Combined proximal tibial osteotomy for varus osteoarthritis of the knee: Biomechanical tests and finite-element analyses.

Background: A special combined proximal tibial osteotomy (CPTO) was designed to correct varus osteoarthritis of the knee with severe intra-articular pathologies, which could not be fully corrected by opening-wedge high tibial osteotomy (OWHTO). The biomechanical strength of the CPTO bone-implant construct was evaluated and compared with those of existing osteotomy methods. Methods: Three variations of osteotomy including OWHTO, tibial condylar valgus osteotomy (TCVO), and CPTO were performed on synthetic bones with locking plate and screws. Wedge stiffness, wedge displacement, and load failure were measured by biomechanical tests. Three types of numerical tibial models were also constructed by three-dimensional model reconstruction software. The stability parameters of the three variations including wedge stiffness, wedge displacement, and stress distribution were further measured by finite-element analyses. Results: The biomechanical testing results revealed that the wedge stiffness, wedge displacement, and failure load of the CPTO construct were very close to those of the OWHTO construct. The numerical results of wedge stiffness and displacement showed good conformity to the previous biomechanical results. The stress distribution at the lateral hinge, the plate corner, and the holes of the CPTO construct were close to those of the OWHTO counterpart, while the stress distribution at the inter-condylar eminence of the tibia and at the middle region of the screws was close to those of the TCVO counterpart. Conclusions: The CPTO construct can provide comparable strength for early mobilization and rehabilitation to that of the OWHTO construct. (C) 2020 Elsevier B.V. All rights reserved.