Investigation of a painful joint prosthesis

Pain in a previously painless artificial joint may be symptomatic of infection or loosening.

It is said that:

• the pain of infection is bad at night
• the pain of loosening is worst first thing in the morning

The following investigations should be performed:

• radiographs:
  • infected or loose prostheses are surrounded by a radiolucent rim
  • scalloping of the surrounding cortex may indicate infection or the foreign body response to a loose joint
    
    
• blood tests:
  • blood tests cannot distinguish infection and loosening
  • white cell count is usually normal
  • the ESR may be raised to 30-50 mm/h
    
    
• isotope scans:
  • technetium-99m highlights infection and loosening
  • indium scans may specifically show infection
    
    
• aspiration:
  • sterile aspiration does not exclude infection
  • aspiration should be performed with full aseptic technique in an operating theatre