Features January 2013 Issue

Your Arthritic Hip: Resurface or Replace?

Hip resurfacing is an alternative to total hip replacement, but it’s not without risks and it’s not for everyone.

Total hip replacement (THR) is one of the success stories of orthopaedic surgery. For older adults with hip joints eroded by osteoarthritis, this proven operation can ease pain and improve function.

Hip resurfacing uses a metal cap (A) that fits over the top of the femur and a cup that fits in the pelvic socket. It requires minimal bone removal. Hip replacement involves removing the top of the femur and a portion of the pelvic socket, then implanting a prosthetic hip implant (B) in the femur and a new socket in the pelvis.

For younger, more active patients, a procedure known as hip resurfacing may be a more attractive alternative. Some evidence suggests that resurfacing affords patients a higher level of activity after surgery, without some of the post-operative precautions and limitations often placed on THR patients.

But like all operations, hip resurfacing has risks. And, the number of true candidates for resurfacing is relatively small.

“If you pick the right patient, you have a properly designed device, and the operation is done right, you should be fine,” says Peter Brooks, MD, a Cleveland Clinic orthopaedic surgeon who specializes in hip resurfacing.

Resurfacing vs. replaceme
ntIn THR, a surgeon replaces the head of the thigh bone, or femur, with a metal or hard ceramic ball attached to a metal stem driven into the femoral shaft. The hip socket, or acetabulum, is replaced with a durable plastic, ceramic, or metal cup. With hip resurfacing, the femoral head is left intact but is shaved and covered with a metal cap attached to a short stem drilled into the bone. The cap bears against a metal acetabular cup.

The larger head of the resurfacing implant makes it less likely to dislocate than a THR, Dr. Brooks says. So, resurfacing patients generally do not have to follow the precautions that their THR counterparts must do in the weeks after surgery, such as avoiding bending forward more than 90 degrees.

Many surgeons advise THR patients against heavy lifting or high-impact running or jumping on their new hips. After spending a year recovering and allowing the hip bones to strengthen, hip resurfacing patients face no such limitations, Dr. Brooks says.

Also, hip resurfacing preserves more bone than THR, which removes the entire femoral head and neck. This bone-sparing nature allows for a relatively easy conversion of a hip resurfacing to a THR should the initial implant fail, whereas revision surgery to correct a failed initial THR is more complicated, Dr. Brooks says.

“I tell patients that you don’t have to worry about your first total hip replacement,” he adds. “But you should be concerned about the revision. You go on losing bone when you take the old one out and put the new one in. At least with resurfacing, you’re one stage removed from that.”

The downside
Hip resurfacing isn’t without risks, however. In about 1 to 2 percent of cases, a fracture develops at the femoral neck, usually within four months of surgery. As a precaution, resurfacing patients often wait a few weeks longer than THR patients to put full weight on their repaired hip. Dr. Brooks notes that only one of his more than 1,400 resurfacing patients has experienced a femoral neck fracture.

Given the fracture risk, resurfacing is not recommended for the elderly or those with osteoporosis or severe avascular necrosis, a bone-decaying condition. Likewise, people with severe hip dysplasia also should not undergo hip resurfacing, Dr. Brooks advises.

Another potential drawback is that metal-on-metal bearing surfaces can produce potentially toxic metallic ions. Healthy kidneys clear these metals from the body, but people with kidney disease may have problems and should not undergo resurfacing. These ions also can cause adverse reactions that erode bone and loosen the implant, prompting the recall of some metal-on-metal THR implants; however, Dr. Brooks says the amount of metal produced by a resurfacing implant is significantly less, “and we have plenty of evidence that it’s perfectly safe.”

Are you a candidate?
The success of hip resurfacing may depend on the size of the individual and implant. Since men typically have larger bones than women, they generally can be treated with a larger femoral component, which adds stability to the joint. A study published online Oct. 2, 2012, in The Lancet found that only men fitted with larger resurfacing femoral heads had five-year implant survival rates comparable to those of THR. For all women, as well as men with smaller femoral heads, the five-year implant survival rate was lower with hip resurfacing than with THR, the researchers reported.

Thus, resurfacing is best suited for younger, larger-framed men who are more active and healthy enough to benefit from the operation, Dr. Brooks says.

“We tend to do more resurfacing in men and more total hip replacement in women,” he says, adding that only about 7 percent of all hip arthroplasty surgeries are resurfacings. “I steer patients towards total hip replacement if they’re smaller because there’s good evidence that the bigger your bones are, the better candidate you are for resurfacing.”

Whether you opt for hip resurfacing or THR, Dr. Brooks says, choose a surgeon who has done either procedure at least 100 times and performs each one routinely.

“Get an opinion from someone who does both resurfacing and total hip replacement,” Dr. Brooks says. “If you think you might be a candidate for resurfacing and you go to someone who does both procedures, you can believe it if he or she says you’re not a candidate for resurfacing.”