Total Hip Replacement ( Total Hip Arthroplasty)

A painful hip can severely affect your ability to lead a full active life. Over the last 25 years, major advancements in hip replacement have improved the outcome of the surgery greatly. Hip replacement surgery is becoming more and more common as the population of the world begins to age.

Causes For Hip Replacement
There are many conditions that can result in degeneration of the hip joint (image). 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, 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 on your car that wears out too soon.

Symptoms
The symptoms of a degenerative hip joint usually begin as pain when bearing weight on the affected hip. You may limp, which is the body’s way of reducing the forces that the hip has to deal with. The degeneration will lead to a reduction in the range-of-motion of the affected hip. Bone spurs will 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 you awake at night.

Diagnosis
The diagnosis of a degenerative hip joint starts with a complete history and physical examination by your doctor. Xrays will be 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. MRI Scanning may be necessary to determine whether avascular necrosis is causing your 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. Your doctor may suggest several alternative treatments to put off replacing the hip as long as possible. Using a cane may help alleviate some of your pain and allow you to walk more comfortably. Anti-inflammatory medications may reduce the inflammation from the arthritis and reduce your pain.

Surgery
Most degenerative problems will eventually require replacement of the painful hip joint with an artificial hip joint, called a prosthesis. The decision to proceed with surgery should be made jointly by you, your family, and your doctor only after you feel that you understand as much about the procedure as possible.

Once the decision to proceed with surgery is made, there are several things to be done. Your orthopedic surgeon may suggest a complete physical examination by your medical or family doctor. This is to ensure that you are in the best possible condition to undergo the operation. You may also need to spend time with a Physical Therapist who will be managing your rehabilitation after the surgery. The therapist may begin the teaching process before the surgery to ensure that you are ready for the rehabilitation afterwards.

Finally, you may be asked to donate some of your blood before the operation. This blood can be donated once a week beginning about three to five weeks before the surgery. Your body will make new blood to replace the donated blood. If you need to have a blood transfusion at the time of surgery, you will receive your blood that has been stored in the blood bank.

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 your surgery is usually decided upon by your surgeon based on your age, your lifestyle, and the surgeon’s past experience.

Each prosthesis is made up of two parts (image):

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

The femoral component (image) is made of a metal stem with a metal ball on the end. Some prosthesis have a ceramic ball attached to the metal stem. The acetabular component (image) 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 (image) is held in place by a type of epoxy cement that attaches the metal to the bone. An uncemented prosthesis (image) 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.

The Operation
The steps for replacing the hip begin with making an incision about 8 inches long over the hip joint. There are several different approaches used to make the incision, usually based on your surgeon’s training and preferences.

After the incision is made, the ligaments and muscles are separated to allow the surgeon access to the bones of the hip joint. It is this part of the surgery that makes the ligaments and muscles somewhat weak after surgery. Until they heal, which takes about a month to six weeks, you must follow special hip precautions to prevent dislocation of your new hip joint.

Removing the Femoral Head (image)

Once the hip joint is entered, the femoral head is dislocated from the acetabulum. Then the femoral head is removed by cutting through the femoral neck with a power saw.

Reaming the Acetabulum (image)

After the femoral head is removed, the cartilage is removed from the acetabulum using a power drill and a special reamer. The reamer forms the bone in a hemispherical shape to exactly fit the metal shell of the acetabular component. The the new socket is inserted.

Inserting the Femoral Component (image)

A trial component, which is an exact duplicate of your hip prosthesis, is used to ensure that the joint you receive will be the right size and fit for you. Once the right size and shape is determined for the acetabulum, the acetabular component is inserted into place. In the uncemented variety of artificial hip replacement, the metal shell is simply held in place by the tightness of the fit or with screws to hold the metal shell in place. In the cemented variety, a special epoxy type cement is used to “glue” the acetabular component to the bone.

Preparing the Femoral Canal (image)

To begin replacing the femoral head, special rasps are used to shape and hollow out femur to the exact shape of the metal stem of the femoral component. Once again, a trial component is used to ensure the correct size and shape. The surgeon will also test the movement of the hip joint.

Inserting the Femoral Stem (image)

Once the size and shape of the canal exactly fit the femoral component, the stem is inserted into the femoral canal. Again, in the uncemented variety of femoral component the stem is held in place by the tightness of the fit into the bone (similar to the friction that holds a nail driven into a hole drilled into wooden board – with a slightly smaller diameter than the nail). In the cemented variety, the femoral canal is rasped to a size slightly larger than the femoral stem. Then the epoxy type cement is used to bond the metal stem to the bone.

Your surgeon will make every effort to maintain the leg length that you had before surgery, but there is no guarantee. Once you are up and walking around, you may find that your leg is now a fraction of an inch longer or shorter than it was before surgery.

Attaching the Femoral Head (image)

The metal ball that replaces the femoral head is attached to the femoral stem.

The Completed Hip Replacement (image)

You now have a new weight bearing surface to replace your diseased hip. Before your incision is closed, an x-ray is made to make sure your new prosthesis is in the correct position.

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 you 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 you leave the hospital. Others may not show up for months, or even years, after the operation. Also, an infection can spread into the artificial joint from other infected areas. Your surgeon may want to make sure that you take antibiotics when you have dental work, or surgical procedures on your bladder or colon to reduce the risk of spreading germs to your new joint.

Dislocation
Just like your 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 you 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.

Loosening
The major reason that artificial joints eventually fail continues to be loosening of the joint where the metal or cement meets the bone. There have been great advances in extending the life of an artificial joint. Still, most joints will eventually loosen and require a revision. Hopefully, you can expect 12-15 years of service from your artificial hip. In some cases the hip will loosen earlier than that. Just like your diseased hip, a loose joint causes pain. Once the pain becomes unbearable, another operation will probably be required to replace the hip.

Tags: special hip precautions, hip replacement surgery, Total Hip Replacement, Hip Replacement, hip surgery