Welcome to the website of

Dr. Mark Snyder

"your total joint replacement resource"

Hip Information

TotalHip replacement(THR) is a surgical procedure that replaces the diseased ends of the bones which make up the joint. To accomplish this, surgeons use specially designed implants made from super-alloy metals and/or specifically manufactured Ultra High Molecular Weight Polyethylene. Using precisely engineered surgical instruments, the surgeon will remove the diseased portion and replace it with implants designed strictly for the hip joint.
Over the last quarter century, Ultra High Molecular Weight Polyethylene (UHMWPE) has been preferred for an articulating joint surface. Ultra High Molecular Polyethylene is a plastic material compatible with the human body that provides a low friction bearing surface. Although UHMWPE is an acceptable bearing for many patients, total hip replacements are being performed in younger and more active patients, who challenge the limitations of the standard material. In this decade, the focus of both science and industry has been directed towards defining the factors influencing polyethylene wear and developing new materials for the bearings in hip replacements. Even with the favorable clinical performance of the material, concerns over the possible biologic effect of wear debris have resulted in extensive research into improving this material and developing alternative materials. Today, material developments such as Metal-on-Metal and Ceramic-on-Ceramic are available for consideration for Total Hip Replacement. The following sections will discuss the potential benefits and associated wear rates with these different bearing materials.

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How Hips Work

Your hip is a ball-and-socket joint where the thighbone meets the pelvis. This joint is surrounded by cartilage, muscles and ligaments that allow it to move smoothly. In a healthy hip, smooth cartilage covers the ends of the thighbone as well as the pelvis where it joins the thighbone. This allows the ball to glide easily inside the socket. When the surrounding muscles support your weight and the joint moves smoothly, you can walk painlessly.

Understanding Hip Replacement
In a problem hip, the worn cartilage no longer serves as a cushion. As the roughened bones rub together, they become irregular, with a surface like sandpaper. The ball grinds in the socket when you move your leg, causing pain and stiffness.
With a hip replacement, an artificial ball replaces the head of the thigh bone and an artificial cup replaces the worn socket. A stem is inserted into the thighbone for stability. These parts connect to create your new artificial hip. All parts have smooth surfaces for comfortable movement once you have healed.

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Hip Surgical Procedure

Once you have been prepped for surgery and given an anesthetic, an incision is made down the side of your hip. The ball is cut from the thighbone and the surface of the old socket is smoothed. Then the new socket is put into the pelvis. The socket is usually press-fit and may be held in place with screws or cement. A press fit prosthesis has tiny pores on its surface that your bone will grow into.
Then the new hip stem is inserted into the head of your thighbone. After the stem is secure, the new ball and socket are joined. The stem of the prosthesis may be held with cement or press fit. Your surgeon will choose the method that is best for you.

For more information on these topics, go to the Total Hip Replacement handout that is given to potential hip replacement patients.

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DISCLAIMER
This information is intended for educational purposes only and is not intended to replace advice from your personal physician.