HIP & KNEE

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HIP REVISION

Source: American Academy of Orthopaedic Surgeons http://orthoinfo.aaos.org/topic.cfm?topic=A00355#Partial%20Hip%20Replacements

PARTIAL HIP REPLACEMENT

Whether you have just begun exploring treatment options or have already decided to undergo hip replacement surgery, this information will help you understand the benefits and limitations of partial hip replacement. This article describes how a normal hip works, the causes of hip pain, and an overview of what to expect from hip replacement surgery.

If your hip has been damaged by arthritis, a fracture, or other conditions, common activities such as walking or getting in and out of a chair may be painful and difficult. Your hip may be stiff, and it may be hard to put on your shoes and socks. You may even feel uncomfortable while resting.

If medications, changes in your everyday activities, and the use of walking supports do not adequately help your symptoms, you may consider hip replacement surgery. Hip replacement surgery is a safe and effective procedure that can relieve your pain, increase motion, and help you get back to enjoying normal, everyday activities.

First performed in 1960, hip replacement surgery is one of the most successful operations in all of medicine. Since 1960, improvements in joint replacement surgical techniques and technology have greatly increased the effectiveness of partial hip replacement. According to the Agency for Healthcare Research and Quality, more than 285,000 partial hip replacements are performed each year in the United States.

ANATOMY

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.

Normal hip anatomy
Normal hip anatomy

COMMON CAUSES OF HIP PAIN

The most common cause of chronic hip pain and disability is arthritis. Osteoarthritis, rheumatoid arthritis, and traumatic arthritis are the most common forms of this disease.

  • 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.
A hip with osteoarthritis
A hip with osteoarthritis.

DESCRIPTION

If only one part of the joint is damaged or diseased, a partial hip replacement may be recommended. In most instances, the acetabulum is left intact and the head of the femur is replaced, using components similar to those used in a partial hip replacement. The most common form of partial hip replacement is called a bipolar prosthesis. In a partial hip replacement (also called partial hip arthroplasty), the damaged bone and cartilage is removed and replaced with prosthetic components.

  • The damaged femoral head is removed and replaced with a metal stem that is placed into the hollow center of the femur. The femoral stem may be either cemented or “press fit” into the bone.
  • A metal or ceramic ball is placed on the upper part of the stem. This ball replaces the damaged femoral head that was removed.
  • A plastic, ceramic, or metal spacer is inserted between the new ball and the socket to allow for a smooth gliding surface.
Components of a hip replacement
(Left) The individual components of a partial hip replacement. (Center) The components merged into an implant. (Right) The implant as it fits into the hip.

CANDIDATES FOR SURGERY

There are no absolute age or weight restrictions for partial hip replacements.

Recommendations for surgery are based on a patient’s pain and disability, not age. Most patients who undergo partial hip replacement are age 50 to 80, but orthopaedic surgeons evaluate patients individually. Partial hip replacements have been performed successfully at all ages, from the young teenager with juvenile arthritis to the elderly patient with degenerative arthritis.

ORTHOPAEDIC EVALUATION

An evaluation with an orthopaedic surgeon consists of several components.

  • Medical history. Your orthopaedic surgeon will gather information about your general health and ask questions about the extent of your hip pain and how it affects your ability to perform everyday activities.
  • Physical examination. This will assess hip mobility, strength, and alignment.
  • X-rays. These images help to determine the extent of damage or deformity in your hip.
  • Other tests. Occasionally other tests, such as a magnetic resonance imaging (MRI) scan, may be needed to determine the condition of the bone and soft tissues of your hip.