Intentional Femoral Component Flexion – A Method to Balance the Flexion-extension Gap in Navigated Total Knee Replacement

INTRODUCTION: Flexion of the femoral component has been described as a theoretical possibility to balance flexion and extension gap. Computer navigation has made it possible to intentionally flex the femoral component in a controlled fashion to take advantage of the same. Aim: The aim of this study was to assess whether intentional femoral component flexion is helpful in balancing flexion and extension gaps and in restoring sagittal diameter. MATERIALS AND METHODS: One hundred and forty-six total knee replacements performed in a navigated, gap-balanced, and tibia-first technique were included in this study. The femoral component flexion needed to equal flexion to extension gap was calculated based on the navigation data. The sagittal diameter, the anterior, and posterior offset were measured pre- and postoperatively based on the lateral radiographs. Flexion/extension gap differences pre- and postoperatively were analyzed. In addition, pre- and post-operative knee society scores were analyzed. RESULTS: To achieve equal flexion and extension gap, the femoral component was flexed in 95% of patients showing mean flexion of 3.6°. The sagittal diameter was restored in 89%; however, the anterior offset was significantly reduced by 1.3 mm, and the posterior offset was significantly increased by 1.6 mm. The average knee society score improved from 33 preoperatively to 88 postoperatively. CONCLUSIONS: Flexion of the femoral component is indeed an option to balance flexion and extension gap and to restore sagittal diameter in navigated total knee replacement. At present, it is possible only in a navigated technique, but an addition instrument should be made available in the future to reap the benefits of the same in the conventional technique.