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Hip Replacement & metallosis: A growing concern?

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    Abigail Ringer considers metallosis, a potential complication of hip replacement surgery, and the potential toxic effects of tiny metal particles released from hip replacement joints, and how this condition may give rise to a clinical negligence claim.

    By Abigail Ringer

Last year, according to the National Joint Registry, nearly one hundred thousand hip operations were undertaken in the UK; an ever increasing number to keep up with our aging population. Yet little seems to be known about metallosis, a potential complication of hip replacement surgery that can have widespread consequences in the human body.

What is metallosis?

Metallosis describes the build up of tiny metal particles in the body which, following hip replacement surgery, come from the wearing down of the metal in the artificial joint.

If we imagine a hip joint, the artificial joint (just like the natural joint it endeavours to replicate), is made up of a ball which fits in to a socket. Some artificial joints are made from a metal ball within a metal socket and these are referred to as ‘metal-on-metal joints’. Others have a layer of plastic which overlays the metal socket and these are referred to as ‘metal-on-plastic joints’. As the surface of the metal endures mechanical wear and corrosion, tiny particles of metal break off and circulate around the body [1]. These metal particles lead to the formation of swelling and scarring around the joint and can result in the prosthetic joint becoming loose.

What are the symptoms and effects of metallosis?

The symptoms of metallosis are reported to include pain and swelling around the hip joint that was not there immediately after surgery. Sometimes people experience clicking sounds from the hip. Metallosis is normally confirmed by a laboratory test to measure the amount of metal particles in both the fluid around the joint and in the blood.

Whilst the local affects of metallosis around the affected hip have been appreciated for a number of years, it is only more recently that scientists and doctors are beginning to recognise the potential effects that these tiny metal particles may have on the rest of the body.  By way of example, increased levels of metal in the blood have been documented to:

  • interfere with the way in which the body fights infection [2];
  • cause damage to heart muscle [3];
  • result in bone pain [4].

I have also read about a case of a man with extremely high levels of metal in his body damaging his eyesight and hearing [5].

How is metallosis treated?

The only available treatment for metallosis involves surgery to resurface or revise the hip and according to one study [6], almost all patients respond favourably to surgery.

Metallosis and clinical negligence cases

I and my colleagues act for a number of patients with cases relating to negligence surrounding hip replacement surgery, and these include clients who have been diagnosed with metallosis and associated complications.  As the potential wide-ranging effects of metallosis are better understood I wonder if the number of cases involving metallosis will start to increase.  For example, if a patient with a known history of hip replacement surgery with metal implants subsequently presents with symptoms potentially being caused by metallosis and there is a delay in investigating if this is the cause of their symptoms and, if confirmed, carrying our further surgery, and as a result the patient suffers further injury from the metallosis then this may give rise to a negligence claim.

[1] Keegan, G. et al. Orthopaedic metals and their potential toxicity in the arthroplasty patient. Journal of Bone 7 Joint Surgery 2007.
[2] Hart, A. et al. The association between metal ions from hip resurfacing and reduced T-cell counts. J Bone Joint Surg 2006.
[3] Linna, A. et al. Exposure to cobalt in the production of cobalt and cobalt compounds and its effects on the heart. Occup Environ Health 2002.
[4] Vermes, C. et al. The potential role of the osteoblast in the development of periprosthetic osteolysis: review of in vitro osteoblast responses to wear debris… J arthroplasty 2001.
[5] Steens, W. et al. Severe cobalt poisoning with loss of sight after ceramic-metal pairing in a hip: a case report. Acta Orthop 2006.
[6] Pritchett, J. Metallosis of the resurfaced hip 2011.

 

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