The influence of an extra-articular implant on bone remodelling of the knee joint.

Bone remodelling is a crucial feature of maintaining healthy bones. The loading conditions on the bones are one of the key aspects which affect the bone remodelling cycle. Many implants, such as hip and knee implants, affect the natural loading conditions and hence influence bone remodelling. Theoretical and numerical methods, such as adaptive bone remodelling, can be used to investigate how an implant affects bone mineral density (BMD). This research aimed to study the influence of an extra-articular implant on bone remodelling of the knee joint using adaptive bone remodelling. Initially, a finite element (FE) model of the knee joint was created. A user-defined material subroutine was developed to generate a heterogeneous BMD distribution in the FE model. The heterogeneous density was then assigned to the knee model with the implant in order to investigate how the implant would affect BMD of the knee joint, five years postoperatively. It was observed that in the medial compartments of the femur and tibia, bone mineral density increased by approximately 3.4% and 4.1%, respectively, and the density for the fixation holes of both bones increased by around 2.2%. From these results, it is concluded that implanting of this load-sharing device does not result in significantly adverse BMD changes in the femur and tibia.