Elastic, Dynamic Viscoelastic and Model-Derived Fibril-Reinforced Poroelastic Mechanical Properties of Normal and Osteoarthritic Human Femoral Condyle Cartilage

Mohammadhossein Ebrahimi,Mikko A J Finnilä,Aleksandra Turkiewicz,Martin Englund,Petri Tanska,Rami K Korhonen,Simo Saarakkala

doi:10.1007/s10439-021-02838-4

Mohammadhossein Ebrahimi, Mikko A J Finnilä + Show 5 more

Open Access

https://doi.org/10.1007/s10439-021-02838-4

Copy DOI

Abstract

Osteoarthritis (OA) degrades articular cartilage and weakens its function. Modern fibril-reinforced poroelastic (FRPE) computational models can distinguish the mechanical properties of main cartilage constituents, namely collagen, proteoglycans, and fluid, thus, they can precisely characterize the complex mechanical behavior of the tissue. However, these properties are not known for human femoral condyle cartilage. Therefore, we aimed to characterize them from human subjects undergoing knee replacement and from deceased donors without known OA. Multi-step stress-relaxation measurements coupled with sample-specific finite element analyses were conducted to obtain the FRPE material properties. Samples were graded using OARSI scoring to determine the severity of histopathological cartilage degradation. The results suggest that alterations in the FRPE properties are not evident in the moderate stages of cartilage degradation (OARSI 2-3) as compared with normal tissue (OARSI 0-1). Drastic deterioration of the FRPE properties was observed in severely degraded cartilage (OARSI 4). We also found that the FRPE properties of femoral condyle cartilage related to the collagen network (initial fibril-network modulus) and proteoglycan matrix (non-fibrillar matrix modulus) were greater compared to tibial and patellar cartilage in OA. These findings may inform cartilage tissue-engineering efforts and help to improve the accuracy of cartilage representations in computational knee joint models.

Highlights

Mechanical properties of articular cartilage play a vital role in the knee by enabling the proper function of the joint
Those properties originate from the multiphasic heterogeneous structure of the extracellular matrix, which comprises of interstitial fluid, collagen fibrils, and negatively charged proteoglycans (PGs)
We hypothesized based on our earlier findings in patellar and tibial human cartilage[9,39] that PG matrix- and collagen fibril network-related fibril-reinforced poroelastic (FRPE) properties are weakened in femoral condyle cartilage at the moderate stages of OA, while the tissue permeability remains unchanged until late OA

Summary

Introduction

Mechanical properties of articular cartilage play a vital role in the knee by enabling the proper function of the joint Those properties originate from the multiphasic heterogeneous structure of the extracellular matrix, which comprises of interstitial fluid, collagen fibrils, and negatively charged proteoglycans (PGs). The PG loss is progressive and that reduces the cartilage load-bearing capacity in equilibrium.[23] Either at the same time or subsequently, the collagen network fibrillates, and part of the tissue-swelling related pretension of the fibrils is lost.

Objectives

Methods

Results

Discussion

Conclusion