Influence of the angle between tibial and prosthesis mechanical axes on tibial bone remodeling in total knee arthroplasty

Osteoarthritis of the knee is one of the most common diseases that affect the quality of life in the elderly population, and Total Knee Arthroplasty is considered the only real treatment for it, and as with any other surgery, a suboptimal technique may lead to an undesirable outcome. This paper aims to investigate the effects of the angle between mechanical axes of the tibia and the implant on the bone remodeling process. A 3D model was reconstructed using CT images, which was then used in an ABAQUS model with a USDFLD subroutine to simulate bone remodeling post TKA. The USDFLD subroutine compares the strain energy density from each increment to that of the previous increment to determine how the bone density will change. Simulation results suggest that when the prosthesis is inclined to one side, stress and density distribution increase, whereas stress and bone density decrease substantially on the opposite side. This decrease in bone density can be as much as 35% in the coronal plane. Sagittal malalignment results suggest that the effect would be relatively localized to the vicinity of the cutting plane. Results suggest uniform load distribution may be achieved when the two mechanical axes are kept parallel, which in turn can lead to decreased prosthesis loosening and bone fractures.