New Hip Implants Work No Better than Old Style (MedPage Today)
Newer metal-on-metal or ceramic-on-ceramic hip implants work no better than traditional polyethylene-containing implants, researchers concluded from a systematic review.
Although there are limited comparative effectiveness data, there was no evidence that the newer implant types improved functioning and quality of life or reduced the need for revisions, according to Art Sedrakyan, MD, PhD, of Weill Cornell Medical College in New York City, and colleagues.
“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.
- A study has found that newer metal-on-metal or ceramic-on-ceramic hip implants work no better than traditional polyethylene-containing implants.
- Point out that in the three largest registries, metal-on-metal implants were associated with higher rates of revisions than metal-on-polyethylene implants.
Metal femoral heads with polyethylene cups are traditionally used in hip replacements and are associated with a low risk of revision, which still affects many patients within 10 years due to infection, dislocation, wear, instability, loosening, or other mechanical failures.
Newer metal-on-metal and ceramic-on-ceramic bearings have entered the market in an attempt to reduce the risk of revision even further. But reports of problems involving the accumulation of metal ions in patients’ tissues with metal-on-metal implants have drawn scrutiny from the FDA.
Working with the agency, Sedrakyan and colleagues set out to review the comparative safety and effectiveness of different types of bearing surfaces for hip implants.
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 general, disease-specific functional outcomes and general quality-of-life scores either did not differ between implant types, or showed an advantage for metal-on-polyethylene over metal-on-metal implants in the comparative studies.
In terms of revisions, one comparative study showed fewer dislocations with metal-on-metal implants compared with ceramic-on-polyethylene bearings, and another showed fewer revisions with ceramic-on-ceramic implants versus metal-on-polyethylene bearings.
The data from the national registries did not support those findings, however.
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. Three smaller registries — including one from the Centers for Medicare and Medicaid Services — showed no such difference.
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.
“Changing technology [and] the need to have large numbers of patients, long-term follow-up to establish the safety, and short- and long-term outcomes reported by patients to establish the effectiveness all lead to a lack of strong evidence in orthopedics,” the authors wrote, noting that comparative trials are rare.
The gap in evidence will likely be filled by registries in the near future, they wrote.
“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.
Sedrakyan and colleagues noted some limitations of their review, including reporting quality that was “less than adequate” in the comparative studies, the lack of statistical power in most studies, substantial heterogeneity in the registry evidence, and the possibility of publication bias.