According to a new medical study and analysis, irrespective of the implant material, all types of hip replacement devices appear to work the same. The researchers said, the newer, metal-on-metal implants seem to be no more effective than older implants and may sometimes even be more problematic.
“Metal-on-metal and ceramic-on-ceramic hip implants might not be associated with any advantage, compared with traditional bearings such as metal-on-polyethylene or ceramic-on-polyethylene,” said lead researcher Dr. Art Sedrakyan, director of the Patient-Centered Comparative Effectiveness Program at Weill Cornell Medical College in New York City.
Sedrakyan said there is some medical evidence from three large national registries that higher rates of replacement surgery are associated with metal-on-metal implants, compared with metal-on-polyethylene implants. Even for newer implants such as metal-on-metal or ceramic-on-ceramic bearings, their advantage over traditional implants is not clear, Sedrakyan added.
The report was published in the Nov. 29 online edition of the BMJ.
Older hip implants made with metal-on-polyethylene or ceramic-on-polyethylene surfaces are associated with low failure rates. Newer metal-on-metal hip implants have been linked with severe cases of accumulation of metal ions in patients’ tissues, a condition called metallosis.
Working with the FDA, Sedrakyan’s team looked at the safety and effectiveness of various types of hip implants in 18 studies including more than 3,000 patients and 800,000 operations.
The investigators found no difference between the various types of implants in terms of the patients’ quality of life or ability to function normally. “A large and high-quality randomized controlled trial of bearing surfaces in total hip replacement needs to be conducted before any claims of benefit are made,” they wrote online in BMJ.
The analysis included 3,139 patients (and 3,404 hips) enrolled in 18 randomized trials or comparative observational studies, and more than 830,000 operations in national registries. The mean age of the patients ranged from 42 to 71. Follow-up ranged from three months to 8.1 years.
In the three largest registries — from Australia, New Zealand, and England and Wales — revision rates were higher with metal-on-metal implants compared with metal-on-polyethylene.
Compared with metal-on-polyethylene bearings, ceramic-on-ceramic implants were associated with more revisions in New Zealand, fewer in England and Wales, and a similar number in three other registries. “Only large, longitudinal, multinational registries can provide denominator data for adverse events related to specific implants and allow proper conduct of comparative safety and effectiveness studies, particularly for rare endpoints,” they wrote.
To that end, the FDA has started the International Consortium of Orthopedic Registries to lay the groundwork for a worldwide collection of registries.