Custom-fit total knee arthroplasty (OtisKnee) results in malalignment

We report on 4 patients who underwent total knee arthroplasty with OtisKnee system (OtisMed, Hayward, Calif). An image-free computer navigation system was used to evaluate the deformities and the recommended ruts. The recommended custom cuts were as follows: valgus/varus cuts on the femur (5.5 degrees valgus to 0.5 degrees varus) in reference to the mechanical axis, flexion cuts on the femur (4 degrees-9 degrees of flexion); femoral rotation was within 1 degrees of the epicondylar axis; valgus/varus cut on the tibia (3 degrees of valgus to 7.5 degrees of varus); tibial slope (5.5 degrees of anterior slope to 0.5 degrees of posterior slope). The custom OtisKnee system guides recommended alignment of the components that was more than 3 degrees off of mechanical axis. The potential for malalignment with this system places implants at high risk of early failure.