Hip Replacement: 8% of UK Joints Lack Supporting Evidence

Marcia Frellick

December 20, 2013

Nearly 1 in 12 implants used in hip replacement surgeries in the United Kingdom have no readily available evidence of clinical effectiveness to support their use, according to researchers based at the University of Oxford, United Kingdom.

The results of the study, published online December 19 in the British Medical Journal, come at a time in the United Kingdom when criticism regarding the device regulation system is high and public and professional confidence levels are low. This is particularly true in orthopedics, the authors note, where the failure of many metal-on-metal hip replacements has resulted in a substantial number of revisions.

F. Kynaston-Pearson, from the University Hospitals Birmingham National Health Service Foundation Trust, The Old Queen Elizabeth Hospital, Edgbaston, Birmingham, United Kingdom, and colleagues studied data from the National Joint Registry of England and Wales to identify how many implants used in hip replacement surgeries in 2011 were rated "unclassified" or "preentry" by the Orthopaedic Data Evaluation Panel, the body that rates implants according to levels of evidence.

Unclassified implants have had no evidence submitted by the manufacturers; preentry implants have less than 3 years of evidence.

The authors found that 10,617 (7.8%) of the 136,593 components used in primary hip replacements in 2011 were implanted without readily identifiable evidence of effectiveness. These included 157 cemented stems (0.5% of those implanted), 936 uncemented stems (2.8%), 1732 cemented cups (7.1%), and 7577 uncemented cups (17.1%).

The authors found that 24% (57 of 235) of all hip replacement implants available to surgeons in the United Kingdom have no evidence backing their clinical effectiveness. The way such devices are regulated in the United Kingdom is "entirely inadequate," they conclude.

Among the problems are that medical devices in Europe are evaluated for safety and reliability through any 1 of 76 governing agencies that can allow the device to be marketed in Europe, according to the study authors. In addition, all hip replacement prostheses are considered class 3 devices, which means that an application for approval must include some human clinical investigations but does not have to include "new research specific to the device if the manufacturer is claiming similarity to an existing product."

Loopholes in US System as Well

Although their findings apply to devices implanted in the United Kingdom, the results are useful in other settings, considering most of the prostheses are available in Europe, Australia, and the United States, the authors note.

In the United States, regulation of medical devices falls under a single agency, the US Food and Drug Administration (FDA). However, the FDA's authority to demand rigorous evidence before new devices can be used extends only to high-risk devices, according to an accompanying editorial. Hip reconstruction prostheses are considered moderate-risk and therefore can be cleared through the 510(k) section of the Food, Drug and Cosmetic Act. To be cleared through that program, manufacturers may show that the new product has "substantial equivalence" to a device already on the market. Formal effectiveness trials are rarely done.

"Manufacturers in the US have used the 510(k) pathway to make strings of iterative changes to existing devices, with each new product deemed 'substantially equivalent' to a predecessor, such that hip implants available in 2012 were approved through linkage back to implants produced nearly three decades before," write Aaron Kesselheim, MD, MPH, JD, assistant professor of medicine, and Jerry Avorn, MD, professor of medicine, both from the Program on Regulation, Therapeutics, and Law, Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, in the editorial.

Manufacturers should be restricted in their ability to promote devices or drugs that are authorized by regulators for widespread use but that do not have to pass additional rigorous quality measures, they conclude.

"[P]hysicians who adopt new technologies that have little or no evidence of superiority over existing products need to be educated about the implications of their choices," the editorialists write. "They should also ensure that their patients know about the benefits and risks of the new—but often unproved—medical devices that they are receiving."

This study was supported by the National Institute for Health Research Oxford Musculoskeletal Biomedical Research Unit. One coauthor has received payment for a lecture from Stryker and for education training from Zimmer; 1 coauthor has received consultancy fees from Merck, Roche, Smith and Nephew, Q-Med, Nicox, and Flexion; 1 coauthor has been awarded a grant from Bioberica and Amgen and received a payment for giving a lecture from Bioberica; and 1 coauthor has received grants from Corin and Zimmer. The other authors and the editorialists have disclosed no relevant financial relationships.

BMJ. 2013;347:f7413.


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