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Spring 2008

Case Study: Metal-on-metal Hip Resurfacing

The patient, a 50-year-old female from Northern California with an arthritic hip, is very active and rows competitively. The pain in her hip, however, is making rowing and even walking difficult. She tried a number of therapies, such as arthroscopy, Hyalgan (sodium hyaluronate) injections and chiropractic care, but nothing helped. She walked with a limp for more than six months before coming to UCSF Medical Center. "I was trying to do everything short of surgery," she says. "But eventually, it became clear that nothing else was going to solve the problem."

Evaluation

After researching both total hip replacement and hip resurfacing, she decided to see Thomas Parker Vail, M.D., chair of the Department of Orthopaedic Surgery at UCSF Medical Center, to learn more about hip resurfacing. One of a handful of orthopaedic surgeons in the country experienced in hip resurfacing, Vail has performed more than 250 resurfacing procedures and has been involved in implant design and clinical trials since 2000. Vail discussed with her the pros and cons of hip resurfacing versus total hip replacement.

Since there is conservation of the bone with hip resurfacing as opposed to total hip replacement, the primary risk is fracture of the bone beneath the metal device. Such risk depends on bone density, in which age is a factor. Vail explained that patients who have strong bones, are active and want to continue to be active are the best candidates for a resurfacing procedure. In Vail's practice, the average age for total hip replacement is 68 and for resurfacing 47.

After a thorough evaluation, the patient showed strong bone density, making her a good candidate for the metal-on-metal hip resurfacing procedure, which she underwent several months later.

Surgical Intervention

At UCSF, the hip resurfacing procedure is done with a modified posterior hip incision that is slightly longer than a modern small posterior total hip incision. Otherwise, the surgical approach to the hip is very similar to that used for total hip replacement, in which the surgeon operates between muscles to access the joint. Preparation of the hip socket is done by shaping the socket with spherical reamers to create a very precise shape into which the new hip resurfacing socket is fitted. The implants generally are available in 2mm increments to fit all sizes of patients.

The socket has a porous surface, so that bone will eventually grow into it, allowing long-term fixation to the pelvis. The femoral head is then prepared by carefully removing small amounts of bone to create a cylindrical shape, onto which a spherical resurfacing cap is placed. This femoral resurfacing cap is fixed into place with bone cement. Both parts of the resurfacing device are made from a highly polished chrome-steel alloy of metal. The hip is then closed anatomically, so that all muscles and attachments are restored.

Outcome and Follow-up

The patient started physical therapy on the day after surgery, and was back to work within two weeks. She remained on crutches for about six weeks due to muscle atrophy that had occurred before the surgery. She received three months of physical therapy, and says now that although her hip is slightly stiff, she no longer has pain and no longer limps. "I'm so much better off than I was before," she says.

Thomas Parker Vail, M.D., can be contacted at (415) 353-2808.

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