Maurilio Marcacci
Rizzoli Orthopedic Institute, Italy
Title: Surgical technique based on instantaneous flexion axis and vectorial dynamic analysis
Biography
Biography: Maurilio Marcacci
Abstract
Providing correct rotational alignment of femoral component in total knee arthroplasty (TKA) is mandatory to achieve correct kinematics, good ligament balance and patellar tracking. Anatomical techniques are based on the acquisition of several landmarks, such as the transepicondylar line, the line tangent to the posterior condyles and the Whiteside line. Their localization is quite variable and surgeon dependent, which can lead to miscalculation in component positioning. Conversely, functional techniques identify functional references. These references are subject and joint-specific and depend only on the performed movement and not on the identification of specific anatomical landmarks. One of the methodologies already used in navigated TKA and based on a functional technique is the ‘‘functional flexion axis (FFA)’’ that aims to describe the motion of a rigid body as a rotation around and a translation along an instantaneous axis of rotation. On axial plane, osteoarthritis does not influence the evaluation of FFA, compared with healthy subjects. On the contrary, some differences have been found on frontal plane. Moreover, FFA changed significantly after TKA in the frontal plane, while in the axial plane, there was no difference between pre- and postoperative conditions. Finally, the position of the functional axis on frontal plane in preoperative conditions is dependent on native limb alignment, while on axial plane is not dependent on the amount of preoperative varus deformity. We concluded that this method reported good repeatability, demonstrating its usefulness for clinical purposes particularly to evaluate rotational positioning of the femoral component in the axial plane.