HIP REPLACEMENT SURGERY PROCEDURE
Category: Orthopedic Surgery
Abstract : Between 200,000 and 300,000 hip replacement operations are performed in the United States each year, most of them in patients over the age of 60. According to the American Academy of Orthopaedic Surgeons (AAOS), only 5–10% of total hip replacements as of 2002 were in patients younger than 50. There are two reasons for this concentration in older adults. Arthritis and other degenerati
Between 200,000 and 300,000 hip replacement operations are performed in the United States each year, most of them in patients over the age of 60. According to the American Academy of Orthopaedic Surgeons (AAOS), only 5–10% of total hip replacements as of 2002 were in patients younger than 50.
There are two reasons for this concentration in older adults.
Arthritis and other degenerative joint disorders are the most common health problems requiring hip replacement, and they become more severe as people grow older. The second reason is the limited life expectancy of the prostheses used in hip replacements. Because THR is a complex procedure and requires a long period of recovery after surgery, doctors generally advise patients to put off the operation as long as possible so that they will not need to undergo a second operation later to insert a new prosthesis.
This demographic picture is changing rapidly, however, because of advances in designing hip prostheses, as well as changes in older Americans’ rising expectations of quality of life. Many people are less willing to tolerate years of pain or limited activity in order to postpone surgery. In addition, hip prostheses are lasting longer than those used in the 1960s; one study found that 65% of the prostheses in patients who had had THR before the age of 50 were still intact and functioning well 25 years after the surgery. A larger number of hip replacements are now being done in younger patients, and the operation itself is being performed more often. One expert estimates that the annual number of hip replacements in the United States will rise to 600,000 by 2015.
Description
Hip replacement surgery is a relatively recent procedure that had to wait for the invention of plastics and other synthetic materials to make reliable prostheses that could withstand years of wear. The first successful total hip replacement was performed in 1962 by Sir John Charnley (1911–1982), a British orthopedic surgeon who designed a device that is still known as a Charnley prosthesis. Charnley used a stainless steel ball mounted on a stem that was inserted into the patient’s thighbone to replace the femoral head. A high-density polyethylene socket was fitted into the acetabular side of the joint. Both parts of the Charnley prosthesis were secured to their respective sides of the joint with an acrylic polymer cement. More recent developments include the use of cobalt chrome alloys or ceramic materials in place of stainless steel, as well as methods for holding the prosthesis in place without cement.
As of 2003, there are three major types of hip replacement surgery performed in the United States: a standard procedure for hip replacement; a newer technique known as minimally invasive surgery (MIS), pioneered in Chicago in February 2001; and revision surgery, which is done to replace a loosened or damaged prosthesis.
Standard hip replacement surgery
A standard hip replacement operation takes 1-1/2–3 hours. The patient may be given a choice of general, spinal, or epidural anesthesia. An epidural anesthesia, which is injected into the space around the spinal cord to block sensation in the lower body, causes less blood loss and also lowers the risk of blood clots or breathing problems after surgery. After the patient is anesthetized, the surgeon makes an incision 8–12 in (20–30 cm) long down the side of the patient’s upper thigh. The surgeon may then choose to enter the joint itself from the side, back, or front.
The back approach is the most common. The ligaments and muscles under the skin are then separated.Once inside the joint, the surgeon separates the head of the femur from the acetabulum and removes the head with a saw. The surgeon uses a power drill and a special reamer to remove the cartilage from the acetabulum and shape it to accept the acetabular part of the prosthesis. This part of the new prosthesis is a curved piece of metal lined with plastic or ceramic.
After selecting the correct size for the patient, the surgeon inserts the acetabular component. If the new joint is to be cemented, the surgeon will attach the component to the bone with a type of epoxy. Otherwise the metal plate will be held in place by screws or by the tightness of the fit itself.
To replace the femoral head, the surgeon first drills a hollow inside the thighbone to accept a stem for the femoral component. The stem may be cemented in place or held in place by the tightness of the fit. A metal or ceramic ball to replace the head of the femur is then attached to the stem.
After the prosthesis is in place, an x ray is taken to verify that it is correctly positioned. The incision is then washed with saline solution as a safeguard against infection. The sutures used to close the deeper layers of tissue are made of a material that the body eventually absorbs, while the uppermost layer of skin is closed with metal surgical staples. The staples are removed 10–14 days after surgery.
Finally, a large triangular pillow known as a Charnley pillow is placed between the patient’s ankles to prevent dislocation of the hip during the first few days after surgery.
Minimally invasive hip replacement surgery
Minimally invasive surgery (MIS) is a new technique of hip replacement introduced in 2001. Instead of making one long incision, the surgeon uses two 2-inch (5 cm) incisions or one 3.5-1/2-inch (9 cm) incision. Using newly designed smaller implements, the surgeon removes the damaged bone and inserts the parts of the new prosthesis. MIS hip replacement takes only an hour and a half; there is less bleeding and the patient can leave the hospital the next day. As of 2002, however, obese patients or those with very weak bones are not considered for MIS.
Revision surgery
Revision surgery is most commonly performed to replace a prosthesis that no longer fits or functions well because the bone in which it is implanted has deteriorated with age or disease. Revision surgery is a much more complicated process than first-time hip replacement; it sometimes requires a specialized prosthesis as well as bone grafts from the patient’s pelvis, and its results are not usually as good. On the other hand, some patients have had as many as three revision operations with satisfactory results.
Diagnosis/Preparation
Because pain in the hip joint is usually a gradual development, its cause has been diagnosed in most cases by the time the patient is ready to consider hip replacement surgery. The doctor will have taken a careful medical and employment history in order to determine the most likely cause of the pain and whether the patient’s job may be a factor. The doctor will also ask about a family history of osteoarthritis as well as other disorders known to run in families. The patient will be asked about injuries, falls, or other accidents that may have affected the hip joint; and about his or her use of alcohol and prescription medications—particularly steroids, which can cause avascular necrosis.The patient will then be given a complete physical examination to evaluate his or her fitness for surgery.
Certain disorders, including Parkinson’s disease; dementia and other conditions of altered mental status; kidney disease; advanced osteoporosis; disorders associated with muscle weakness; diabetes; and an unstable cardiovascular system are generally considered contraindications to hip replacement surgery. People with weakened immune systems may also be advised against surgery. Inthe case of obesity, the operation may be postponed until the patient loses weight. The stress placed on the hip joint during normal walking can be as high as three times the patient’s body weight; thus each pound in weight reduction equals three pounds in stress reduction. Consequently, weight reduction lowers an obese patient’s risk of complications after the operation. The doctor will also order a radiograph, or x ray, of the affected hip. The results will show the location and extent of damage to the hip joint.
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