Treatment Injury

Failure of hip replacement, metallosis reaction

Erika, an active 57 year-old, had a right total hip joint replacement two years ago after suffering from osteoarthritis for several years.

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Event: Failure of hip replacement.
Injury: Metallosis reaction.

Key points

  • Metallosis is a commonly used term for deposition of metal debris in periarticular tissues after metal on metal hip replacement prosthesis.
  • Not all metallosis reactions are symptomatic.
  • Symptoms may include groin pain, stiffness and occasionally swelling after hip joint replacement surgery
  • Blood tests show highly elevated plasma chromium and cobalt levels due to Adverse Reaction to Metal Debris (ARMD)
  • Revision surgery is commonly required – but brings its own new risks.
  • Findings at surgery include tissue staining, fluid or granuloma formation, loosening, and bone loss.
  • The New Zealand Orthopaedic Association Metal on Metal information Update can be found here.

Case Study

She had been diagnosed with acetabular dysplasia on her right side, but was usually fit and had a slim build. She had recently had a cholecystectomy for gallstones and took omeprazole for gastro-oesophageal reflux.

At the time of her hip replacement the surgeon elected to use a metal-on-metal prosthesis. The procedure was uncomplicated and Erika recovered well with a good range of motion. She was able to get back to exercising and was happy with the result.

One year later, however, she began to have pain in her hip when walking. This progressed over the next twelve months to the point that she was unable to walk for more than 15 to 20 minutes before the pain in her left hip and groin became unbearable.

She was referred by her GP back to her orthopaedic surgeon, who suspected a metallosis reaction. An ultrasound scan was organised and blood tests were taken.

The blood tests showed highly elevated plasma chromium and cobalt levels. The ultrasound scan showed extensive abnormal soft tissue thickening involving the iliopsoas tendon secondary to a likely metallosis reaction.

A decision was made to replace the hip prosthesis with a ceramic on ceramic implant. It was found at the time of surgery that the metal acetabular cup was more vertically-oriented than ideal.

A treatment injury claim was lodged for the metallosis reaction necessitating replacement of the hip prosthesis. ACC accepted the claim and was able to contribute to the costs of Erika’s additional treatment.

Commentary

Dr. William Taine, BChB, FRACS (Orthopaedics)

Metallosis is the commonly used term for deposition of metal debris in periarticular tissues after metal on metal hip replacements. It is also seen in cases of failure in other joint replacements where metal on metal abrasion occurs. The term could also be used to refer to the rise in serum metal ions that occurs in patients after this type of surgery. It is part of a spectrum of reactions seen in response to metal wear, collectively called Adverse Reactions to Metal Debris (ARMD). These reactions include an apparent hypersensitivity response (aseptic lymphocytic vasculitis associated lesions, or ALVAL), where a lymphocytic response dominates, to pseudotumour formation, a solid or cystic granulomatous mass where a macrocytic response dominates.

All artificial bearings undergo wear, regardless of the material used. Hard on hard bearings, using ceramic or metal, generate large numbers of very small particles, with little volumetric wear. In most circumstances this does not affect the long term outcome. The traditional metal on plastic (ultra high molecular weight polyethylene) bearings generate smaller numbers of larger particles, which results in more loss of volume, an inflammatory response, and may eventually lead to loosening. A number of factors are associated with greater than expected wear, such as alignment, contact patterns and area, design and material, and activity levels.

Metallosis and pseudo tumours result when the particle load from a metal on metal bearing is excessive. They have been associated with edge loading, where a reduced contact area occurs at or near the rim of the cup. Design factors such as a shallow cup and reduced clearance between the head and socket will influence this, as well as having an effect on fluid film lubrication in the bearing. Also, alignment may play a potentially important role. Both the cup inclination (the angle from the horizontal) and ante version (the forward facing angle) have an effect.

Not all ARMD reactions are symptomatic. In those that are, symptoms may include groin pain, stiffness and occasionally swelling. Aspiration and measurement of inflammatory markers may be required to rule out infection. Investigation by x-ray may show any alignment issues, loosening or autolysis, and an effusion or a soft tissue mass on ultrasound(U/S). CT or MRI with artefact reduction may show similar findings. Serum ion levels are usually but not always more elevated than the expected increase in patients with these implants. Revision is commonly required, and findings at surgery include tissue staining, fluid or granuloma formation, loosening, and bone loss.

References

  1. Haddad et.al.(2011). Metal on Metal Bearings: the evidence so far. JBJS 93B: 572-9.
  2. Holland et al. (2012). Ten Year Clinical, Radiological and Metal Ion Analysis of the Birmingham Hip Resurfacing. JBJS 94B: 471-6.
  3. Kwon et al. (2010). Analysis of wear of Retrieved Metal on Metal Hip Resurfacing Implants Revised due to pseudotumours. JBJS 92B: 356-61.
  4. Williams et al. (2011). Prevalence of pseudotumour in Asymptomatic Patients after Metal on Metal Hip Arthroplasty. JBJS 93A: 2164-71.

Claims Information:

Between 1 July 2005 and 5 May 2012, ACC received 14 claims relating to metallosis reactions due to Mitch THR and De Puy ASR acetabular hip prosthesis.

The main reasons for the recall of the prosthesis or revision surgery were metal ion hypersensitivity reaction and loosening or failure of the hip prosthesis.

About this case study

This case study is based on information amalgamated from a number of claims. The name given to the patient is therefore not a real one. The case studies are produced by ACC’s Treatment Injury Centre, to provide health professionals with:

  • an overview of the factors leading to treatment injury
  • expert commentary on how similar injuries might be avoided inthe future.

The case studies are not intended as a guide to treatment injury cover. Send your feedback to: TI.info@acc.co.nz

How ACC can help your patients following treatment injury

Many patients may not require assistance following their treatment injury. However, for those who need help and have an accepted ACC claim, a range of assistance is available, depending on the specific nature of the injury and the person’s circumstances. Help may include things like:

  • contributions towards treatment costs
  • weekly compensation for lost income (if there’s an inability to work because of the injury)
  • help at home, with things like housekeeping and childcare.

No help can be given until a claim is accepted, so it’s important to lodge a claim for a treatment injury as soon as possible after the incident, with relevant clinical information attached. This will ensure ACC is able to investigate, make a decision and, if covered, help your patient with their recovery.

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Published 01/10/2012

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