Computer assisted orthopedic surgery; its influence on prosthesis size in total knee replacement

Improvement of alignment and position of the components in TKAs using Computer Assisted Orthopaedic Surgery (CAOS) has been described. However, much less is known about the accuracy of CAOS in determining the size of the components. The purpose of this study was to evaluate the size of the femoral and tibial component using the CAOS system from Brainlab. The component sizes were compared to pre-operative templating and post-operative scoring the adequateness of size. Forty TKAs (NexGen) were evaluated: 20 using CAOS and 20 conventional. Statistical analysis of the templated and implanted size indicated a fair agreement for the femur (kappa 0.38) and the tibia (kappa 0.35). In the CAOS group significantly more oversizing occurred for the femoral component (p = 0.020). No significant difference was found for the tibial component. We conclude there is a risk of oversizing the femoral component of the NexGen system when using CAOS.