Biomechanical effects of screw orientation and plate profile on tibial condylar valgus osteotomy - Finite-element analysis

Homogeneous material models can overestimate stresses in high tibial osteotomy: A finite element analysis

Although widely used numerical models can assess the stability of lateral hinges in high tibial osteotomy (HTO) and may provide acceptable results in comparative studies, accurate stress prediction may not be possible due to simplified homogeneous models of the bone. The present study aimed to investigate the effect of a heterogeneous versus four homogeneous models on the results of stress and force. Each of the four homogenized FE models utilized the same elastic modulus of 16,700 MPa for the cortical while employing a single elastic modulus varying from 155 to 5000 MPa for the cancellous. In heterogeneous model, the modulus of each element was assigned using the bone density. It was found that stresses at the hinge in homogeneous models were higher than those in the heterogeneous model. The maximum principal stress (MPS) was 437 MPa for the heterogeneous model while that was 2179, 2351, 2581, and 2637 MPa for the homogeneous models with the elastic moduli of 155, 500, 2130, and 5000 MPa, respectively. Also, the opening force was 150 N for the heterogeneous model significantly lower than 649-1534 N range predicted for the homogeneous models. The use of a homogeneous model in the FE analysis of HTO overestimated the stresses and force. Thus, in addition to casting doubt on the use of a single modulus in the numerical analysis of HTO, Future HTO studies can use our results as a benchmark for comparison purposes and highlight the use of patient-specific bone density - elastic modulus relation in simulation.

Biomechanical evaluation of combined proximal tibial osteotomy for varus knee osteoarthritis implanted novel designed plate system: Finite element analysis

BACKGROUND

Combined proximal tibial osteotomy (CPTO) is an innovative and effective procedure for correcting varus knee osteoarthritis (VKOA) with intra- and extra-articular deformity. Here, we designed a novel internal fixation plate system for CPTO and assessed the biomechanical strength of the bone-implant.

METHODS

Our newly designed CPTO internal fixation plate system included a specialized plate shape, combination holes, locking screw holes, screw position, and size of fixation. The biomechanical performance of this plate system in CPTO treatment was compared via finite element analysis (FEA) to traditional Tomofix devices implanted in the opening-wedge high tibial osteotomy (OWHTO), tibial condylar valgus osteotomy (TCVO), and CPTO.

RESULTS

The tibial wedge stiffness and displacement after CPTO implantation of the novel internal plate fixation increased by 9.6%, which was -65% higher than the CPTO with the Tomofix system. The average stress of the bone, plate, and screws in the CPTO implanted the novel designed plate system compared to the Tomofix system decreased by 12.7%, 1.9%, and 20.3 %, respectively. The device maximum stress and wedge stiffness after CPTO with the novel plate system versus traditional OWHTO and TCVO with the Tomofix system were 255.7 MPa, 204 MPa, 130.4 MPa, and 678.9 N/mm, 660.3 N/mm, 1626.0 N/mm, respectively.

CONCLUSIONS

The novel internal fixation plate system usage during CPTO exhibited similar bone-implant biomechanical strength, compared to OWHTO, but with enhanced construct stability.