Arthroplasty is the only effective therapy for coxarthrosis. Surgery replaces the diseased joint and eliminates arthritic pain.
The hip replacement is the only possible therapy in cases of advanced degeneration of the joint.
The operation replaces the femur head and acetabulum with artificial components that reproduce all the movements of the affected joint as faithfully as possible.
The prosthesis is made up of the following components:
• a cup-form cotyle, replacing the acetabulum, inserted in direct contact with the bone;
• a cotyle insert anchored to the inner wall of the cotyle, thus forming one of the prosthesis’s two articular surfaces, so that, being concave, it can “accommodate” the femur head fixed to the stem;
• a femur head (or “head”), fixed to the stem to articulate (thanks to its spherical shape) with the cotyle insert;
• a stem that fits into the femoral channel and integrates with the bone; it is fixed to the prosthesis head in the proximal part.
Hip replacement – a routine operation in specialist clinics – involves the removal of the worn out cartilage in the acetabulum to prepare the portion of bone that will house the cotyle. The cotyle is then positioned inside the acetabulum so that it acts as a “lining” of the old bone surface.
The second phase of the operation is to remove the consumed femur head and position the stem that will articulate with the cotyle to form the new joint inside the femoral channel.
This is a total hip replacement as opposed to a partial arthroprosthesis or endoprosthesis, in which only the femur head is removed. An endoprosthesis operation is indicated in the case of fractures to the femur neck when the cartilagineous surface is still healthy but the fractured bone is unlikely to heal. In this case it is sufficient to replace only the fractured part, ie. the neck and head the femur, with a stem whose head will articulate with the healthy acetabulum.
Although hip replacement operations, if carried out by specialized surgeons, solve the problem of arthritic pain and in a large majority of cases show successful outcomes, they may involve complications, as in all surgical operations, requiring continuation of therapy.
The most unpleasant immediate event is dislocation of the components. In this case the prosthetic head “exits” its housing (cotyle) due to a movement of the joint. This is why patients are instructed to avoid movements that risk dislocation for the first weeks after the operation while the tissues around the implant are healing.
Perioperative preventive antibiotics are always administered, so infections are very infrequent. Should they occur, however, therapies here too will have to be continued.
DURATION OF IMPLANT
Many studies have shown that most implants can last even up to 20 years from the first operation.
It is inevitable, however, that in the long term there will be a loosening (or mobilization) of the main components of the prosthesis (cotyle and stem) provoking pain in the prosthesized hip. This may be caused mechanically, due to a lack of osteointegration between the host bone and the prosthesis, or biological, due to wear of the prosthetic component. Wear causes the formation of foreign-body tissue around the prosthesis that will erode the bone around the implant.
Periodical clinical and radiographic control of the prosthesized hip is useful for picking up initial signs of mobilization and preventing the serious bone damage that a loosened prosthesis may cause by its movements.
In the event of mobilization of one or both components, they may be removed and replaced with a new prosthesis (prosthetic revision). For complex revision operations, orthopaedic surgeons are provided with special prosthesis models to remedy the shortage of bone preventing the implant of a traditional prosthesis.
Other factors causing a hip replacement to fail include recurrent dislocation of the prosthesis (which may provoke instability of the implant or wear of the cotyloid component), breakage of a component of the prosthesis following a violent trauma or minor but repeated traumas, or bone fracture, whether of the cotyle or (more frequently) the femur.
Hip replacement: radiography taken 19 years after implantation
1. COTYLE integrated with the acetabular bone.
2. Polyethylene INSERT fixed to the cotyle (polyethylene being radiotransparent and not visible to X-rays, it is rendered identifiable by a metal thread in the edge of the insert).
3. Spherical ceramic HEAD fixed to the stem.
4. Prosthetic STEM integrated with the femoral bone.
Detailed below are a number of precautions to take in the post-operative phase to avoid dislocation of the prosthesis in the first 6 weeks after a hip replacement operation and until the soft tissues have become stabilized. It is important in this delicate phase to comply with the doctor’s recommendations.
- Going home:
In a car it is advisable to use the back seat (in 4-door cars) and recline the seat to a comfortable position, with one or two cushions behind the head or shoulders to avoid affossarsi. In the case of a 2-door car, sit in the front with two cushions and the seat reclined to reduce flexion of the hip to a minimum.
- A litter picker stick should be used so as not to bend excessively forward; the hands should never reach below the level of the knees.
- When getting up, do not lean forward in the chair: first move the hips forward, then get up. In general, make sure the shoulders are not ahead of the hips when sitting down or getting up.
- Use a device to grip the blankets when in bed, don’t bend forward to reach them.
- Don’t cross the legs when sitting, standing or supine.
- Don’t sit on toilets or seats that are too low. Use a toilet riser and raise low seats with cushions. Continue to use a toilet riser after leaving hospital and for as long as the doctor instructs (around 6-10 weeks).
- In bed, place a cushion between the legs and keep them slightly flexed; this is because the legs must not cross or turn inwards.
- Don’t stand with feet turned inwards; when sitting, don’t allow the knees to turn inwards.
- When sitting, keep the knees apart.
- Don’t lie on the operated side until the doctor decides it is possible.
- Don’t cross the legs when walking and especially not when turning.
- Avoid sitting in positions in which the knees are higher than the hips.
- Don’t try getting into the bath without a bath seat; it’s best to be helped by someone anyway.
- Continue to use crutches or a walker for as long as instructed by the doctor.
- Avoid sitting for more an hour without getting up or doing some stretching.
- It’s possible to start driving again six weeks after the operation only if effective control of the operated hip has been regained and if the foot can be moved from accelerator to the brake with minimum effort.
- At night, lie in the part of the bed corresponding to the healthy limb (the right hand side of the bed if the left limb is the operated one). Avoid turning the trunk towards the side of the operated limb, which would be like turning the limb inwards.
- Try lying down in bed without a pillow for at least 15-30 minutes a day to prevent the onset of rigidity in the anterior part of the hip.
- If you think that the swelling of the limb has increased since returning home, try raising the foot (remembering to lean back). If the swelling persists, contact your doctor. Also call the doctor if you feel pain in the calf. It should be remembered that until full weight can be rested on the limb, the muscles cannot perform their pumping function, so the leg will tend to swell until capable of taking the full load. Swelling usually disappears at night.
- Going upstairs: lead with the healthy leg, keeping the crutches on the step below until both legs are on the step above, then bring up both crutches onto the step. Lean against the handrail if possible.
- Going downstairs: put the crutches on the step below, lead with the operated leg and follow with the healthy leg. Here too, lean against the handrail if possible.
- Long-term use of a crutch or stick in the hand opposite the operated side is advisable to minimize the forces acting daily on the hip prosthesis and to lengthen the life of the implant.
The rehabilitation period varies from case to case. On completion of the rehabilitation programme patients can normally carry out most day-to-day activities. Patients may resume normal sexual activity 4/6 weeks from the operation, depending on circumstances. The therapist and doctor will explain which positions do not put the implant at risk.
Work may be resumed either as beforehand or in an adapted form depending on the operation carried out and the type of occupation.
Sport may only be resumed with great care, because certain repeated movements may favour wear of the implant. Many activities are compatible with a hip replacement however. Detailed in the table below are the activities recommended in the long term following a total hip or knee replacement.
|Very good, highly recommended||Good, recommended||Requiring certain abilities, previous experience||With care, subject to doctor’s advice||Avoid|
|Dancing||Rower||Horse riding||Jazz dancing||Football|
|Golf||Speed walking||Ice skating||Tennis(doubles)||Softball|
|Sci da fermo||Table tennis||Stepper (with hip prosthesis, not knee)||Handball|
|Skiing (downhill)||Tennis (singles)|
|From DeAndrade RJ: Activities after replacement of the hip or knee. Orthop Special Ed 2:8, 1993.|
The information provided above does not constitute medical consulting in lieu of a doctor’s opinion. It may under no circumstances substitute the consulting, examination or diagnosis of a doctor.
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