Metal Hip Implants Under Review - Analyst Blog


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There is some bad news around for orthopedic devices companies who deal in metal-on-metal ("MoM") hip replacements. A study published recently in The Lancet, the peer-reviewed medical journal, found that failure rates of MoM total hip replacements ("THR") are alarmingly on the higher side.

While THR is a common treatment procedure, it has been observed that some placements fail, especially in younger patients, due to dislocation or material wear. To address these issues, large diameter MoM bearing surfaces were implanted by surgeons. The study's objective was to evaluate if the second alternative led to improved outcome with respect to placements compared with other bearing surfaces. Another aim was to assess if larger head sizes result in improved implant survival.

The study was based on data from the National Joint Registry of England and Wales for primary hip replacements between 2003 and 2011. The findings, however, are not encouraging for players such as Zimmer ( ZMH ), Smith & Nephew ( SNN ) and Johnson & Johnson ( JNJ ) who develop MoM devices.

The failure of MoM THR was found to be more pronounced with larger-head implants and those implanted on women. On the other hand, the outcome was better for ceramic-on-ceramic implants with larger head sizes. These results led the analysts to conclude that MoM devices should not be implanted. Besides, patients with these devices should be monitored properly, particularly young women implanted with large diameter heads.

The latest findings come on the heels of updated advice, in February 2012, from the Medicines and Healthcare products Regulatory Agency ("MHRA") regarding increased scrutiny of patients with MoM implant. The agency has asked the surgeons that patients with MoM hip replacements with head diameters of 36 mm or more should be monitored annually for the life of the hip replacement. This was done to detect any complication at the earliest so that more complex surgeries could be avoided. The previous advice, issued in April 2010, required monitoring for a minimum of five years after the operation.

The US Food and Drug Administration ("FDA") had asked for additional studies on MoM implants from the orthopedic device companies in May 2011.

Concerns about MoM Hip Implants

The FDA noted that MoM replacements have certain specific risks besides the general risks of hip implant systems. Since the metal ball and the metal cup slide against each other during walking or running, some tiny metal particles may wear off of the device and enter into the space around the implant. Moreover, metal ions from the metal implants or from the metal particles may even get into the bloodstream.

Despite several precautions undertaken by orthopedic surgeons to optimize the way in which the ball and socket rub against each other so that fewer wear particles are produced, there is no way to fully avoid the production of metal particles. The reaction to these possible situations is not uniform among the patient population. In some cases, it has been observed that high levels of metal ions in the bloodstream of the patients may adversely affect other parts of the body including the heart, nervous system, and the thyroid gland.

These concerns led DePuy, a unit of Johnson & Johnson, in August 2010 to announce a worldwide voluntary recall of its ASR systems used in hip replacement surgery, principally sold between 2003 and 2009. The recall was based on unpublished data from the UK joint registry which indicated that 13% of the patients who had been implanted the device needed a revision surgery within 5 years. Besides, data from the Australian National Joint Replacement Registry were equally discouraging.


We believe the various post-market studies currently underway should ultimately benefit the huge patient population. However, we also doubt whether an extreme step like an overall ban on the use of this technology is good for patients across the board because these implants could come of help to some patients.

Favorable data from Smith & Nephew on a new study for its Birmingham Hip Resurfacing ("BHR") system announced last month provides a lease of life for this technology. The study, carried out at the request of the FDA, followed the progress of the first 400 BHR patients in the UK. It was observed that after 10 years, 99% were either satisfied or extremely satisfied with their BHR procedure.

Given the mixed reviews, additional and in-depth studies on the use of MoM technology is the call of the hour. The overall risk-benefit profile of this technology ought to be ascertained. Meanwhile, MedTech firms in the replacement niche have to counter yet another looming headwind in an already tight playing field.

We have Neutral recommendations for JNJ, Zimmer, Stryker and Smith & Nephew over the long term.

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The views and opinions expressed herein are the views and opinions of the author and do not necessarily reflect those of Nasdaq, Inc.

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