Presentation
Worsening left hip pain following left hip resurfacing.
Patient Data
Previous left hip joint metal on metal prosthesis (Birmingham). There is asymmetry of the femoral head component within the acetabulum consistent with component wear. Expansile lesion in the left superior pubic ramus measures around 3-4 cm. There are further well defined lytic lesions in the acetabulum and around the femoral stem. These are likely to be granulomas related to particle disease.
Note is made of undercoverage of the right femoral head with an upward sloping acetabulum indicating mild right acetabular dysplasia with secondary degenerative change.
At left hip revision surgery, there was metallosis in the soft tissues, synovitis and lytic granulomas in the pubic bone, ischium, femoral neck and acetabulum.
Pathology:
Fibrous capsule with attached adipose tissue and skeletal muscle. The fibrous tissue contains numerous pigmented macrophages. No acute inflammatory or neoplastic features are identified.
Case Discussion
Metal on metal prostheses were reintroduced for total hip replacements mainly for younger people because they were associated with greater hip stability, preserved the femoral neck and part of the femoral head, and consequently optimized stress transfer to the femur 1.
However recent studies have shown failure rates of 16 % by 10 years post implantation. Failure is commonly associated with granuloma formation (metal on metal pseudotumor) that is thought to be due to soft tissue reaction to nanometer sized metal particles 1.
In many countries, these prostheses have now been withdrawn from the market.
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