Clinical History, Examination and Blood Test Results 

  • Step 1 case 1 is a 66-year old lady who presented in January 2015 with a severely painful right hip replacement. She had bilateral metal-on-metal Pinnacle S-ROM total hip replacements in 2007 and 2009 for the right and left hip respectively. She had mild pain in the right hip since 2011. She used a stick for walking.

  • Her Oxford hip scores were 17/48 and 29/48 for right and left hips respectively.

  • Examination of her right hip revealed very irritable hip movements with a reduced range. She was able to straight leg raise with difficulty causing considerable pain.

  • Blood ESR was 26mm/Hr and CRP was 10mg/L. Blood metal ion levels were 2.8 ppb (48nmol/L) and 3.5 ppb (26nmol/L) for cobalt and chromium respectively.

  • Metal artefact reduction sequence (MARS) MRI revealed a pseudotumour posterior to the right hip (see below)

  • An aspiration was performed, because the CRP was greater than or equal to 10 mg/L, and showed no growth after extended cultures.


Imaging Results

PRE-OP RADIOGRAPH

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This anteroposterior (AP) radiograph of the pelvis demonstrates bilateral well fixed and well positioned S-ROM Pinnacle MOM hip replacements. Both cups appear stable and well positioned,

PRE-OP MARS MRI

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The patient had a pre-operative metal artefact reduction sequence (MARS) MRI revealing a pseudotumour posterior to her right hip. 


Diagnosis

  • Adverse reaction to metal debris (ARMD) of the right hip as a result of the metal on metal (MOM) bearing in used in the S-ROM MOM Pinnacle hip replacement.


Treatment

  • This patient required a right sided liner exchange to ceramic on polyethylene (COP) bearing with pseudotumour excision.

  • Key surgical operative steps included

    • Posterior approach

    • Joint lining and pseudotumour excised where possible

    • 5 hip capsule tissue samples sent for extended microbiological culture

    • Femoral head extracted (this is usually straight forward for S Rom stems but there is cold welding of some stems such as the Biomet Taperloc with Magnum heads in which case prepare for stem extraction)

    • Metal liner extracted using the Depuy alternate bearing (AB) extractor

    • 52mm polyethylene liner implanted

    • 36mm ceramic head with titanium sleeve

    • Washout


Imaging Outcomes

POST-OP RADIOGRAPH

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The head bearing surface is visible on the right side because the right acetabular liner is now made of polyethylene. The left side which has a retained MoM bearing.

 

Clinical Outcomes

  • Revision surgery was performed in May 2016. 1 year post operative the left side is becoming more symptomatic so will require a similar procedure in the future.


Learning Points

  • Components, such as the acetabular shell and femoral stem, can be retained if they are: well fixed to bone; well orientated; and not infected.