Alternatives to total hip replacement

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

  Traditionally, hip replacements were fixed into a bed of polymethyl methacrylate (PMMA) cement. The cement is a grooting agent, in other words it acts as a spacer between the implant and the irregularly shaped cavity into which it is being put. A powder of PMMA cement is mixed with the monomer which is itself quite toxic to both patient and staff. The two are mixed together until an exothermic reaction starts and the cement begins to set. This takes 5—7 minutes. The cement is then put into the cavity and the implant pushed in on top of the cement until it is properly bedded in. Over the next 10 minutes the cement sets, becoming quite hot as it does so. The cup is cemented into place first. The process is then repeated with the femoral component. As the cement sets, some of the methyl methacrylate polymer is released into the patients blood stream and can cause a drop in the patient’s blood pressure. The heat produced by the cement setting may cause a layer of bone necrosis around the cement and it has been suggested that this may lead to early loosening. If fragments of the cement break away and get into the joint they will act as an abrasive and cause third-body wear. This destroys the artificial joint surface and releases a large amount of debris, which then sets up an inflammatory reaction. If the cement around the implant breaks or becomes loose it too will release particles which stimulate an inflammatory response. This too can lead to resorption of hone around the implant. This is called aseptic loosening as there is no evidence that infection has any role in this type of loosening. In response to these findings surgeons have attempted to design implants which can be fixed into the bone without the use of PMMA cement. In dentistry there has been considerable success with bone bonding to implants made of titanium for osseous integration and those which are coated in a layer of hydroxyapatite ceramic. Unfortunately, in joint replacement surgery this success has not been reproduced. Implants designed for cementless implantation are much more expensive to manufacture and need to be fitted much more carefully is there is to be any chance of good binding between the bone and the implant. Once they have been implanted the load on the interface should be kept to a minimum until osseous integration has had a chance to take place. Unfortunately, if this ever occurs it is likely to take many months, and even if a patient does not weight-bear during that time the micromovement between implant and bone may prevent osseous integration. This is because the hip joint is a fulcrum to powerful muscles around the hip. Even lifting the leg up off the bed may produce loads through the hip joint of three or four times body weight. One further practical advantage of cementless joint replacement is that when these implants do come loose, they should be easier to change as there is no need to remove all the cement from inside the femoral canal. Unfortunately, this too is only a theoretical advantage. Cementless hip replacements which start loosening and become painful may, nevertheless, have small areas where osseous integration has occurred. This can make them quite as difficult to remove as a cemented

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 therefore recently manufacturers have been moving towards a larger size of femoral head. The disadvantage of this increased head size is that the friction increases and so the force on the interface between the acetabular cup and the bone will be increased. Theoretically, this will increase the chance of loosening.

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.

The posterior approach to the hip This approach is quick and easy. Access is good but there is an increased risk of posterior dislocation after surgery.

The patient is placed in the full lateral position and an incision is made centred over the greater trochanter with the   upper arm curving backwards at 450 and the lower arm passing straight down the femur. Tensor fascia lata is divided along the line of its fibres and retracted. The hip is internally rotated by the assistant holding the lower leg. This exposes the short external rotators of the hip. The sciatic nerve runs over these muscles and should be identified and carefully retracted. The short external rotators are then divided on stay sutures and are folded back over the sciatic nerve to protect it. The capsule is now divided; a wide ellipse may be needed to be taken before the hip can be dislocated. Alternatively, an H-shaped incision can be made so that the capsule can be repaired once the hip replacement has been performed.

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 femoral canal. Insert rasps into the femoral canal, always applying pressure so that the shoulder of the rasp is pressing back against the greater trochanter and the tip is pressing towards the medial cortex of the femur. Once again, this will avoid the all too common complication of the rasp penetrating the lateral cortex of the femur. Continue rasping until a trial prosthesis can be inserted into the femur and lies comfortably with the tip resting against the medial cortex of the femur. Wrap a swab around the neck of the trial component and carry out a trial reduction with a trial acetabulum in place.

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 of the antibiotics should be given at induction and the other two doses to cover the next 24 hours. There is no evidence that giving antibiotics for any longer than this confers any added benefit.

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 23.4). In British law it is usually accepted that any complica­tion more common than 1 per cent needs to be described to the patient. In the case of total hip replacement the risks are:

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   prophylactic antibiotics are given. Postoperatively, there is a much higher risk of dislocation and it is normal to keep the patient in bed for several days and then to mobilise with great care. Before embarking on this operation patients need to be consented for the possibility that they may wake up without a hip replacement (the Girdlestone operation).