The Evidence for the Safety and Efficacy of Metal-On-Metal Hip Prostheses

Essay, 2017

12 Pages, Grade: 1





Materials and Design

Clinical Safety and Efficacy





Metal-on-metal prostheses have been in use since 1960’s, and their safety and efficacy has never been reviewed adequately. The current reports of metal-on-metal hip implants’ failure have led to health concerns

Materials and Design

Materials used in the analysis were the Cormet Hip Resurfacing System and Birmingham Hip Resurfacing System. Literature materials were analyzed using the Cox regression model.

Critical Safety and Efficacy

Literature sources indicate that, the failures observed in the two metal-on-metal hip devices can be attributed to the lack of efficient regulatory policies. Epidemiological reports indicate that most patients around the globe have experienced the adverse effects of metal-on-metal hip implants.

It is argued that, FDA failed to carry out comprehensive evaluation on the safety and efficacy of metal-on-metal hip devices before their approval to reduce the health risks associated to the devices.

Evidence to the insufficiency of the evidence provided by the regulatory agencies can be provided by the confession of the duPuy’s designer. Recently, he admitted that the devices should not be in use today because they encompass enormous defaults.


The procedure of technology assessment has been found to have been based on inappropriate scientific evidence. Cormet 2000 and the BHR devices’ technology assessment did not meet all the required criteria. Therefore, evidence for the safety and efficacy of metal-on-metal hip prostheses in 2005 was insufficient.


Metal-on-metal hip prostheses have been in use clinical since 1960s, and its literature review has been showing diverse changes. Clinical studies have been conducted to ascertain the usefulness of the technology in regard to its safety and efficacy (Amstutz & LeDuff 2006). Ordinarily, metal-on-metal total hip implants are believed to release toxic substances in the patient’s body, causing significant health concerns of the technology. Cohen (2012, par. 1) reaffirms “thousands of patients around the world may have been exposed to toxic substances after being implanted with poorly regulated and potentially dangerous hip devices.” Therefore, this paper will provide a critical review on the evidence for the safety and efficacy of metal-on-metal hip prostheses, primarily with regard to its insufficiency.

Materials and Design

Analysis of the literature involved the use of different literature sources, which were analyzed using the Cox regression model.

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Figure 1: Trabecular Metal™ Primary Hip Prosthesis

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Figure 2: Cormet 2000 device on the femoral cup (Allan et al. 2009)

Device Composition

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Clinical Safety and Efficacy

Literature materials indicate that, FDA has not been able to design efficient regulatory measures aimed at reducing the risk posed by metal-on-metal hip arthroplasty. For instance, reports indicate that FDA was aware of the safety and efficacy issues related to metal-on-metal hip arthroplasty, but it maintained that there was a need for scientific data to unravel the mystery surrounding the technology. Surprisingly, FDA seems to have neglected the issue and continued to allow clearance of metal-on-metal hip implants for marketing. It is argued that FDA carries the blame for the damage incurred over the last thirty years for failing in its primary mission. In this case, the agency did not apply ethical standards in allowing clearance for metal-on-metal hip implants. It is argued that they were “fully aware of the deadly risks in use of toxic metal device failures for these implants, but the agency failed in its primary mission and continued to allow massive proliferation with full FDA clearance for marketing, unfettered by oversight” (Schrag 2013, p. 2).

Recently, Thomas P. Schmalzried astonished the public and healthcare professionals by testifying in the Chicago’s court case that he “had to revise 15 out of 66 insertions (23 percent failure rate), which he said, is an unacceptable failure rate” (Schrag 2013, p. 3). Ironically, FDA provided full market clearance for metal-on-metal hip implants in 2005, leading to the release of over 34,000 metal-on-metal devices in the United States. Schrag (2013, p. 3) reports “in a separate news report dated April 2, 2013, Dr. Schmalzried further testified that he would not use ASR and that its benefits do not outweigh the risk.” This testimony provides evidence to the safety and efficacy concerns on the metal-on-metal hip implants, but FDA seems to have neglected the risks associated with the implants for total hip replacement (Duncan et al. 2010).

Ideally, FDA based its evidence on the benefits of metal-on-metal hip implants for total hip replacement. Currently, metal-on-metal hip implants are used as a reliable alternative for total hip replacement (Bruening et al. 2006). Despite the failure rates observed by surgeons in 1980s, total hip replacement prostheses gained popularity in 1990s because of their usefulness in treating young and active patients (Dettori et al. 2013).

From a clinical perspective, the use of total hip replacement, primarily metal-on-metal hip devices has several advantages compared to the hip resurfacing (Bozic et al. 2010). For instance, it has been reported that metal-on-metal hip implants “provide the ability to use large diameter femoral head sizes compared to other articulating combinations” (Dettori et al. p. 21). In addition, metal-on-metal hip implants have large sizes, which are believed to mimic the patient’s natural anatomy. Therefore, they reduce post-operative dislocation through the improvement of the joint stability (Lee, McIsaac & Noseworthy 2007).

Despite the benefits associated with metal-on-metal hip implants, they encompass enormous safety concerns because they produce metal ions such as Chromium and Cobalt, which cause peri-prosthetic tissue and bone destruction (Brazzelli et al. 2004). Therefore, evidence for the safety and efficacy of metal-on-metal hip prostheses released in 2005 appears to be insufficient in various perspectives.

Insufficiency of the evidence for the safety and efficacy of metal-on-metal hip prostheses can be explained by highlighting on the safety concerns associated with the procedures. It is suggested that FDA should have followed Technology Assessment guidelines before the approval of metal-on-metal hip implants for commercial production. In addition, it should have evaluated the devices design, uncertain risks from metal ions and post-marketing surveillance to reduce its safety risks on patients.

It is argued that regulators in the United States and Europe did not identify the tweaked designs by manufacturers of metal-on-metal hip implants before granting them approval, and yet the designers were aware of the dangers. These design changes are believed to have encompassed enormous consequences on the patients’ safety. Cohen (2012, par. 27) reports “instead of alerting regulators and patients to their concerns, companies tweaked the design of their total hip implants.” One surgeon who had been using metal-on-metal hip implants was quoted saying, “We are seeing patients with tapers which are blackened, destroyed, metal getting into the tissues of the hip, damaging the muscles, taking out some of the bone, so destroying parts of the pelvis” (Cohen 2012, par. 32). Research studies indicate that, Cobalt and Chromium ions are carcinogenic because they were found to cause genotoxic changes in animals (Dayan & Paine 2001). However, regulatory agencies in the United Kingdom noticed that fact recently after the London Implant Retrieval Centre confirmed the release of trivalent Chromium ions by the metal-on-metal hip implants (Ladon et al 2004). Therefore, the high failure rate of metal-on-metal hip implants was attributable to the release of the genotoxic metal ions during the post-operative period (Amstutz, Ball & LeDuff 2007).

According to dePuy’s designer Dr. Schmalzried, Cobalt release by the device is relatively low, primarily in patients whose devices function well. He states that patients with well-functioning metal-to-metal hip implants do not record his level of Cobalt ions in their blood circulations (Antoniou et al. 2008). However, “studies show that blood Cobalt concentrations generated through the wear of some of the newer metal-on-metal total hip prostheses can reach over 300μg/L, higher than anything routinely documented in the past” (Cohen 2012, par. 21). Surprisingly, regulatory agencies in Europe and the U.S failed to identify the genotoxic aspect of the metal-on-metal hip implants before approval in 2005, leading the current health consequences.

On the other hand, the criteria used in assessing the safety and efficacy of metal-on-metal hip prostheses in 2005 were not sufficient. It has been found that, the approved prostheses met only one of the five criteria used in determining the safety and efficacy of new technologies applied in for hip arthroplasty.

According to the California Technology Assessment Forum, the Birmingham Hip Resurfacing (BHR) and Cormet 2000 devices met the first technology assessment criterion, which requires government regulatory bodies to approve new technologies used for prosthetic purposes before allowing manufacturers to produce them for marketing. On 9 May, 2006, the Birmingham Hip Resurfacing System received FDA’s pre-market approval although there were several conditions (Back et al. 2005). Some of these conditions included the implementation of a training program to provide a comprehensive analysis of the adverse effects. In addition, a learning curve was to be evaluated to determine the safety and efficacy of the technology (Karliner 2010).

On the other hand, the Cormet Hip Resurfacing (Cormet 2000) System was approved on 3 July, 2007 after a comprehensive review of two post-approval studies. In addition to the two post-approval studies, FDA required the Cormet 2000 producer and other healthcare stakeholders to establish strategies for performance assessment, primarily under the appropriate conditions (CTAF 2007).


Excerpt out of 12 pages


The Evidence for the Safety and Efficacy of Metal-On-Metal Hip Prostheses
Egerton University
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ISBN (Book)
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evidence, safety, efficacy, metal-on-metal, prostheses
Quote paper
Patrick Kimuyu (Author), 2017, The Evidence for the Safety and Efficacy of Metal-On-Metal Hip Prostheses, Munich, GRIN Verlag,


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