Computer navigation of soft tissues in total knee replacement: optimizing knee kinematics

Background The use of computer navigation in total knee replacement (TKR) has resulted in consistently accurate alignment of prosthetic components. Intraoperative assessment through the range of motion of the knee and stress testing also is possible. Dedicated navigators are now quite keen to assess soft tissues objectively along with limb alignment during TKR. Methods Our computer navigation system was designed to produce a graphical output of varus and valgus deviation of the knee against the degree of flexion. We undertook a retrospective analysis of such graphs in 77 TKR that were part of a prospective randomized trial comparing two soft-tissue balancing techniques in TKR. Results We noted that different osteoarthritic knees produced four different types of passive range of motion graphs. A total of 24.6% knees in our series demonstrated unusual passive kinematics. Characteristics of each subtype were retrospectively analyzed. The use of two tissue balancing techniques within our trial demonstrated their effect on different types of knees. Conclusions We believe that up to one fourth of knees presenting for TKR present difficulties in achieving good soft-tissue balance because of varied kinematics, which in turn could be the result of morphological features. Computer navigation assistance helps identify these before undertaking bone cuts. The future will bring forth different techniques to suit different types of knees in order that consistent optimal results are obtained in all TKR.