Cardiac MRI for Metal on Metal Hip Resurfacing

There has been some recent concern regarding possible systemic health effects resulting from elevated blood cobalt concentrations in patients with cobalt containing hip implants (1). To date there are no blood cobalt criteria to help guide physicians when evaluating an individual hip implant patient's risk of developing systemic health effects because historically there was little or no concern about systemic cobalt toxicity in implant patients. Included within this is heart function, for which investigators see a need to use this novel software to analyze heart function relative to Hip status and Metal Ion levels.

Patients with metal on metal hip prosthesis are subject to local and systemic release of cobalt and chromium ions which may increase the potential for locally aggressive ion-induced local tissue reactions such as pseudotumours, a type of Adverse Reaction to Metal Debris (ARMD) (2). Although there have been reports of local toxicity as well as cases of cobaltism (as seen during outbreak in Quebec of so called 'cobalt beer drinkers' cardiomyopathy) leading to cardiac and ototoxicity, it is unclear if chronic exposure to these ions can lead to impaired cardiac function (cardiotoxicity) in a well-functioning prosthesis.

The majority of the blood cobalt concentrations reported for hip implant patients appear to range from approximately 0.2 to 10 µg/L, and based on our review of the available literature, should not pose an increased risk for the development of systemic health effects.

The concern for systemic health effects is for the small number of patients with cobalt-containing hip implants with markedly elevated blood cobalt concentrations.

Extensive evaluations of these 'cobalt beer drinkers' have found that poor nutrition and underlying disease states caused by severe alcoholism were likely significant contributing factors to heart disease in this particular population. However, there remains a significant concern that cardiac function could be affected in the long term. This is especially relevant as the majority of these implants are put in patients less than 50 years age.

Cardiac magnetic resonance imaging (CMR) is the gold standard method to assess cardiac function in patients at risk of cardiotoxicity. In addition to assessing cardiac function, CMR enables imaging of inflammation, and fibrosis (which may be secondary to the ion deposition) in the heart which may provide more specific information about the mechanism of injury in these patients.

The purpose of this study is to look at cardiac function in patients with a metal on metal hip prostheses.

Recruitment: 30 patients in total (10 unilateral and 10 bilateral hip resurfacing patients and 10 non-metal on metal total hip replacement patients) will be recruited which should provide indication of relationship both between either instances and heart function, as well as compared to one another. All patients will be undergoing clinical cardiac MRI. All patients will have extra images collected during their MRI and these images will be analyzed to determine any relationship between heart function and the possible metal ion levels from the hip implant. As part of the scan analysis they will be required to also have a 5 millilitres (mLs) vial of blood collected. Ultrasound values will be retrospectively collected, for analysis of soft tissue reaction, from a previous clinically ordered ultrasound of the affected joint.

Inclusion criteria

• Undergoing clinical Cardiac MRI
• Currently enrolled with either unilateral or bilateral metal-on-metal (MoM) Hip replacement device
• Willing to sign Informed Consent Form

Exclusion criteria

• Patient does not meet all 'inclusion' criteria