Will U.S. Surgeons Heed British Hip Warnings? | Orthopedics This Week
Large Joints and Extremities

Will U.S. Surgeons Heed British Hip Warnings?

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At the British Hip Society's (BHS) annual meeting on March 1, 2012, the Society issued the following statement:

"The BHS advises that stemmed, large diameter metal-on-metal [MoM] primary total hip replacements (THR) using bearings of 36 mm or above should no longer be performed until more evidence is available, except in properly conducted and ethically approved research studies."

In light of such a strong and unusual recommendation, we wondered if their colleagues in the U.S. would follow suit.

We contacted the American Academy of Orthopaedic Surgeons (AAOS) and asked. We also contacted hip manufacturers, the FDA and a respected Wall Street analyst to get their reactions to the call for a ban.

Here's what we found. The AAOS will not recommend a ban; device companies have already adjusted to the dramatic market decline in MoM hips; and the FDA is waiting for safety data required from manufacturers in 2011.

British Data: “High Failure Rates”

The statement from the BHS was followed up by publication of a study on behalf of the National Joint Registry of England and Wales in The Lancet on March 13.

That study found that MoM total hip replacements failed at "high rates." Failure, wrote the authors, was related to head size, with larger heads failing earlier (3.2% cumulative incidence of revision [95% CI 2.5—4.1] for 28 mm and 5.1% [4.2—6.2] for 52 mm head at five years in men aged 60 years).

The authors continued that five-year revision rates in younger women were 6.1% (5.2—7.2) for 46 mm MoM compared with 1.6% (1.3—2.1) for 28 mm metal-on-polyethylene. By contrast, for ceramic-on-ceramic articulations larger head sizes were associated with improved survival (five-year revision rate of 3.3% [2.6—4.1] with 28 mm and 2.0% [1.5—2.7] with 40 mm for men aged 60 years).

The authors concluded: "Metal-on-metal stemmed articulations give poor implant survival compared with other options and should not be implanted. All patients with these bearings should be carefully monitored, particularly young women implanted with large diameter heads. Since large diameter ceramic-on-ceramic bearings seem to do well we support their continued use."

The data was based on more than 400, 000 hip replacements (of which 31, 171 are stemmed MoM) between 2003 and 2011 that were tracked for up to seven years after surgery. Neither hip resurfacing devices, nor data from DePuy's ASR recalled hip device were included in the study. DePuy recently said the company has set aside a multibillion dollar fund to pay for defending litigation and to pay for revision surgeries.

AAOS and Surgeons Respond

Joshua Jacobs, M.D.
Joshua Jacobs, M.D. is the first vice president of AAOS and head of orthopedics at the Rush University Medical Center.

Jacobs told OTW that AAOS has no plans to call for a ban of MoM total hips. He said the Academy serves as an educational resource for its members and will continue to keep members informed of the British recommendations and information from their registry.

He pointed to a recent technology assessment published by the Academy which reported many of the same findings as the registry study. He also pointed to the FDA’s “522” safety data order required of hip device manufacturers in the U.S. Those studies have not been submitted to the FDA. 

"There is a danger in combining all implants into one category, " said Jacobs. He said there are many different categories of implants with an array of different designs. Registry data may miss intra-class differences. Jacobs added that the Academy is very supportive of a registry in the U.S. "We need to know how devices are performing on our population to get a full picture."

"Registry data is helpful in conjunction with other factors, " said Jacobs. "MoM hips are still useful where the device has a good track record and patients have a high risk of dislocation."

Calin Moucha, M.D.
Jacobs said he doesn't use MoM devices and has not used them in the past.

It was a similar story with Mt. Sinai School of Medicine's Associate Chief of Joint Replacement, Calin Moucha, M.D. Moucha was also acting chair of AAOS' Patient Safety Committee in 2011.

Moucha told us that he agrees with Jacobs' assessment, but believes the Academy could play a role in establishing guidelines whereby surgeons can set up protocols to bring back patients with MoM hips and identify problems. He said surgeons need to reassure patients. He told us that he has personally banned MoM hips from his practice.

FDA: Continuing to Monitor and Evaluate

An FDA spokesperson told us the agency was aware of the BHS recommendation but it was important to remember that the majority of MoM hip replacements function effectively. The agency continues to recommend that hip replacement patients undergo regular follow-up with their physicians.

Did the agency fail by allowing MoM hips on the market?

The spokesperson told OTW the agency is evaluating potential relationships of the data reported in the registry to the devices available in the U.S.

MoM total hip devices were cleared through the FDA’s premarket notification (510(k) review process—which required a demonstration of substantial equivalence of the proposed device to predicate devices through preclinical and/or clinical data.

“The regulatory process relies on pre- and post-market evaluation, which balances the innovative technology and its potential benefit to patients with any potential risk.” The spokesperson noted the agency’s request for safety studies after the ASR recall.

“We have asked manufacturers to collect information on MoM THRs…to help us better understand how these devices are performing in the U.S."

“Joint registries in the USA are relatively new, are not representative of all MoM THRs implanted nationally, and do not yet have robust data through five years. Thus, we are also working with the International Consortium of Orthopedic Registries (ICOR) to obtain information in the future regarding both hip and knee replacements." 

“Two projects that have just initiated in ICOR are assessing differences in bearing surface and femoral head size, both of which are covered in the Lancet paper." 

“As part of our post-market evaluation efforts and regulation of these devices, we continue to monitor and evaluate all sources of information for MoM THRs, potential relationships of the MoM THRs reported in this and other registries to MoM THRs and MoM resurfacing hip replacements available in the USA.”

The FDA has provided recommendations to health care providers and patients.

For Health Care Providers:

Patients who present with local symptoms such as pain or decrease in joint function more than three months after MoM total hip replacement surgery should have a thorough evaluation by their orthopedic surgeon.

Patients, including the following, are at risk for increased device wear and/or adverse reactions to metal debris and should be monitored closely:

  • Female patients

  • Patients with small femoral components

  • Patients with increased activity

  • Patients with malpositioned components

  • Patients with bilateral implants

  • Patients with evidence of renal insufficiency

     ♦  Asymptomatic patients should continue to have regular periodic examinations
         with their orthopedic surgeon.  This should include:

          ◊  Careful exam with functional assessment

  • Physical examination of asymptomatic local swelling or masses

  • Careful review of systems for general health changes and evidence of systemic effects

For Patients:

All patients with an implanted MoM total hip system should:

  • Follow their orthopedic surgeon’s recommendations for periodic follow-up examinations

  • Pay close attention to any changes in their general health or if new symptoms outside of their hip develop (i.e., symptoms related to their heart, nervous system, or thyroid gland). Report these symptoms to their primary physician and remind them during the evaluation that they have a MoM total hip implant system, AND

  • Contact their orthopedic surgeon right away if they experience a significant worsening of symptoms or problems three or more months after their MoM total hip system was implanted (i.e., pain, swelling, numbness and/or change in ability to walk)



Device Makers

We contacted six of the largest hip manufacturers to get their responses to the proposed ban. All but Smith & Nephew responded to our request.

Zimmer – “Retired” the Metasul

Zimmer Holdings, Inc. introduced the Metasul MoM bearing in 1988. To date, more than 420, 000 Metasul products have been used worldwide. Zimmer offers MoM bearings in systems with small and large diameter heads (LDH) and in resurfacing (SRA) procedures.

A spokesperson told us the company is aware that there are concerns among surgeons about the potential biologic impact of metal ion release from MoM large diameter heads.

“As a result of this public discussion, demand for MoM articulations has declined substantially over the last several years. Zimmer has therefore decided to retire its Metasul large diameter head products. All other Metasul MoM articulations will remain available, ” said the spokesperson.

Biomet – Surgeon/Patient Decision

A Biomet, Inc. spokesperson told OTW that the company believes that surgeons should choose the appropriate implant in consultation with each patient, based on each patient’s unique condition and expectations.

Stryker – No MoM Device

Globally, Stryker Corporation does not manufacture or distribute a MoM bearing option for total hip arthroplasty.

DePuy – “Ask AAOS”

DePuy Orthopaedics, Inc. referred us to AAOS.

Wright Medical – No Plans to Cease Offering MoM

Wright Medical Technology, Inc. told us that they offer a variety of total implant options, including MoM systems. The company points to the FDA 2011 requirement for post-market surveillance studies for all products that can be used in MoM applications. The company is currently finalizing a clinical plan with FDA to meet the 2011 requirement.

“It is Wright’s common practice to conduct post-market surveillance on all medical devices. We believe our existing data proves the efficacy and safety of Wright’s MoM hip products, and we currently have no plans to cease offering MoM hip systems to surgeons. However, we cannot predict the outcome of industry-wide post-market surveillance, and we reserve the right to modify our products, product offerings, product labeling or directions for use should new information come to light suggesting this is warranted, ” said the company in a statement to OTW.

Wall Street – “Not Much Impact”

Mike Matson
Mizuho Securities USA, Inc.’s Senior Analyst, Mike Matson told OTW that from an investment standpoint he would not expect to see much of an impact to the manufacturers. 

“Utilization of MoM hips has already declined significantly and most of the firms that have sold MoM hips now offer other high-end hips (at similar price levels as MoM) such as ceramic-on-highly cross linked poly as a substitute to MoM in younger patients thereby preserving their revenue and margins.” 

He said companies have not recently disclosed what portion of their hip sales are coming from MoM but thinks exposure is as follows from greatest to least as a portion of overall corporate revenue: Wright Medical, Biomet, Smith & Nephew, Zimmer, Johnson & Johnson (DePuy), and Stryker.

The British Hip Society’s strong warning has clearly reverberated across the Atlantic. But nothing definitive and official appears likely to happen in the U.S. until the FDA gets the safety data required in their 2011 “522” Order. Stay tuned.


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