Biomechanical study of a new rim plate fixation strategy for two kinds of posterolateral depression patterns of tibial plateau fractures: a finite element analysis.

PURPOSE

The biomechanical capacity of "Barrel Hoop Plate (BHP)" in the treatment of the posterolateral tibial plateau (PL) depression fractures remains unknown. In this study, two kinds of posterolateral tibial plateau depression models involving mild slope-type depression fracture (MSDF) and local sink hole-type depression fracture (LSDF) were created to test and compare the biomechanical capacities of BHP with the other two conventional fixations (Anterolateral Plate and Posterolateral Plate, ALP and PLP) by finite element analysis.

METHODS

The 3D models of three kinds of plate-screw systems and the two kinds of PL-depression models (MSDF and LSDF) were created. An axial force of 400N was applied from the distal femur to the tibial plateau. The maximal displacements of the posterolateral fractures (PLFs), the distribution on the PLFs articular surface and key points displacements were measured. Stresses in the fixation complex including the maximal Equivalent (von-Mises) Stress of implants, the max shear stress of PLFs and stiffness of the fixation were calculated.

RESULTS

The maximal displacement of MSDF was least in Group BHP. The maximal displacement of LSDF was least in Group ALP. In MSDF, BHP showed the best rim fix effect in MSDF, but unsatisfactory results in LSDF. In both MSDF and LSDF, the greatest max Equivalent Stress of the plate and the screw occurred in the PLP system. ALP and BHP showed a comparable stiffness in MSDF and ALP had the strongest stiffness in the fixation of LSDF.

CONCLUSIONS

In MSDF, the BHP has the best biomechanical capacity, especially in displacements of key points such as the PL rim, fracture line, and depression center. In LSDF, the ALP system shows the best biomechanical effect. Although the PLP has the best fixation effect on the posterior wall, it is not suitable for PL-depression fracture fixation.