Rotation of the femoral and tibial component is critically important to patellar tracking. Neutral or external rotation of the tibial component in relation to the tibia decreases the Q angle and assists in the tracking of the patella. The patella is subjected to high mechanical pressures, and this leads to the risk of patellar fracture. The aim of the technique is to restore overall, patellar thickness, while maintaining l5 mm of patellar bone thickness. It is commonly believed that the resurfaced patella must be restored to the normal thickness.
Patellar thickness is measured with a calliper using the central portion of the patella.
The use of a cutting guide prevents over- or underresection and is more likely to be reproductible. The thickness of patellar implants ranges from 8 to 10 mm. In the case of a thin or sclerotic patella it may be advisable to avoid resurfacing. Other factors that may affect incidence of patellar fractures include the position of the joint line, alignment, design of the prosthetic trochlea, and sagittal position of the femoral component. The goal is to obtain a flat, symmetrical patellar resection.