BRUSSELS – When younger patients receive a total hip replacement, they are more likely to eventually need revision surgery, compared with older patients, according to findings from a 12-year follow-up study of more than 58,000 Medicare patients.
The finding makes sense and comes as no surprise, but the documentation of a link between younger age and increased revision rates has important implications for prosthesis design.
Dr. Jeffrey N. Katz
“As total hip replacement indications extend to increasingly younger populations, [the patients’] mortality risk will diminish, and a vast majority will remain at risk for revision for decades,” Dr. Jeffrey N. Katz said at the annual World Congress on Osteoarthritis.
“Research evaluating technical innovations to increase prosthesis longevity should recognize the competing risk of mortality. In a 75- or 80-year old, revision is a rather infrequent event; their implant will likely outsurvive them. The older a patient is, the more likely the patient is to die with their original prosthesis intact,” said Dr. Katz of the department of medicine at Harvard Medical School, Boston, and director of the orthopedic and arthritis center for outcomes research at Brigham and Women’s Hospital in that city.
“If a prosthesis manufacturer wants to increase the longevity of a prosthesis, the patients to target are those younger than 65. For patients who gets through the perioperative period, the real issue is biomaterials: How likely are the biomaterials to wear out over time?” he noted.
Currently, about 280,000 total hip replacements are performed in the United States annually (more than 90% because of osteoarthritis), along with 40,000 revision hip surgeries each year. Revisions alone cost more than $1 billion annually.
Dr. Katz and his associates studied the 58,521 Medicare beneficiaries who underwent a total hip replacement during July 1995–June 1996. Two-thirds were women, and 60% were aged 65-75 years, with the remaining patients older than 75 years. The researchers had complete follow-up records for all patients for the subsequent 12 years, through 2008. They presumed that all patients in this group with subsequent hip surgery had revisions, although it’s also possible that the second surgery involved the contralateral hip.
During follow-up, 60% of the patients who were older than 75 years at the time of surgery died; during the 12-year follow-up, the survivors had a revision rate of 9%. Among patients aged 65-75 years at the time of their initial hip surgery, 30% died during follow-up, with the survivors having a 13% revision rate. In both age groups, men had a higher revision rate than did women.
“Younger patients are more active and heavier,” Dr. Katz explained in an interview at the congress, which was organized by the Osteoarthritis Research Society International. “Younger patients probably wear their [prosthetic] joints out faster, and – given the same amount of wear – they are offered [revision] surgery more frequently and they accept surgery more frequently.
“We don’t have data for 45- to 65-year-olds, but by extension, their mortality is unlikely over the following 20 years, while a revision is likely. The younger age group has a very real risk of facing a revision in their lifetime. If a manufacturer could improve the longevity of their prosthesis, it would potentially save them an operation,” Dr. Katz said.
Dr. Katz said that he had no disclosures.