NEW YORK, NY – A bone-sparing, hip-resurfacing system recently approved by the US Food and Drug Administration and now being used in a handful of US hospitals will likely relieve pain and improve hip function among younger, active patients with good bone quality, but it may not be appropriate for older patients with more fragile bones, orthopaedic surgeons told CIAOMed.
The Birmingham system has been used worldwide since 1997 and has two parts: a socket in the shape of a shallow cup (acetabular component), and a cap in the form of a ball head (femoral resurfacing component). The cup replaces the damaged surface of the acetabulum, while the cap covers the ball-shaped bone at the top of the femoral head. The cap has a small stem that is inserted into the top of the thighbone. The cap moves within the cup.
William B. Macaulay, MD, director of the Center for Hip and Knee Replacements at New York Presbyterian Hospital/Columbia University in New York City, predicted that the hip resurfacing system might take over 20%–30% of the hip replacement market in the US over the next 20 years. "It will conserve bone, and if a patient ever needed to have it revised, it is more like doing a primary hip replacement than a true revision," said Dr. Macaulay, who has done about 50 resurfacing procedures and plans to teach the procedure to other surgeons in the future.
"The ideal candidate is somebody who is extremely active, has very severe hip arthritis, is on the younger side, and has strong bone and doesn't want to wait until they are older to have a hip replacement," Dr. Macaulay said. The "maximally bone-conserving" procedure is successful at relieving pain; it's not a temporizing thing, he noted. "There is a chance that it may need to be revised, but it could be the one and only procedure a patient ever has."
The durability of the resurfaced hip is unknown, but in one study the device survival rate was 98.4% at 5 years, which is comparable to that of traditional total hip replacement in patients under age 60.
"The ideal patient for this procedure is under 55 years of age, and this has to do with the physiologic age of bone," concurred James Kudrna, MD, PhD, of Northwestern University Medical School in Chicago, Illinois, and Evanston Northwestern Healthcare in Evanston, Illinois.
"The main benefit of this device is that when the surgical procedure is performed, a greater amount of bone is conserved," Dr. Kudrna told CIAOMed. "In total hip replacement, the entire ball of the femur is excised, but in resurfacing, it's just cleaned off and we mount a metal cap."
As a result, the mobility and stability of the hip are improved. "The risk of dislocation is extremely rare, and osteolysis is not a major issue with this particular type of device," Dr. Kudrna said. Metal-on-metal implants avoid the polyethylene wear problems that can lead to premature loosening of the hip replacement implant.
Caveats concerning age, gender
This procedure is not for every patient, Dr. Macaulay cautioned. "This is not the right operation for a 72-year-old, tall, thin, Caucasian patient with risk factors for osteoporosis, even if they are extremely active, because of their poor bone quality and increased risk for femoral neck fracture," he said.
Women are more likely to sustain femoral neck fracture in their 60s, 70s, and 80s, and Dr. Macaulay said that the female patient "needs to be aware that if she is in that age group or going to be there someday, resurfacing may increase her chances of needing to have [a total hip replacement]."
Resurfacing also is not a good choice for patients with severe kidney impairment. "The metal-on-metal device creates ions and small metallic debris in the bloodstream, and the body normally clears these easily unless a patient has renal impairment," Dr. Macaulay explained.
He also warned that there will be a fairly steep learning curve among surgeons. "The community orthopaedic surgeon who does 5–10 hip replacements per year is not the right person to perform this procedure," he said.
PubMed: Related Articles