Hip resurfacing may delay h...

Friday, 3-Aug-2007

In the world of prosthetic hips, what was old is new again. A procedure known as hip resurfacing, once tried two to three decades ago, is experiencing a resurgence in the U.S., thanks to improved technology. The new technique has several advantages over standard total hip replacement (THR) and is an attractive alternative to many people, said Peter Brooks, M.D., a Cleveland Clinic orthopedic surgeon, according to Cleveland Clinic's Men's Health Advisor.

"I think it's probably preferable in the right patient," he said. "They absolutely love it. They love the concept."

However, the procedure isn't for people with weak bones or kidney problems, so it may not be ready to supplant THR as the gold standard in hip prostheses. What's the difference?

In hip resurfacing, a surgeon shaves the head of the femur (the large thigh bone) where it connects to the hip socket (acetabulum). A metallic cap covers the femoral head, guided by a small, short stem drilled into the bone. The capped bone fits into a metallic cup inserted into the acetabulum.

A THR requires the removal of the entire femoral head and neck, replaced with a metallic device with a ceramic or metallic head and a long, thick metal stem that's driven deep into the femur.

The hip resurfacing devices of the 1970s and early 1980s, which used a metallic femoral head and a thin plastic socket, had a high failure rate, and by the mid-1980s, hip resurfacing had largely fallen out of use. A new metal-on-metal resurfacing device has been used in tens of thousands of patients worldwide for more than a decade, but it received U.S. Food and Drug Administration approval only in May 2006. Other devices are awaiting FDA approval.

The advantages

Whereas THR replaces the entire femoral head and neck, resurfacing preserves bone and targets only the problem area: the arthritic surface of the femoral head and acetabulum.

The long stem of a THR alters the natural biomechanics of the hip, resulting in a gradual thinning of the bone at the top of the femur that makes a follow-up THR difficult. Resurfacing preserves the normal hip mechanics and femoral thickness, delays the need for a THR and can easily be converted to a THR should it fail, Dr. Brooks said.

The larger head of the hip resurfacing system makes it more difficult to dislocate, and resurfacing patients generally do not have to follow all the precautions-such as avoiding bending forward more than 90 degrees or crossing their legs-that their THR counterparts must do to prevent dislocation in the weeks after surgery.

Dr. Brooks' patients also have reported that resurfacing feels more natural than a THR.

"I have a number of patients who have a hip replacement on one side and hip resurfacing on the other, and they uniformly prefer the hip resurfacing," he said.

The disadvantages

Despite these pluses, resurfacing has drawbacks. In about 1 to 2 percent of cases, a fracture may develop at the femoral neck, just below where the new metal cap ends. The fractures, which usually occur within four months of surgery, sometimes can be repaired with pins, but a THR may be necessary if the fracture does not heal.

Because of the fracture risk, resurfacing is not recommended for the elderly or people with osteoporosis. Dr. Brooks, who has performed about 60 resurfacings, said the majority of his resurfacing patients are in their 40s and 50s, but some are in their 60s.

Additionally, the resurfacing device can produce potentially toxic metallic ions. Healthy kidneys excrete the metals from the body, but people with impaired kidney function may encounter problems and should not undergo resurfacing.
Finally, the resurfacing operation generally takes more time and is more difficult to perform than THR surgery, and it requires a slightly larger incision. The procedure is relatively new, and only 400 to 500 U.S. surgeons, including Dr. Brooks, are formally trained to perform it.

What to expect

Dr. Brooks' resurfacing patients take a few steps on crutches the day after surgery and usually can go home three days after the procedure. Most patients remain on crutches for six weeks, at which point they return for a check-up, and don't see the doctor again until the one-year mark.

Patients are allowed to do non-impact exercise-walking, biking and swimming-after six weeks, but they must avoid heavy lifting and impact activities such as jogging. After a year, they can do whatever exercise they're fit to handle, he said.

What you can do

• Seek an experienced surgeon, and ask your surgeon how many resurfacings he or she has done.
• Six weeks after your surgery, do only non-impact exercise-such as walking, biking and swimming-and avoid heavy lifting.
• Help maintain bone health by getting at least 1,200 mg of calcium-about two eight-ounce glasses of skim milk-a day if you're over 50, and at least 400-600 international units (IUs) of vitamin D daily, preferably from D-fortified skim milk and fatty fish such as salmon.