Development and analytical validation of a finite element model of fluid transport through osteochondral tissue

Abstract

Fluid transport between cartilage and bone is critical to joint health. The objective of this study was to develop and analytically validate a finite element model of osteochondral tissue capable of modeling cartilage-bone fluid transport. A biphasic viscoelastic model using an ellipsoidal fiber distribution was created with three distinct layers of cartilage, superficial zone, middle zone, and deep zone along with a layer of bone. For stress-relaxation in unconfined compression, our results for compressive stress, radial stress, effective fluid pressure, and elastic recoil were compared with established biphasic analytical solutions. Our model also shows the development of fluid pressure gradients at the cartilage-bone interface during loading. This model is the first to capture fluid pressure gradients at the cartilage-bone interface for unconfined compression. These results provide additional evidence that fluid is transported between cartilage and bone during loading. Our study examines fluid transport between cartilage and bone from a new perspective using viscoelastic assumptions, in contrast with previous models that used poroelastic models. Further our model incorporates an ellipsoidal fiber distribution for collagen fibers while a previous model used a volume element model. Understanding the velocity and flux of fluid transport between cartilage and bone is key to elucidating the role of transport between cartilage and bone in joint health.