Partial knee replacement - Patellofemoral Replacement

This is an xray of a partial knee replacement. The specific type of partial knee replacement is a " patellofemoral arthroplasty" or replacement of the knee cap and the femoral groove in which the knee cap tracks. The knee on the right has been surgically corrected, including the centering of the knee cap on the femoral groove. I prefer to use Computer Surgical Navigation when performing this operation which results in a more accurate placement of the components in the knee which results in better function of the knee and a longer lasting partial knee replacement (up to 20 years). The knee on the left is severely arthritic and is malpositioned. The malpositioning or lateral tracking of the patella, along with recurrent patellar dislocations, caused this patient's knee caps to wear out prematurely.