Effect of posterior cut angle on tibial component loading

Although clinical studies have shown that posterior cut angle affects tibial component stability, biomechanical studies are lacking. Fifteen Sawbones tibiae were divided into 5 groups and prepared with 0°, 3°, 6°, 9°, and −5° tibial surface cuts, and a tibial component was implanted with cement. Using a standard and then a highly congruent polyethylene insert, the knee was loaded at 0° and 30° of flexion. There were statistically significant increases in anterior micromotion of the standard polyethylene component for each increase in posterior slope cut angle, which increased for the highly congruent polyethylene component. The anterior slope cut (−5°) led to significant posterior micromotion of the tibial polyethylene component. Increased posterior slope cut angle significantly decreased tibial anterior compressive strains and significantly increased tibial posterior compressive strains. The highly congruent insert significantly increased this posterior strain. The results indicate that cutting the articular surface of the tibia at a 0° or 3° posterior slope provides the greatest tibial component stability.