Clinical History, Examination and Blood Test Results

  • This 58 year-old male had a previous bilateral metal-on-metal hip replacement via lateral approaches (performed to treat arthritis).
  • He developed painful hips four years later, with severe restriction in mobility.  His Oxford Hip Score was 15/48.  Blood tests revealed raised cobalt ion levels (21.2ppb), a raised ESR (48mm/h) and CRP (12mg/L).  Hip aspiration was negative for infection.


Imaging Results

PRE-OP RADIOGRAPH

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The pre-op radiograph doesn't reveal anything significant

 

PRE-OP MRI

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There is marked significant muscle damage affecting both hip abductors.

 

MoM EXAMPLE - BIRMINGHAM

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Birmingham hip replacement with a Synergy stem (Smith & Nephew). This is made of a Cobalt-Chromium alloy.

MoM EXAMPLE - ADEPT

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Adept hip replacement with a Spotorno stem (Zimmer). This is made of a Cobalt-Chromium alloy.


Diagnosis

  • Bilateral hip abductor atrophy due secondary to metallosis from two cobalt chromium total hip replacements.


Treatment

INTRAOPERATIVE CUP EXTRACTION

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CERAMIC HEADS

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These are intraoperative images of the cup being extracted.

The original stems were retained, and the old metallic head was replaced with a ceramic head.  The acetabular shell was replaced and a new liner inserted.


Imaging Outcomes

POST-OP RADIOGRAPH 

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The left stem has been retained. The left femoral head has been replaced with a ceramic one. The acetabular cup has been revised and a polyethylene liner has been used.

 

Clinical Outcomes

  • The patient is happy with their revision surgery and is now pain free on the left side.


Learning Points

  • When abductor muscle damage is detected it can be due to either the surgical approach (lateral approach causing direct damage and potentially denervation injury) or local toxic reaction of cobalt ions (in metal debris disease).

  • Markers of inflammation in the blood (CRP/ESR) can be raised in infection and metal debris disease.  Fluid aspirated from the hip joint is an important pre-operative investigation to establish whether it is due to infection or not.