Joint replacement

From Wikipedia, the free encyclopedia

Joint replacement is one of the most common and successful operations in modern orthopaedic surgery. It 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.

Prognosis is good to excellent in 95% of major joint replacements (hips and knees). Pain relief is especially reliable. Full recovery of range of motion is not always accomplished.

Contents

[edit] Timeline

[edit] Pre-operative work-up

Because of the major surgery a complete pre-anaesthetic work-up is required. In elderly patients this usually would include ECG, Chest Xray, urine tests, haematology and biochemistry 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).

[edit] Recovery

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.

[edit] Post-operative rehabilitation

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.

[edit] Risks and complications

[edit] Medical risks

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

[edit] Intra-operative risks

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

[edit] Immediate risks

[edit] Medium-term risks

[edit] Long-term risks

  • Loosening of the components: the bond between the bone and the components or the cement may breakdown 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.

A comprehensive analysis of bodily tissues, including bone, shall soon hold promise for artificial joint replacement surgery. Currently, artificial joints utilize dissimilar junctions such as metal/bone, cement/bone, screw/bone; technology for such dissimilar tissue unions is improving, however these unions are certainly worse than a natural bone/bone junction. An emerging science, soon to be known as Advanced Tissue Welding, will address many of the union-related concerns pertaining to artificial implants. Bone is expected to be the most straightforward organic/artificial Tissue Weld to solve. By eliminating stress concentrations associated with metal/bone junctions and de-bonding concerns brought about by current cement/bone technology, advanced-matrix materials are anticipated to ossify (calcify into bone) more readily than a bone/bone junction.

  • 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.

Organic Tissues, including 3 types of cartilage, have the ability to regenerate and reshape over their use, while maintaining their design-intent. Through compressive dehydration and vacuum re hydration, organic cartilage maintains flexibility, lubrication and overall shape. It is anticipated that several solutions to degenerative joints and surrounding bone may exist, the last resort of which is artificial implant replacement. A hydrostatic joint fed by surrounding organic fluids shall eliminate wearing concerns of current polyethylene designs. However, existing joint tissues may be chemically, electrically and thermally manipulated to regenerate to their original function. Bone-spurring may be either surgically removed & prevented with a de-osseous technique, or advanced diet may assist in re-modeling the bone surrounding a joint. High-resolution injection therapy will assist in regenerating the concerning tissues (cartilage, tendons & ligaments).

[edit] Controversies

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

[edit] See also

[edit] References

 This article does not cite any references or sources. (May 2008)
Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed.

[edit] External links

v • d • e
Orthopedic surgery, operations/surgeries and other procedures on the musculoskeletal system (ICD-9-CM V3 76-84)
Bones
Joints
Muscle, tendon, fascia, and bursa
Other