Replacement joint: Wikis


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Joint replacement consists of replacing painful, arthritic, worn or cancerous parts of the joint with artificial surfaces shaped in such a way as to allow joint movement.

Arthroplasty [from Greek arthron, joint, limb, articulate, + -plassein, to form, mould, forge, feign, make an image of] is a procedure of orthopedic surgery, in which the arthritic or dysfunctional joint surface is replaced with something better or by remodelling or realigning the joint by osteotomy or some other procedure.

Contents

Background

Previously, a popular form of arthroplasty was interpositional arthroplasty with interposition of some other tissue like skin, muscle or tendon to keep inflammatory surfaces apart or excisional arthroplasty in which the joint surface and bone was removed leaving scar tissue to fill in the gap. Other forms of arthroplasty include resection(al) arthroplasty, resurfacing arthroplasty, mold arthroplasty, cup arthroplasty, silicone replacement arthroplasty, etc. Osteotomy to restore or modify joint congruity is also an arthroplasty.

For the last 45 years the most successful and common form of arthroplasty is the surgical replacement of arthritic or destructive or necrotic joint or joint surface with prosthesis. For example a hip joint that is affected by osteoarthritis may be replaced entirely (total hip arthroplasty) with a prosthetic hip. This would involve replacing both the acetabulum (hip socket) and the head and neck of the femur. The purpose of this procedure is to relieve pain, to restore range of motion and to improve walking ability, thus leading to the improvement of muscle strength.

Indications

Timeline

Because of the major surgery a complete pre-anaesthetic work-up is required. In elderly patients this usually would include ECG, urine tests, haematology and blood tests. Cross match of blood is routine also as a high percentage of patients receive a blood transfusion. Pre-operative planning requires accurate Xrays of the affected joint. The implant design is selected and the size matched to the xray images (a process known as templating).

A few days hospitalization followed by several weeks of protected function, healing and rehabilitation. This may then be followed by several months of slow improvement in strength and endurance.

Early mobilisation of the patient is thought to be the key to reducing the chances of complications such as venous thromboembolism and Pneumonia. Modern practice is to mobilize patients as soon as possible and ambulate with walking aids when tolerated. Depending on the joint involved and the pre-op status of the patient the time of hospitalization varies from 1 day to 2 weeks with the average being 4–7 days in most regions.

Physiotherapy is used extensively to help patients recover function after joint replacement surgery. A graded exercise programme is needed. Initially the patients' muscles have not healed after the surgery; exercises for range of motion of the joints and ambulation should not be strenuous. Later when the muscle is healed the aim of exercise expands to include strengthening and recovery of function.

Risks and complications

Medical risks

The Stress of the operation may result in medical problems of varying incidence and severity.

Intra-operative risks

  • Mal-position of the components
  • Fracture of the adjacent bone
  • Nerve damage
  • Damage to blood vessels

Immediate risks

Medium-term risks

Long-term risks

  • Loosening of the components: the bond between the bone and the components or the cement may break down or fatigue. As a result the component moves inside the bone causing pain. Fragments of wear debris may cause an inflammatory reaction with bone absorption which can cause loosening. This phenomenon is known as osteolysis.
  • Wear of the bearing surfaces: polyethylene is thought to wear in weight bearing joints such as the hip at a rate of 0.3mm per year. This may be a problem in itself since the bearing surfaces are often less than 10 mm thick and may deform as they get thinner. The wear debris may also cause problems.

There are many controversies. Much of the research effort of the orthopedic-community is directed to studying and improving joint replacement. The main controversies are

  • The best or most appropriate bearing surface - metal/polyethylene, metal-metal, ceramic-ceramic
  • Cemented vs uncemented fixation of the components
  • Minimally invasive surgery

See also

Specific joint replacements

Related treatents

References

External links








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