Total ankle replacements (TAR) are not as successful as total hip or total knee replacements. A three-time increased revision rate is reported in registry data [1]. Therefrom, wear associated revisions are frequent [2]. However, there is little knowledge about the wear behavior of TAR. This may be partly related to the fact, that currently no standard for wear testing of TAR exists. The aim of this study is to define a biomechanical valid, force-controlled test specification for level walking of TAR. Basic requirements for force-controlled testing of TAR is the definition joint flexion, as well as active forces and torques acting on the joint and the definition of the ligamental stabilization of the joint. To specify flexion of the ankle, gait analysis was performed on patients treated with a TAR (HINTEGRA, Smith & Nephew) using skin mounted markers. Data about in-vivo forces is missing for TAR. Hence, determination of active forces and torques was based on mathematical models as described in the literature. A new testing device (figure 1) has been developed to measure ligamental stabilization of the ankle joint. Measurements were performed on 10 paired cadaver feet (n = 20). Measurements were performed in different flexion angles when applying anterior-posterior forces (± 160N) and internal-external torques (± 2,5 Nm) between the talus and the tibia.Background:
Material and Methods:
There is little knowledge about wear performance of total ankle arthroplasties (TAR). However, revisions rates are high for TAR [1] and wear associated revisions are frequent [2]. Therefore, the aim of this study is
To test the wear behavior of a TAR using a biomechanically valid testing scenario. To test the influence of an alternative ceramic tibial component. To test the long term wear performance of TAR. In the first part of this study the HINTEGRA (Smith & Nephew) TAR has been used for wear testing. Wear testing was performed on a modified AMTI knee simulator. Level walking according to a previous described testing standard [see abstract: Development of a force controlled testing scenario for total ankle replacements] has been used. Level walking was simulated in three clinical relevant situations, first simulating the reduced loading after implantation, secondly simulating an increasing range of motion and at last a loading pattern orientating at the loadings in the native/healthy joint. Every simulation was run for 3 million cycles, resulting in 9 million total cycles. In the second part of this study the metal tibial plateau was replaced by a ceramic tibial component (Biolox® Delta, CeramTec). Simulation was run, as described above, for additional 9 million cycles. Termed as a long term test, in total 18 million cycles of testing are performed.Background:
Material and Methods:
