CAOS in mobile bearing tibia cut first total knee arthroplasty

Abstract

Mobile bearing total knee arthroplasty was initially introduced by Goodfellow with the concept of allowing greater mobility of the polyethylene insert while maintaining very high articular surface conformity with the idea of producing better wear characteristics. Buechel and Pappas developed the Low Contact Stress mobile bearing design in 1977 developing this concept into a system of devices that allowed for a variety of similar implants and surgical techniques. For many surgeons around the world, this concept has stood the test of time, offering favorable wear characteristics and more adaptable prosthetic knee kinematics. Stiehl et al. have performed a number of kinematic evaluations of mobile bearing total knees finding mobile bearing devices to be typical of all total knee arthroplasties, with a significant variation of condylar surface translations, condylar liftoff and screw-home rotation. Perhaps the most unique aspect of the mobile bearing device is the ability to allow for unrestricted femoral tibial rotation of the polyethylene insert. In addition, uncoupling the modular tibia allows the surgeon to have significant freedom from errors that may arise from mal-rotation of the tibial component, often leading to such problems as patellar subluxation, tibial post wear, and catastrophic posterior medial implant wear. After total knee arthroplasty, fluoroscopic video kinematic studies have demonstrated that while some cases demonstrate the expected internal rotation with knee flexion, others will actually exhibit paradoxical external rotation with knee flexion. Computer assisted surgical navigation (CAOS) offers a unique opportunity to evaluate tibial rotation along with numerous other parameters such as mechanical alignment, joint flexion, ligamentous balance, and tibial axis alignment in flexion. This chapter describes an experience evaluating the data gathered from a large number of cases where tibial rotation was specifically documented before and after total knee arthroplasty in a group of patients where the «tibial cut first» method was utilized. © 2007 Springer Medizin Verlag Heidelberg.