Implant design and techniques for patellar resurfacing in total knee arthroplasty

There are two basic techniques for resurfacing of the patella in total knee arthroplasty. The inset patellar component recesses a circular dome with a single fixation peg into a reamed patella while the onlay component is placed onto the cut surface of patella. Onlay patellar components have a wide variety of shapes, designs, and methods of fixation. There are differences in technique and possible complications with the inset and onlay patellar components. However, neither method has proved to be superior. Fixation of an onlay patellar component is usually with cement, but successful cementless porous-coated designs exist. Fixation of an all-polyethylene patellar component occurs by cementing a component with either a single central peg or three smaller peripheral pegs; although one method is not preferred over the other, there have been reports of breakage with three pegs. The design and fabrication of these components are important to prevent peg breakage with repeated shear stress. There are few clinical data implicating the different shapes or methods of patella component fixation with the complications of anterior knee pain, wear, patella fracture, and component breakage. Attention to detail during surgery is likely the most critical factor to the success of patellar resurfacing in total knee arthroplasty.