The number of total hip arthroplasties in young patients is continuosly increasing. Nowdays, the study of the materials wear, with the goal of improving the survivorship of implants, represents a fundamental subject in this kind of surgery. The role of ceramic materials in the valutation of types of wear is particularly known. We have selected 834 patients, underwent total hip arthroplasty, in which a ceramic head was impalnted with a maximum follow up of ten years. 367 patients were males and 467 were females, operated by 14 surgeons of the same equipe of Orthopaedic and Traumatology Department. A postero-lateral approach, according to Gibson Moore, and an extrarotator tendons transosseal repair was performed.Introduction
Materials and Methods
Providing proper rotational alignment of femoral component in total knee arthroplasty is mandatory to achieve correct kinematics, good ligament balance and proper patellar tracking. Recently functional references, like the function flexion axis (FFA), have been introduced to achieve this goal. Several studies reported the benefits of using the FFA but highlighted that further analyses are required to better verify the FFA applicability to the general clinical practice. Starting from the hypothesis that the FFA can thoroughly describe knee kinematics but that the joint kinematics itself can be different from flexion to extension movements, the purpose of this study was to analyse which factors could affect the FFA estimation by separately focusing on flexion and extension movements. Anatomical acquisitions and passive joint kinematics were acquired on 79 patients undergoing total knee arthroplasty using a commercial navigation system. Knee functional axis was estimated, from three flexion and extension movements separately acquired included in a range between 0° and 120°. For flexion and extension, in both pre- and post-implant conditions, internal-external (IE) rotations was analysed to track any changes in kinematic pattern, whereas differences in FFA estimation were identified by analysing the angle between the FFA itself and the transepicondylar axis (TEA) in axial and frontal plane.Introduction
Methods
Several methods, based on both functional and anatomical references, have been studied to reach the goal of a proper knee kinematics in total knee arthroplasty (TKA). However, at present, there is still a large debate about which is the most precise and accurate method to achieve the correct rotational implant positioning. One of the main methods already used in TKA to describe the tibiofemoral flexion-extension movement, based on a kinematic technique, thus not influenced by the typical variability related to the identification of anatomical references, is called “functional flexion axis” (FFA) method. The purpose of this study was to determine the repeatability in estimating knee functional flexion axis, thus evaluating the robustness of the method for navigated total knee arthroplasty. Passive kinematic and anatomical acquisitions were performed with a commercial navigation system on 87 patients undergoing TKA with primary osteoarthritis. Knee FFA was estimated, before and after implant positioning, from three flexion-extension movements between 0° and 120° (Figure 1). The angle between Functional Flexion Axis and an arbitrary clinical reference, the transepicondylar axis (TEA), was analysed in frontal and axial view (Figure 2). Repeatability Coefficient and Intraclass Correlation Coefficient (ICC) were estimated to analyse the reliability and the agreement in identifying the axis.Introduction
Methods
