Numerical comparative study of five currently used implants for high tibial osteotomy: realistic loading including muscle forces versus simplified experimental loading

Abstract

BackgroundMany different fixation devices are used to maintain the correction angle after medial open wedge high tibial osteotomy (MOWHTO). Each device must provide at least sufficient mechanical stability to avoid loss of correction and unwanted fracture of the contralateral cortex until the bone heals. In the present study, the mechanical stability of following different implants was compared: the TomoFix small stature (sm), the TomoFix standard (std), the Contour Lock, the iBalance and the second generation PEEKPower. Simplified loading, usually consisting of a vertical load applied to the tibia plateau, is used for experimental testing of fixation devices and also in numerical studies. Therefore, this study additionally compared this simplified experimental loading with a more realistic loading that includes the muscle forces.MethodTwo types of finite element models, according to the considered loading, were created. The first type numerically simulated the static tests of MOWHTO implants performed in a previous experimental biomechanical study, by applying a vertical compressive load perpendicularly to the plateau of the osteotomized tibia. The second type included muscle forces in finite element models of the lower limb with osteotomized tibiae and simulated the stance phase of normal gait. Section forces in the models were determined and compared. Stresses in the implants and contralateral cortex, and micromovements of the osteotomy wedge, were calculated.ResultsFor both loading types, the stresses in the implants were lower than the threshold values defined by the material strength. The stresses in the lateral cortex were smaller than the ultimate tensile strength of the cortical bone. The implants iBalance and Contour Lock allowed the smallest micromovements of the wedge, while the PEEKPower allowed the highest. There was a correlation between the micromovements of the wedge, obtained for the simplified loading of the tibia, and the more realistic loading of the lower limb at 15% of the gait cycle (Pearson’s value r = 0.982).ConclusionsAn axial compressive load applied perpendicularly to the tibia plateau, with a magnitude equal to the first peak value of the knee joint contact forces, corresponds quite well to a realistic loading of the tibia during the stance phase of normal gait (at 15% of the gait cycle and a knee flexion of about 22 degrees). However, this magnitude of the knee joint contact forces overloads the tibia compared to more realistic calculations, where the muscle forces are considered. The iBalance and Contour Lock implants provide higher rigidity to the bone-implant constructs compared to the TomoFix and the PEEKPower plates.

Mechanical strength of a new plate compared to six previously tested opening wedge high tibial osteotomy implants

“…The study showed that the stress distributions in the HTO‐implants that were obtained in loading conditions (1) and (2) were comparable to one another. The stresses in the implants were all lower than the threshold stress values of each implant material (Diffo Kaze et al 2018). This meant that loading the bone‐implant constructs with physiological loads would not lead to critical stresses that could cause implant damage.…”

“…(Maas et al 2013; Diffo Kaze et al 2015; Diffo Kaze 2016; Diffo Kaze et al 2017). The loading of the specimens that was considered for the experimental setup corresponded to a realistic loading of the lower limb during the loading response phase of slow walking (Diffo Kaze et al 2018). The key findings of the present study were the following: (1) The FlexitSystem plate showed sufficient strength for static loading, and average fatigue strength was comparable to the previously tested implants.…”

“…Overall, the thirty-three specimens, whose test results were used in the present study, were subdivided according to the type of test performed, as indicated in Table 3. It has been shown that the loading of the specimens that was used for the experimental setup, corresponded to a realistic loading of the lower limb during the loading response phase of slow walking (Diffo Kaze et al 2018).…”

Treatment of C1.1 (AO‑41) tibial plateau fracture: A finite element analysis of single medial, lateral and dual plating

“…Load simulation was performed in the Simulation Mechanical 2017 software (Autodesk, Inc.). Materials assigned to all parts were considered materials with linear isotropic and elastic mechanical properties and were characterized by Young's modulus and the Poisson's ratio, the values of which are presented in Table I (17)(18)(19).…”

Finite Element Analysis of Three Internal Fixations for the Posteromedial Split Fracture Fragment in Tibial Plateau Fractures

“…Materials were considered with linear isotropic, homogeneous and elastic mechanical properties [18,19]. Details of elasticity modulus of bone structure and plate were listed in Table 2, Poisson´s ratios of 0.3 for all three materials [20,21]. In order to simulate the stress of human tibial plateau, the distal tibia was restrained and xed.…”