylaxis affects the overall death
rate or, more particularly, the very low death rate for pulmonary embolus. There
is clear evidence that thrombopropylaxis reduces the rate of deep vein
thrombosis, but it is not clear whether this translates into a reduction in
pulmonary embolus or even postphlebitic limb. There has been little research
into the complications of thromboprophylaxis. Haematoma formation is
associated with an increased rate of infection but no studies have been
performed to determine whether thromboprophylaxis affects the infection rate
or, indeed, loosening of total hip replacements. There is also no evidence that
mechanical methods such as stockings or even foot pumps affect the death rate
after total hip replacement. There is some evidence that compression stockings
can, in fact, increase the instance of deep vein thrombosis. Despite the
prodigious efforts by the pharmaceutical industry to prove the efficacy of
thromboprophylaxis, there is as yet no evidence to support its use or, indeed,
to show that it does more harm than good. Therefore, under the present
circumstances there is no merit in using any form of thromboprophylaxis.
Consent
for total hip replacement
Consent for total hip replacement should involve, like any other
consent, checking what the patient knows about the operation after introductions
have been made. You should then explain to the patient exactly what the
operation involves. It is very helpful here to have a model of a hip replacement
for the patient to look at and to feel. Patients also like to be told where they
will be when they wake up, when they can first have visitors and when they are
likely to go home. You should then deal with the outcome of the operation in
terms of pain relief and mobility. The patient also needs a clear explanation of
the alternatives to the operation. In other words, what is the likely natural
history of their disease if they do not have surgery, as it is only if they have
the knowledge of the choices available to them that they can make an informed
decision. There are unlikely to be any variations to the operation under
anaesthetic and therefore these do not have to be described as they do in some
other operations, but the patient does need to have described to them the common
complications and the serious ones (Table
dislocation (2—5 per cent), damage to the sciatic or femoral
nerve (1—2 per cent), infection (1—2 per cent), fracture or penetration of
the femur (1—2 per cent), death from any causes (< 1 per cent). The patient
also needs to be warned that they may have an inequality of leg length after
surgery.
The patient needs to be warned that they are likely to receive a blood transfusion during the operation.
Postoperative
care
Most patients, especially males, are prone to urinary retention. If
they are not catheterised at surgery then they should be carefully observed
postoperatively. Nerve damage is one of the commoner complications. As soon as
the patient awakes a check should be made that there is no damage to the nerves
around the hip, especially the sciatic nerve. A simple test is to ask the
patient to dorsiflex the foot. The patient should be carefully nursed to avoid
flexion or adduction of the hip joint.
Revision
of total hip replacement
A significant number of total hip replacements now coming to operation
is revisions of primary total hip replacements which are loose. There are two
main causes for loosening. The first is sepsis and the second is aseptic
loosening (Fig. 23.12), possibly due to an inflammatory response secondary to
particle wear. A hip replacement, which is becoming loose develops increasing
pain. Septic loosening usually starts within months of the operation and the
history may give a clue to the problem. The patient may have had a persistent
discharge after surgery and pain relief may not have been complete. The organism
involved is usually a low-grade pathogen such as Staphylococcus epididymis. The
infection cannot be eradicated using antibiotics, but the symptoms may improve
if adequate doses of the correct antibiotics are used. A needle aspiration of
the synovial fluid may give a positive culture, but normally it is only at the
time of surgery that the diagnosis can be made. It is now normal to send tissue
for frozen section histology at the time of surgery. If signs of
infection are seen in the histology then the implant is assumed to be
loose because of infection.
Revision
of the infected total hip replacement
If it has been decided from preoperative aspiration or from frozen
section at surgery that the hip replacement is infected then further specimens
of the membrane surrounding the hip need to be sent for formal culture. Then,
and only then, should the patient be given the first dose of antibiotics. The
infective organism is likely to be a Staphylococcus and so it is normal
to give an antibiotic with good cover for this organism. Both femoral and
acetabular components are removed with all the cement. The acetabulum and
femoral canal are irrigated with saline and a further check is made that all
foreign material and fibrous membrane have been removed. A decision must be made
as to whether to insert gentamycin-impregnated beads and to leave the patient on
traction for 6 weeks without a hip joint to allow any infection to settle before
inserting a new implant (a so-called ‘two-stage revision’). The alternative
is to replace the joint at the same operation (a ‘one-stage revision). Either
way there is good evidence that the new implant should be put in using
antibiotic-inpregnated cement as this reduces the likelihood of a recurrence of
infection. A special revision implant may need to be used which may have a
longer stem (Fig. 23.13).
Management
of aseptic loosening
In this case a one-stage revision is performed. Some people would,
nevertheless, use an antibiotic-inpregnated cement in case an occult infection
had been missed. It is wise to take multiple bacteriological swabs of the
membrane around the hip before