lunes, 30 de julio de 2012

The New Hip Replacement: MDM | Medical News and Health Information

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The New Hip Replacement: MDM | Medical News and Health Information

The New Hip Replacement: MDM -- Research Summary

BACKGROUND: The hip is one of the body's largest joints. It is a ball-and-socket joint. The socket is formed by the acetabulum, which is part of the large pelvis bone. The ball is the femoral head, which is the upper end of the femur (thighbone). The bone surfaces of the ball and socket are covered with articular cartilage, a smooth tissue that cushions the ends of the bones and enables them to move easily. A thin tissue called synovial membrane surrounds the hip joint. In a healthy hip, this membrane makes a small amount of fluid that lubricates the cartilage and eliminates almost all friction during hip movement. Bands of tissue called ligaments (the hip capsule) connect the ball to the socket and provide stability to the joint.
COMMON CAUSES: The five most common causes for hip pain are:
  • Osteoarthritis. This is an age-related "wear and tear" type of arthritis. It usually occurs in people 50 years of age and older and often in individuals with a family history of arthritis. The cartilage cushioning the bones of the hip wears away. The bones then rub against each other, causing hip pain and stiffness. Osteoarthritis may also be caused or accelerated by subtle irregularities in how the hip developed in childhood.
  • Rheumatoid arthritis. This is an autoimmune disease in which the synovial membrane becomes inflamed and thickened. This chronic inflammation can damage the cartilage, leading to pain and stiffness. Rheumatoid arthritis is the most common type of a group of disorders termed "inflammatory arthritis."
  • Post-traumatic arthritis. This can follow a serious hip injury or fracture. The cartilage may become damaged and lead to hip pain and stiffness over time.
  • Avascular necrosis. An injury to the hip, such as a dislocation or fracture, may limit the blood supply to the femoral head. This is called avascular necrosis. The lack of blood may cause the surface of the bone to collapse, and arthritis will result. Some diseases can also cause avascular necrosis.
  • Childhood hip disease. Some infants and children have hip problems. Even though the problems are successfully treated during childhood, they may still cause arthritis later on in life. This happens because the hip may not grow normally, and the joint surfaces are affected.
(Source: http://orthoinfo.aaos.org)
WIPING OUT PAIN: The Modular Dual Mobility (MDM) hip replacement uses a small metal or ceramic head that fits into a larger high- tech plastic head. The large plastic head then fits inside a smooth metal cup. Because of the large plastic head, the MDM renders the joint extremely stable so that active patients can engage in recreational and sports activities. The large head also allows a greater, more normal range of motion than standard implants. The small head moves within the plastic large head, and it in turn moves in the socket. This design is called a "dual mobility" cup.

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