Total Hip Replacement
When your hip hurts, even everyday tasks, such as rising from a chair or walking, can be difficult. Total hip replacement can relieve this pain and increase motion so you can return to the activities you enjoy.
What Is Hip Replacement?
Hip replacement means removing the damaged ends of bone in the hip joint and replacing them with artificial parts called prostheses. Fig.1 Based on your needs, the surgeon can replace the entire joint or consider hip resurfacing.
How Does the Hip Work?
A joint is an area in the body where the ends of bones meet. In the hip joint, 2 bones meet: the femoral head (ball at the top of the thigh bone) and the acetabulum (rounded socket in the pelvis). Fig.2 Articular cartilage covers the femoral head and the socket. Fig.3 The cartilage cushions and stabilizes the joint and enables the bones to move smoothly against one another. The synovial membrane that lines the rest of the joint produces fluid to lubricate the hip joint. Ligaments connect the bones to each other and stabilize the joint. Fig.4 Tendons connect the surrounding muscles to the bones. The quadriceps (front of thigh) and hamstrings (back of thigh) muscles give the hip strength. Together, these bones and soft tissues enable you to move your leg backward, forward, from side to side, and around.
What Causes Hip Pain and Stiffness?
Disease and injury can damage the articular cartilage, causing it to wear or tear away from the bone. The remaining bare areas of bone rub against each other, resulting in pain and loss of hip function. Arthritis is the most common cause of long-term, disabling hip pain. Other causes include avascular necrosis and non-arthritic trauma.
Osteoarthritis typically affects people who are more than 50 years old and have family members with this disease. Women are at greater risk than men for developing it. Osteoarthritis causes the articular cartilage to wear away slowly. Fig.5
Rheumatoid arthritis can affect people of any age. In this form of arthritis, your body’s immune system attacks the synovial membrane. It becomes inflamed (swollen) and produces too much synovial fluid, which causes the joint to swell. Fig.6 Over time, inflammation damages the articular cartilage.
Traumatic arthritis results from a hip injury that directly or indirectly damages the articular cartilage. Indirect damage can occur over time after you fracture (break) a hip bone or tear a hip ligament. Fig.7
Avascular necrosis most commonly affects men 20 to 40 years old. With this condition, you lose blood supply to part of the bone in the joint. Without a blood supply, the bone develops tiny fractures and, over time, collapses. Fig.8
Non-arthritic trauma describes injury that immediately causes joint pain and loss of motion. For example, fracture of a hip bone or dislocation of the joint can render the hip painful and stiff.
How Will the Surgeon Perform the Hip Replacement?
Typically, the surgeon makes an 8-inch to 10-inch incision to expose the entire joint. He or she removes the femoral head and smoothes the acetabulum. Next, the surgeon shapes the bones to fit the components of the prosthetic joint. The femoral component is a ball on the end of a stem that is made of metal or ceramic. Fig.9A The acetabular component is a cup that is made of metal, plastic, ceramic, or a combination of these materials. Fig.9B The surgeon can secure the components with special cement or through the press-fit method, which relies on bone growing into the components to hold them in place. After ensuring that the components fit properly and that the hip joint functions normally, the surgeon inserts drains to release excess fluid during recovery and closes the incision with staples or stitches. A medical team member applies a sterile bandage to the hip.
Many advances have been made in total hip replacement surgery. For some patients, the surgeon can make a much smaller incision (6 to 8 inches). Fig.10 By using a smaller incision, the surgeon cuts much less tissue, which encourages quicker healing, rehabilitation, and overall recovery.
Hip Differences by Gender
In general, the greatest differences in hip anatomy can be seen when comparing men’s and women’s hips. The head of a typical woman’s hip is not only smaller, but also is angled lower and tends to tilt forward more than a man’s hip. Fig.11
Alternative to Total Hip Replacement
Hip resurfacing is an alternative to total hip replacement for certain active people. The surgeon removes just the damaged areas of the hip joint and replaces the acetabulum with a metal cup and the femoral head with a metal head. Fig.12 A small stem connected to the metal head is inserted into the femoral neck (between the femur and femoral head) and secured with special cement. With resurfacing, less bone is removed, the components may last longer, and the joint functions more normally than with total hip replacement.
Risks and Complications
Hip replacement surgery carries risks and complications:
- Blood clots
- Damage to nerves, blood vessels, and bones around the hip
- Reaction to anesthesia
- Loosening of the artificial parts or joint dislocation
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