Fig. 3From: Changes in femoral rollback and rotation with increasing coupling in knee arthroplasty—a biomechanical in-vitro studyDetermination of the femoral axis. A A cylindrical axis was defined by identifying the femoral condyles as geometrical ridge-regions (red) using a curvature-based algorithm (Subburaj, Ravi [33] and (B) subsequent fitting of spheres [22] (red: medial sphere; blue: lateral sphere)Back to article page