Orthopaedic Specialists of Conneticut

Joint Replacement

Total Hip Replacement

What is it?

Total hip replacement is a surgical procedure for replacing the hip joint. This joint is composed of two parts--the hip socket (acetabulum, a cup-shaped bone in the pelvis) and the "ball" or head of the thigh bone (femur).

What can be expected of a total hip replacement?

A total hip replacement will provide complete or nearly complete pain relief in 90 to 95 percent of patients. It will allow patients to carry out many normal activities of daily living. The artificial hip may allow you to return to active sports or heavy labor under your doctor's instructions. Most patients with stiff hips before surgery will regain near-normal motion, and nearly all have improved motion.

There are many conditions that can result in degeneration of the hip joint . Osteoarthritis is perhaps the most common cause for hip replacement surgery. This condition is commonly referred to as "wear and tear arthritis". Osteoarthritis can occur with no previous history of injury to the hip joint - the hip simply "wears out". There may be a genetic tendency in some people that increases their chances of developing osteoarthritis.

Avascular necrosis is another cause of degeneration of the hip joint. In this condition, the femoral head (the ball portion) looses a portion of its blood supply and actually dies. This leads to collapse of the femoral head and degeneration of the joint. Avascular necrosis (AVN) has been linked to alcoholism, hip fractures, and dislocations of the hip, and long term cortisone treatment for other diseases.

Abnormalities of hip joint function resulting from fractures of the hip and some types of hip conditions that appear in childhood can also lead to degeneration many years after an injury. The mechanical abnormality of the joint causes excessive wear and tear - just like the out-of-balance tire of a car that wears out too soon.

Hip

Symptoms

The symptoms of a degenerative hip joint usually begin as pain when bearing weight on the affected hip. One may limp, which is the body's way of reducing the forces that the hip has to deal with. The degeneration will leads to a reduction in the range-of-motion of the affected hip. Bone spurs usually develop which limit movement of the hip joint. Finally, as the condition becomes worse, the pain may be present all the time and may keep one awake at night.

Diagnosis

The diagnosis of a degenerative hip joint starts with a complete history and physical examination by the doctor. X-rays are taken to determine the extent of the degenerative process and suggest a cause for the degeneration. Other tests may be required if there is reason to believe that other conditions are contributing to the degenerative process. Magnetic Resonance Imaging Scanning may be necessary to determine whether avascular necrosis is causing the hip condition. Blood tests may be required to rule out systemic arthritis or infection in the hip.

Medical Treatment

Not all hip conditions require a hip replacement as the initial treatment. We may suggest several alternative treatments to put off replacing the hip as long as possible. Using a cane may help alleviate some of the pain and allow to walk more comfortably. Anti-inflammatory medications may reduce the inflammation from the arthritis and reduce the pain.

Surgery

Most degenerative problems will eventually require replacement of the painful hip joint with an artificial hip joint, called prosthesis. Once the decision to proceed with surgery is made, there are several things to be done. A complete physical examination is done by a medical or family doctor. This is to ensure that the patient is in the best possible condition to undergo the operation. The patient may also need to spend time with a Physical Therapist who will be managing the rehabilitation after the surgery. The therapist may begin the teaching process before the surgery to ensure that the patients are ready for the rehabilitation afterwards.

The Artificial Hip Joint, called a prosthesis

There are two major types of artificial hip joint:

  • Cemented Prosthesis
  • Uncemented Prosthesis

Both types are widely used. The type of prosthesis used for the surgery is usually decided upon by the surgeon based on the age, lifestyle. Each prosthesis is made up of two parts:

  • The acetabular component, or socket portion, which replaces the acetabulum.
  • The femoral component, or stem portion, which replaces the femoral head.

The femoral component is made of a metal stem with a metal ball on the end. Some prosthesis has a ceramic ball attached to the metal stem. The acetabular component is a metal shell with a plastic inner socket liner that acts like a bearing. The type of plastic used is very tough and very slick - so slick and tough that you could ice skate on a sheet of the plastic without much damage to the plastic. A cemented prosthesis is held in place by a type of epoxy cement that attaches the metal to the bone.

An uncemented prosthesis has a fine mesh of holes on the surface area that touches the bone. The mesh allows the bone to grow into the mesh and "become part of" the bone.

hip replacement process

Complications of Total Hip Replacement

As with all major surgical procedures, complications can occur. The most common complications following hip replacement are:

  • Thrombophlebitis
  • Infection in the joint
  • Dislocation of the joint
  • Loosening of the joint

This is not intended to be a complete list of the possible complications, but these are the most common.

Thrombophlebitis
Thrombophlebitis, sometimes called Deep Venous Thrombosis (DVT), can occur after any operation. It is more likely to occur following surgery on the hip, pelvis, or knee. DVT occurs when the blood in the large veins of the leg forms blood clots within the veins. This may cause the leg to swell and become warm to the touch and painful. If the blood clots in the veins break apart they can travel to the lung. Once in the lung they get lodged in the capillaries of the lung and cut off the blood supply to a portion of the lung. This is called a pulmonary embolism. Pulmonary means "lung". An embolism is a fragment of something traveling through the vascular system. Most surgeons take preventing DVT very seriously. There are many ways to reduce the risk of DVT, but probably the most effective is getting the patient moving around as soon as possible!
Some of the commonly used preventative measures include:
  • Pressure stockings to keep the blood in the legs moving.
  • Medications that thin the blood and prevent blood clots from forming
Infection
Infection can be a very serious complication following an artificial joint replacement. The chance of getting an infection following total hip replacement is probably around 1 in 100 total hip replacements. Some infections may show up very early - before the patients leave the hospital. Others may not show up for months, or even years, after the operation.
Dislocation
Just like the real hip, an artificial hip can dislocate. Dislocation is when the ball comes out of the socket. There is a greater risk of dislocation right after surgery, before the muscles and tendons around the new joint have healed. However, there is always a risk of dislocation.
The therapist will carefully instruct the patient on how to avoid activities and positions which increase the risk of hip dislocation. A hip that dislocates more than once may have to be revised, which means another operation, to make the joint more stable.

How do artificial hips stand up over time?

The major long-term problems are loosening or wear. Loosening occurs either because the cement crumbles (as old mortar in brick building) or because the bone melts away (resorbs) from the cement. By 10 years, 25 percent of all artificial hips will look loose on an X-ray. Somewhat less than half of these (about 5% to 10% of all artificial hips) will be painful and require revision. Wear can occur in the plastic socket after some years. Small wear particles can cause inflammation resulting in thinning of the bone and risk of fracture.

Loosening and wear are in part related to how heavy and how active the patient is. It is for this reason we do not operate on very obese patients or young, active patients. Loose, painful artificial hips can usually, but not always, be replaced. The results of a second operation are not as good as the first, and the risks of complications are higher.

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