Hip Replacement Surgery Steps

Hip arthritis is a common cause of hip pain. If hip arthritis becomes severe, a hip replacement procedure may be recommended. Hip arthritis causes the normal smooth cartilage surface of the joint to wear out over time. As this cartilage is worn away, bone is exposed and normal movements of the hip become difficult. This can cause difficulty with activities including walking, getting up from a chair, or even sleeping at night.

The hip joint is a ball-and-socket joint -- the ball rotates within the socket to allow hip movement. The ball and the socket are covered with a layer of smooth cartilage. This cartilage allows for the hip joint to move freely. When the cartilage lining of the joint wears out, hip movements become stiff and painful.

The first step of a hip replacement surgery is to remove the damaged cartilage and bone. The hip joint has two sides, a ball (the femoral head), and the socket (the acetabulum). When the hip joint becomes arthritic, the normally smooth cartilage surface is worn away.

To remove the worn out ball of the ball-and-socket hip joint, the bone is cut to remove the femoral head. In order to insert a new joint, the damaged bone and cartilage must first be removed.

The hip can be accessed in different ways. Some surgeons get to the hip through the back of the joint (a posterior approach) while others come at the hip through the front of the joint (an anterior approach). This anterior approach is becoming more popular as it seems patients may recover and leave the hospital a little faster after this surgery.

Once the arthritic ball is removed, the worn out socket can be addressed. Unlike the ball, this bone cannot be cut off -- the socket of the hip joint is part of the pelvis bone.

In order to remove the arthritis of the hip socket, a special tool called a reamer is used to scrape away the damaged cartilage and bone. This leaves a smooth, perfectly rounded surface to accept the new hip replacement implant.

Once the damaged bone has been removed from the acetabulum, the new socket of the hip replacement can be inserted. The socket of the pelvis is called the acetabulum, and the part of the hip replacement inserted into the socket is called the acetabular component. Some people also call this component the "cup."

The acetabular component is held tightly in the pelvis by making the socket slightly smaller than the acetabular component, and wedging the implant into the bone. The implant has a rough surface to allow bone to grow into the surface of the implant over time.

Now that the socket has been addressed, attention can turn to the ball of the ball-and-socket hip joint. The ball is supported with an implant inserted down the hollow center of the thigh bone (femur). This implant is called the femoral stem.

Like the acetabular socket, the femoral stem must be held tightly in the bone. Special tools are used to shape the center of the thigh bone to accommodate the femoral stem.

With the bone prepared to accept the stem of the hip replacement implant, the femoral stem is inserted. The stem can be held in the bone with or without cement.

When the bone is held with cement, the cement is inserted in a liquid form, and the stem is then placed. Within a few minutes, the cement permanently hardens to hold the implant fixed within the bone.

When no cement is used, the implant is called "press-fit." This means that the implant is wedged tightly into the bone. A rough surface covering the implant allows bone to grow into the implant over time.

With the stem inserted down the center of the thigh bone, the ball of the ball-and-socket hip joint can be inserted on top of the stem. A metal ball is tightly fit onto the top of the stem. Much of the design of a modern hip replacement implant is really just a way to hold the ball of the hip joint in the right position. There is a style of hip replacement where the ball is resurfaced rather than replaced, meaning there is less implanted material in the body--this style of hip replacement is called hip resurfacing surgery.

With the socket, stem, and ball all inserted, the hip replacement can be placed in final position. With the parts in place, the ball is placed back into the socket -- called reducing the hip.

It is important to ensure the hip replacement implants are stable. Hip replacement implants that are not stable may dislocate, a serious complication of hip replacement surgery.