出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/09/07 11:12:08」(JST)
| It has been suggested that Arthroplasty be merged into this article. (Discuss) Proposed since August 2014. |
| This article may require cleanup to meet Wikipedia's quality standards. No cleanup reason has been specified. Please help improve this article if you can. (June 2010) |
| Joint replacement | |
|---|---|
| Intervention | |
| ICD-10-PCS | 0?R?0JZ |
| ICD-9-CM | 81.5, 81.8 |
| MeSH | D019643 |
Replacement arthroplasty [from Greek arthron, joint, limb, articulate, + -plassein, to form, mould, forge, feign, make an image of], or joint replacement surgery, is a procedure of orthopedic surgery in which the arthritic or dysfunctional joint surface is replaced with an orthopedic prosthesis. Joint replacement is considered as a treatment when there is severe joint pain or dysfunction is not alleviated by less-invasive therapies.
Joint replacement surgery is becoming more common with knees and hips replaced most often. As of 2009, about 773,000 Americans have a hip or knee replaced each year".[1]
Stephen S. Hudack, a surgeon based in New York City, began animal testing with artificial joints in 1939.[2] By 1948, he was at the New York Orthopedic Hospital (part of the Columbia Presbyterian Medical Center) and with funding from the Office of Naval Research, was replacing hip joints in humans.[2]
Two previously[when?] popular forms of arthroplasty were: (1) interpositional arthroplasty', with interposition of some other tissue like skin, muscle or tendon to keep inflammatory surfaces apart and (2) excisional arthroplasty in which the joint surface and bone were removed leaving scar tissue to fill in the gap. Other forms of arthroplasty include resection(al) arthroplasty, resurfacing arthroplasty, mold arthroplasty, cup arthroplasty, and silicone replacement arthroplasty. Osteotomy to restore or modify joint congruity is also a form of arthroplasty.
In recent decades the most successful and common form of arthroplasty is the surgical replacement of a joint or joint surface with a prosthesis. For example, a hip joint that is affected by osteoarthritis may be replaced entirely (total hip arthroplasty) with a prosthetic hip. This procedure involves replacing both the acetabulum (hip socket) and the head and neck of the femur. The purpose of doing this surgery is to relieve pain, to restore range of motion and to improve walking ability, leading to the improvement of muscle strength.
Before major surgery is performed, a complete pre-anaesthetic work-up is required. In elderly patients this usually would include ECG, urine tests, hematology 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, implant design selecting and size-matching to the xray images (a process known as templating).
A few days' hospitalization is 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[1] 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, as the patients' muscles take time to heal after the surgery; exercises for range of motion of the joints and ambulation should not be strenuous. Later when the muscles have healed, the aim of exercise expands to include strengthening and recovery of function.
Some ceramic materials commonly used in joint replacement are alumina (Al2O3), zirconia (ZrO2), silica (SiO2), hydroxyapatite (Ca10(PO4)6(OH)2), titanium nitride (TiN), silicon nitride (Si3N4). A combination of titanium and titanium carbide is a very hard ceramic material often used in components of arthroplasties due to the impressive degree of strength and toughness it presents, as well as its compatibility with medical imaging.
Titanium carbide has proved to be possible to use combined with sintered polycrystalline diamond surface (PCD), a superhard ceramic which promises to provide an improved, strong, long-wearing material for artificial joints. PCD is formed from polycrystalline diamond compact (PDC) through a process involving high pressures and temperatures. When compared with other ceramic materials such as cubic boron nitride, silicon nitride, and aluminum oxide, PCD shows many better characteristics, including a high level of hardness and a relatively low coefficient of friction. For the application of artificial joints it will likely be combined with certain metals and metal alloys like cobalt, chrome, titanium, vanadium, stainless steel, aluminum, nickel, hafnium, silicon, cobalt-chrome, tungsten, zirconium, etc.[3]
In joints such as knee replacements there are two parts that are ceramic and they can be made of either the same ceramic or a different one. If they are made of the same ceramic, however, they have different weight ratios. These ceramic parts are configured so that should shards break off of the implant, the particles are benign and not sharp. They are also made so that if a shard were to break off of one of the two ceramic components, they would be noticeable through x-rays during a check-up or inspection of the implant. With implants such as hip implants, the ball of the implant could be made of ceramic, and between the ceramic layer and where it attaches to the rest of the implant, there is usually a membrane to help hold the ceramic. The membrane can help prevent cracks, but if cracks should occur at two points which create a separate piece, the membrane can hold the shard in place so that it doesn't leave the implant and cause further injury. Because these cracks and separations can occur, the material of the membrane is a bio-compatible polymer that has a high fracture toughness and a high shear toughness.[4]
The Stress of the operation may result in medical problems of varying incidence and severity.
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
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| リンク元 | 「人工関節」 |
| 関連記事 | 「join」「artificial」「joint」 |
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