Abstract
The ligament balance as well as the alignment is essential for successful total knee arthroplasty (TKA). However it is usually assessed and adjusted only at 0? and 90?. In order to evaluate the ligament balance at the other angles we have used a navigation system. Twenty-one patients underwent posterior stabilised mobile bearing TKA using a CT-based navigation system were included in this study. Immediately post-operation and still under anaesthesia, varus and valgus stresses were applied on operated knees manually at 0?, 30?, 60?, 90? and 120?. The ligament balance was calculated based on the angles under varus and valgus stress displayed on the navigation screen, presenting a relationship between the femoral and tibial cutting planes. The mean ligament balance angle at 0?, 30?, 60?, 90? and 120? were −2? ± 3.6?, −5.8? ± 7.9?, 5.0? ± 6.9?, −1.3? ± 5.4?, 7.9? ± 7.2?, respectively. At 0? and 90? balance was well adjusted, however in the other angles, it was quite varied. At 30? and 120?, the lateral side was loose, on the other hand, medial side was looser at 60? knee flexion angle. The good balance at 0? and 90? is understandable because the balance is assessed and adjusted in these angles. Regarding the other angles, the 30? and 120? results corresponded with previous studies; however, the 60? results did not correlate. Although the reason is unknown, it must be aware the mid-flexion and deep flexion instability is quite common. Further investigations about the impact on clinical outcomes of such instabilities and how to adjust them if they are critical are needed.
