A numerical study to determine pericellular matrix modulus and evaluate its effects on the micromechanical environment of chondrocytes.

Chondrocyte biosynthesis is highly sensitive to mechanical strain. A thin pericellular matrix (PCM) surrounds the cell and plays an important role in mechanotransduction. PCM material properties are difficult to measure directly because of its size and connectivity to both cell and extracellular matrix (ECM). The purpose of this study was to develop a method of calculating linear elastic properties of the PCM using an inverse finite element approach with experimental properties of cell and chondron taken from the literature. Finite element models were constructed of both the equivalent chondron case and the chondrocyte-PCM structure, and a Fibonacci search obtained PCM moduli that matched the ECM strain field between the two cases. The most important result was that ECM strain adjacent to a chondron inclusion was sensitive to the chondron properties and may be used to calculate PCM mechanical properties, consistent with our strain field hypotheses. PCM moduli obtained through this method range from 43 to 240 kPa, were significantly higher than previously published but resulted in only a 0.5-21% decrease in relative effective cell strain. Similarities between effective strain ratios led to the conclusion that matching experimental techniques used to measure cell and PCM properties was more important than absolute values of the properties.