Influence of anteroposterior and mediolateral instability on range of motion after total knee arthroplasty: An ultrasonographic study

Ultrasonographically, the femoral component and the tibial plate of total k nee prostheses are strongly echogenic, while the high-density polyethylene insert is hypoechoic. This study evaluated the influence of mediolateral an d anteroposterior stability after total knee arthroplasty (TKA) on range of motion using realtime monitoring with ultrasound. Mediolateral stress tran slation, which is increased by horizontal resection of more bone at the end s of the femur or tibia for easy prosthesis implantation, was examined on c oronal scans at the level of the collateral ligaments. Anteroposterior draw er was examined on sagittal scans at the level of the patellar tendon. Medi olateral translation (0-10 mm; mean 2.24 mm) did not correlate with range o f motion, while anteroposterior drawer (2-10 mm, mean 5.05 mm) correlated w ell with range of motion. These ultrasonographic findings suggest that horizontal over-resection of t he ends of the femur and tibia contributed to joint laxity, which would not result in better ROM. Rollback and sliding of the femoral component on the tibia, which is believed to be correlated with anteroposterior drawer, may be important in achieving better range of motion and obtaining excellent r esults in TKA.