Investigating differences in water content across the tibial cartilage

Abstract

Permeability of the cartilage allows its structure to withstand compressive loads through exudation of water. However, it is not known how the water content varies across the tibial cartilage and whether this varying water content may be related to the need to provide compliance against compressive loading. This study sought to examine the water content across the tibial cartilage and identify regions with low water content and high water content. A porcine tibial plateau was isolated and then analyzed using a MicroCT scanner. Subsequently, the plateau was freeze-dried for 24h and another micro-CT scan was then performed. Tibial cartilage regions were segmented from the micro-CT images taken before and after the freeze-drying process. A Matlab code was developed to obtain the shortest Euclidean distance between cartilage surface and the cartilage-bone interface, and to generate a cartilage thickness map for the tibial plateau. The program was also employed to determine the thickness changes before and after freeze-drying. Medial and lateral cartilage thickness was small (0.4-1.0mm) at the anterior, exterior and posterior menisci-covered regions, and large (1.2-1.8mm) at the interior exposed regions. Decrease in cartilage thickness after freeze-drying was as high as 1.0mm. The decrease was more concentrated towards the anterior regions of the medial and lateral compartments. Substantial decreases in cartilage thickness at the anterior tibial cartilage indicated presence of high water content, which may provide shock absorption against initial compressive loads during walking. © 2010 International Federation for Medical and Biological Engineering.