Surgical procedure
knee arthroplasty, TKA
All patients received a cemented posterior stabilized NexGen LPS Flex TKA (Zimmer, Warsaw, Indiana, USA). Participants randomized to the conventional group received a TKA implanted using standard instrumentation, whereas those randomized to the navigated group had surgery using the iNav portable EM navigation system (Zimmer GmbH, Winterthur, Switzerland and Medtronic, Minneapolis, MN, USA). A standard process of joint registration maps the surface anatomy of the joint. All surgeries including joint surface registration were carried out by, or under the direct supervision of, one of two knee arthroplasty surgeons. Alignment targets were similar in both groups with a neutral HKAA and the aim to implant both femur and tibial components perpendicular to this in the coronal plane. There was no statistically significant difference in post-operative component alignment between the two groups (Fig. Comparison of post-operative accuracy of component placement in each plane and post-operative mechanical axis alignment as measured from CT scans. Dotted line represents the 3° target window for the mechanical axisLigament balancing was carried out using clinical assessment during the surgical procedure in both groups. In the navigated group, additional information was provided by the system with real-time feedback on the gap in mm between the femoral and tibial component and of the overall HKAA during varus and valgus stress.