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Questions and Answers about Hip Replacement

What Does Hip Replacement Surgery Involve?

The hip joint is located where the upper end of the femur meets the acetabulum. The femur, or thigh bone, looks like a long stem with a ball on the end. The acetabulum is a socket or cup-like structure in the pelvis, or hip bone. This "ball and socket" arrangement allows a wide range of motion, including sitting, standing, walking, and other daily activities.

During hip replacement, the surgeon removes the diseased bone tissue and cartilage from the hip joint. The healthy parts of the hip are left intact. Then the surgeon replaces the head of the femur (the ball) and the acetabulum (the socket) with new, artificial parts. The new hip is made of materials that allow a natural, gliding motion of the joint. Hip replacement surgery usually lasts 2 to 3 hours.

Sometimes the surgeon will use a special glue, or cement, to bond the new parts of the hip joint to the existing, healthy bone. This is referred to as a "cemented" procedure. In an uncemented procedure, the artificial parts are made of porous material that allows the patient's own bone to grow into the pores and hold the new parts in place. Doctors sometimes use a "hybrid" replacement, which consists of a cemented femur part and an uncemented acetabular part.

Is a Cemented or Uncemented Prosthesis Better?

Cemented prostheses were developed 40 years ago. Uncemented prostheses were developed about 20 years ago to try to avoid the possibility of loosening parts and the breaking off of cement particles, which sometimes happen in the cemented replacement. Because each person's condition is unique, the doctor and patient must weigh the advantages and disadvantages to decide which type of prosthesis is better.

For some people, an uncemented prosthesis may last longer than cemented replacements because there is no cement that can break away. And, if the patient needs an additional hip replacement (which is likely in younger people), also known as a revision, the surgery sometimes is easier if the person has an uncemented prosthesis.

The primary disadvantage of an uncemented prosthesis is the extended recovery period. Because it takes a long time for the natural bone to grow and attach to the prosthesis, people with uncemented replacements must limit activities for up to 3 months to protect the hip joint. The process of natural bone growth also can cause thigh pain for several months after the surgery.

Research has proven the effectiveness of cemented prostheses to reduce pain and increase joint mobility. These results usually are noticeable immediately after surgery. Cemented replacements are more frequently used than cementless ones for older, less active people and people with weak bones, such as those who have osteoporosis.

WebMD Public Information from the U.S. National Institutes of Health

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