The bone cuts and ligament balance in total knee arthroplasty: The third way using computer assisted surgery

Computer assisted orthopaedic surgery has become an important innovation in total knee arthroplasty (TKA) with very good clinical results and more reproducible and reliable implant positioning. However there is additional useful data that is recorded during the surgical procedure that can be used to develop new ways in performing the replacement. In TKA one of the main goals is to obtain flexion/extension gap equivalence where the geometry of flexion and extension gaps are homothetic. The gaps are created by the bone cuts and any soft-tissue releases that are performed, with the sectioning occurring in a structured order. Both mechanical devices and navigation with a computer can be used as aids in achieving gap equivalence. It is essential to have an instrumentation system that can be used for conventional as well as for computer assisted surgery so the surgeon can choose either, and also as a back-up if there are technical problems with the computer system. This allows changing to a conventional TKA without having to change the instrumentation.