Your Hip and How it Works
When a hip becomes diseased or injured, simple movements can be painful and take the joy out of life. Most people want relief from the pain and disability caused by severe arthritis. Your reasons for having surgery are very personal. Only you can finish this sentence: "If I didn't have pain I would . . ." You and your doctor have decided that total hip replacement surgery may help relieve much of your pain.
The main benefit you may expect from total hip replacement is pain relief, which can be quite dramatic. Most patients will notice some soreness for several weeks or months after surgery. In most cases, however, pain-free motion of the hip joint will follow.
The "Normal" Hip
A joint is a special structure in the body where the ends of two or more bones meet. The hip is a "ball-and-socket" joint. The upper end of the thighbone (femur) is the ball. It fits into the socket (acetabulum) in the pelvis. The joint lining (synovium) makes fluid that lubricates the joint. Cartilage covers the ends of the bones. This cartilage "cushions" the hip joint for smooth, easy movement. The hip, your body's largest weight bearing joint, is held together by muscles and ligaments that allow your leg to move so you can walk and climb stairs.
The "Problem" Hip
When a hip is diseased, such as with arthritis, the cartilage wears away. The bones become rough and grind together, causing pain.
There are many different types of arthritis. One major type is osteoarthritis, which is also called degenerative joint disease, or the "aging arthritis." Another form, rheumatoid arthritis, is a chronic disease that affects many parts of the body. There can also be joint destruction due to loss of blood supply (osteonecrosis) or from injuries (traumatic arthritis). After you condition has been diagnosed, and if other medical treatments have failed to help you, the orthopedic surgeon can replace your diseased joint and soon relieve your pain. Total hip replacement is not done for minor arthritis pain.
Your New Hip
Total hip replacement surgery involves removing the diseased portion of the hip joint. An artificial hip, known as a prosthesis, replaces it. A cup replaces the worn hip socket and a ball on a stem that is inserted into the thighbone replaces the worn head of the thighbone (femur). These parts are most commonly made up of metal, plastic or ceramic and come in various sizes and designs.
There are two methods of securing the new prosthesis in place. One method uses bone cement and is called the "cemented" method. The other type is secured in place by the body's own bone growth and is called the "cementless" or "ingrowth" method. Your surgeon will help you decide which is best for you and will discuss this with you before surgery. There are times, however, when the decision can be made only at the time of your operation.
The "Cemented" Hip
The cement used to hold the cup and stem in place does not work like glue. Instead, it works by filling in the spaces between the bone and the surface of the prosthesis. After a few minutes the cement hardens and fixes the prosthesis to the bone. Most patients can immediately bear full weight regardless of fixation type.
The "Ingrowth" Hip
An ingrowth hip uses no cement, so the new prosthesis needs to fit very tightly in the bone. The patient's bone will eventually grow into a porous surface on the prosthesis. Because this requires good healthy bone, not every patient is a suitable candidate for this type of hip.
The ingrowth prosthesis may be held in place with screws to aid in fixation until the bone grows into the cup. Because it takes time for the bone to grow into the prosthesis, your hip may need more protection at first. It may be necessary for you to use crutches or a walker for two or more months. Your therapists and surgeon will decide when it is safe for you to stop using your crutches or walker.
Bearing Surfaces
The bearing surface of a hip replacement is where the ball makes contact with the socket. This surface can be made of plastic (polyethylene) metal, or a ceramic material. The advantages and disadvantages of each type may be discussed with your surgeon.
Incision
Our surgeons have performed many small incision hip replacements with incisions which allow adequate visualization of the hip to place the implants in their proper position. The length of the incision depends on the size of the patient, the pre-operative hip deformity, and the ability to adequately see the hip. Newer instruments and techniques have helped decrease the length of the incision and encourage muscle and soft tissue healing after hip replacement surgery.