Study Raises Questions About New Joint Implants (MedPageToday)
Innovations to devices used in joint replacement have been introduced without sufficient evidence that they are any better than existing implants, a systematic review suggested.
In fact, for one type of new device technology, hip replacements with modular femoral necks, the cumulative rates of revision surgery at 5 and 10 years were 7.4% and 10.8%, compared with rates of 3.7% and 6.4% for conventional prostheses with nonmodular necks, according to Art Sedrakyan, MD, PhD, of Weill Cornell Medical College in New York City, and colleagues.
That represented a near doubling of the adjusted 10-year revision risk (HR 1.92, 95% CI 1.76-2.10), the researchers reported online in The BMJ.
The publicity surrounding the problems associated with large-size, metal-on-metal hip replacements — high revision rates, recalls, and lawsuits — led to calls from the scientific and regulatory communities for greater oversight of orthopedic implants and other medical devices.
“This systematic review was part of a U.S. Food and Drug Administration-initiated project on comparative effectiveness and safety of orthopedic implants as a reaction to the recent disaster with metal-on-metal articulations,” the researchers wrote.
To see if more caution was indeed being exercised with these devices, Sedrakyan’s group looked at the evidence for “five substantial, innovative, relatively recent, and already widely implemented device technologies used in major total joint replacement.”
They searched the literature for comparative studies on safety and efficacy for modular femoral necks, ceramic-on-ceramic bearings, and uncemented monoblock acetabular cups used in hip replacements, and for gender-specific and high-flexion implants in knee replacements.
They also obtained data from various national registries for long-term outcomes.
For the ceramic-on-ceramic bearings, they identified 42 studies reporting on 23 cohorts. In 13 of the cohorts the comparison was with ceramic-on-polyethylene articulations, and in 10, the comparison was with metal-on-polyethylene bearings.
“None of these studies found a relevant difference in functional and patient-reported outcomes,” the researchers reported.
Audible squeaking was reported in up to 8% of patients with the ceramic-on-ceramic bearings, and not on the other two types. Implant fracture also occurred more often in the ceramic-on-ceramic recipients, but there was less wear over time.
Several national registries reported higher revision rates with the ceramic-on-ceramic bearings. For instance, in the National Joint Registry of England and Wales, the revision rate was 4.3% over 7 years, compared with rates of 3.4% and 3.3% for metal-on-polyethylene and ceramic-on-polyethylene bearings, respectively.
For the uncemented monoblock acetabular cup, three randomized studies showed similar functional and patient-reported outcomes with modular cups at 2 to 4 years, and local bone mineral density was the same with the monoblock versus earlier designs. There were no differences in device survival in these studies.
For the various types of high-flexion knee replacement devices, a “statistically significant but clinically irrelevant increase in postoperative flexion” of 1.6 degrees was seen in randomized studies and 3.7 degrees in nonrandomized studies.
In the Australian joint registry, the 10-year rate for revision with the high-flexion knee device was 5.6% compared with 4.6% for conventional prostheses.
A total of 10 cohorts of gender-specific knee replacements was identified, and in seven of these no differences were found for patient-reported or functional outcomes. A U.S. registry showed similar rates of revision for the gender-specific devices and the unisex devices.
The authors of the report stated that they were not out to criticize the device industry or orthopedic surgeons. “Our goals are to highlight that the status quo regarding the introduction of new device technologies is not acceptable, that substantial efforts are needed by all stakeholders to invest in systems of careful evaluation, and to promote controlled and evidence-based introduction of device innovations,” they wrote.
In an accompanying editorial, Aaron S. Kesselheim, MD, JD, and Prashant V. Rajan, BS, of Harvard University, contended that increased communication with patients is needed so that they can make informed choices.
They noted that “plainly worded drug facts boxes that provide summaries of a product’s supporting evidence” have been tested for pharmaceutical products, and suggested a similar approach for medical devices.
“An equivalent device facts box for hip and knee replacement devices could help correct the overestimation of benefits and underestimation of harms that many consumers would otherwise expect when learning of ‘new and improved’ models,” Kesselheim and Rajan wrote.
They also suggested that registry enrollment should be mandatory.
A limitation of the analysis was that systematic reviews are only as strong as the underlying individual studies, and there was a wide range of quality in those included in the current analysis.