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

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

Bicondylar tibial plateau fractures pose many challenges in surgical treatment. The aim of the present study was to analyze three methods of reduction, single medial, single lateral, and dual plating, for the treatment of a bicondylar tibial plateau fracture, through finite element analysis (FEA). A simple metaphyseal fracture, type C1.1 (AO-41) was modeled on a CT-derived 3D model of the knee. Lateral and medial proximal tibial polyaxial plates with screws were modeled and placed accordingly for the three methods of reduction. Simulation of physiological type loading corresponding to the maximal weight acceptance phase during a slow walking gait cycle was performed using FEA. Values of stress and strain were recorded near the fracture lines. Dual plating provided a decrease of stress and strain in the tibial plateau area. However, the differences in the values among the three cases were small. The stress concentration areas were located in the vicinity of the fracture, predominantly in the area of the tibial plateau. Considering the limitations of the present study, the results revealed that dual plating leads to smaller stress and strain values near the fracture lines in the tibial plateau area. However, values obtained for single lateral plating are close in range. Considering the complexity of the surgical approach for dual plating, single lateral plating may be a solution for good reduction with fewer surgical risks and complications. Further studies on the C1.1 fracture (AO-41) are needed to analyze the complex issue of reducing and stabilizing such a fracture and to characterize the postoperative state while providing predictable parameters for an optimal result.

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

Background

This study aimed to assess the mechanical static and fatigue strength provided by the FlexitSystem plate in medial opening wedge high tibial osteotomies (MOWHTO), and to compare it to six previously tested implants: the TomoFix small stature, the TomoFix standard, the ContourLock, the iBalance, the second generation PEEKPower and the size 2 Activmotion. Thus, this will provide surgeons with data that will help in the choice of the most appropriate implant for MOWHTO.

Methods

Six fourth-generation tibial bone composites underwent a MOWHTO and each was fixed using six FlexitSystem plates, according to standard techniques. The same testing procedure that has already been previously defined, used and published, was used to investigate the static and dynamic strength of the prepared bone-implant constructs. The test consisted of static loading and cyclical loading for fatigue testing.

Results

During static testing, the group constituted by the FlexitSystem showed a fracture load higher than the physiological loading of slow walking (3.7 kN > 2.4 kN). Although this fracture load was relatively small compared to the average values for the other Implants from our previous studies, except for the TomoFix small stature and the Contour Lock. During fatigue testing, FlexitSystem group showed the smallest stiffness and higher lifespan than the TomoFix and the PEEKPower groups.

Conclusions

The FlexitSystem plate showed sufficient strength for static loading, and average fatigue strength compared to the previously tested implants. Full body dynamic loading of the tibia after MOWHTO with the investigated implants should be avoided for at least 3 weeks. Implants with a wider T-shaped proximal end, positioned onto the antero-medial side of the tibia head, or inserted in the osteotomy opening in a closed-wedge construction, provided higher mechanical strength than implants with small a T-shaped proximal end, centred onto the medial side of the tibia head.