Follow-Up Studies
Painful or failed knee arthroplasties are evaluated with serial conventional radiographs. Most of these cases will show radiographic abnormalities. Exceptions include:
- Acutely infected arthroplasties where the diagnosis has been made very early by clinical exam and arthrocentesis, before radiographic abnormalities have developed
- Subtle rotational malalignment, which are better demonstrated on CT
Painful or failed arthroplasties may be due to a variety of problems (Table 1). These include:
- Instability
- Polyethylene problems
- Osteolysis
- Loosening
- Infection
- Fractures
- Patellar complications
- Heterotopic ossification
- Malalignment
These and other conditions frequently require revision arthroplasty. In 1999, 22,000 knee revision operations were performed in the United States.8
Table 1: Percentage of patients with failure mechanism stratified into early and late subgroups.9 (PE=Polyethylene)
