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The case of metal-on-metal implant recalls: what have we learned?

G. Manoudis, J. Antoniou

In recent decades, the introduction of new drugs and implants has often been accompanied by enthusiastic acceptance by the medical community. However there are cases where this initial enthusiasm is dampened by unexpected complications.

A typical example of this is the case of silicone breast implants that were manufactured in the early 1960s by Dow Corning (Midland, Michigan) and were successfully used by plastic surgeons for several years. Throughout the 1980s and 1990s reports began to arise, claiming that the silicone breast implants were causing systemic health problems. These led to numerous lawsuits beginning in 1984, culminating in a 1998 multi-billion dollar class action settlement. As a result, Dow Corning was in bankruptcy protection for nine years, ending in June 2004. A number of large, independent reviews of the scientific literature, including the United States Institute of Medicine, have since found that silicone breast implants do not appear to cause breast cancers or any identifiable systemic disease. Silicone is, once again, routinely found in breast implants.

In orthopaedic surgery, there are several examples of recalled implants. In 2008, Stryker (Kalamazoo, Michigan) voluntarily recalled the Trident PSL Acetabular and Hemispherical Acetabular Cup because of poor fixation, squeaking and improper seating due to broach mismatch that resulted in fractures. On the other hand, many implants have been discontinued because of poor performance, but were never actually recalled.

Sulzer Medica issued a voluntary recall of its Inter-Op metal-on-metal (MoM) shell in January 2001, after a series of adverse reports from surgeons1 led to the discovery that a lubricant had leaked into the manufacturing device coolant and contaminated approximately 25 000 units, of which 17 500 were implanted. The lubricant was a mineral oil-based substance that remained as residue and prevented bone ingrowth, resulting in loosening of the implant. In our department, of the 163 Inter-op prostheses implanted, 11 were revised because of the manufacturer’s recall at a mean of 1.1 years. The overall survivorship rate for all-cause revision was 91.3%, with this rate increasing to 97.5% at nine years when excluding the recalled hips.

The Articular Surface Replacement (ASR) hip resurfacing and MoM arthroplasty (DePuy Orthopaedics, Warsaw, Indiana) system were introduced in early 2004. In September 2010, DePuy recalled the ASR hip implants. Data from the national joint registries of England and Wales and Australia found that the ASR Resurfacing System had a revision rate of 12% and the ASR XL Acetabular System had a revision rate of 13%. Reasons for failure include loosening, fracture, dislocation and rarely a localised soft-tissue reaction called ‘pseudotumour’. Jameson et al2 reported on 214 ASR resurfacings, of which 40% were in women, with a mean follow-up of 43 months. There were 12 revisions (5.6%) and the overall survival was 93% (89% for hips with acetabular components < 56 mm in diameter). Lower diametrical clearance and the subhemispherical acetabular component may have contributed to the higher failure rate when compared to other designs. Langton et al3 reported a 25% failure rate at six years of the ASR resurfacing and a 49% failure of the ASR THR. They concluded that the design of the ASR acetabular component and its predisposition to edge wear are likely to be the most important contributors to failure. They also reported that abnormal wear at the head–neck junction may be a major contributing factor to the development of pseudotumour in MoM hip replacements using bearing diameters ≥ 36 mm.

In our department, 594 ASR resurfacings were implanted over 80 months with a mean follow-up of five years. Overall, we had 16 failures (2.7%), five femoral neck fractures, two acetabular component loosening, two femoral component loosening, two avascular necrosis of the femoral head and three infections. Two cases were revised since the recall was announced. One for fear of having a recalled implant and one because of high ion levels, both in well-functioning prostheses. The survivorship rate is 97.3% at 7.5 years. We have undertaken no revisions for pseudotumours. Given the wide discrepancy in clinical outcomes with the same implant, there seems to also be technique and patient selection variables at play.

On April 2010, the British Orthopaedic Association (BOA) issued a medical device alert for all MoM hip replacements with specific recommendations for follow-up, testing and metal ion levels, without highlighting a particular device. In February 2011, the Canadian Orthopaedic Association (COA) issued similar recommendations but pinpointed ASR specifically. DePuy sent a letter, prepared by lawyers, to all patients, which included recommendations for evaluation and treatment. However, many of these recommendations are not based on solid scientific data. We issued a letter to all of our patients explaining the situation and discussing our outcomes. We reassured our patients that in the absence of pain or symptoms, the serious soft-tissue reactions are rare. We closely follow our patients annually, evaluating them clinically, radiologically and by measuring cobalt and chromium ion levels. In the presence of symptoms or high ion levels, an MRI using metal artifact reduction sequence (MARS)4 is routinely performed.

‘Recall’ is an unfortunate word to use for any implanted material and some have argued that the word should be changed to ‘medical advisory’. It is essential to closely follow patients, answer all their questions and calm their anxiety. Use of the term recall leads to an expanding wave of hysteria, fanned by lawyers and the Internet, that can lead to unnecessary or even risky actions. In many cases, the true reasons for failures  are multifactorial, including improper patient selection, surgical technique and implant design. As we are currently dealing with incomplete data in a very volatile environment, it is imperative that cooler heads prevail and that a panel of experts be consulted anytime an official position is taken by any association. All recommendations should include the level of evidence on which they are based. Our goal should be to minimise needless fear while keeping both surgeons and patients informed.

Key summary points

1. The use of the term “recall” when it comes to implants is controversial. The medical community may be better served by terms such as “medical advisory”.

2. Given the mounting hysteria surrounding a recall, communicating and informing all affected patients is very helpful in mitigating undue stress.

3. Professional associations should communicate official recommendations based on the informed opinion of an expert panel. The level of evidence behind the recommendations should also be cited.

 

This article was originally published in the Canadian Orthopaedic Association’s COA Bulletin #95, Winter 2011 edition.

 

References

1. Blumenfeld TJ, Bargar WL. Early aseptic loosening of a modern acetabular component secondary to a change in manufacturing. J Arthroplasty 2006;21:689-95.

2. Jameson SS, Langton DJ, Nargol AV. Articular surface replacement of the hip: a prospective single-surgeon series. J Bone Joint Surg [Br] 2010;92-B:28-37.

3. Langton DJ, Jameson SS, Joyce TJ, et al. Accelerating failure rate of the ASR total hip replacement. J Bone Joint Surg [Br] 2011;93-B:1011-16.

4. Mistry A, Cahir J, Donell ST, Nolan J, Toms AP. MRI of asymptomatic patients with metal-on-metal and polyethylene-on-metal total hip arthroplasties. Clin Radiol 2011;66:540-5.