Subchondral bone histology and grading in osteoarthritis.

Olli-Matti Aho,Petri Lehenkari,Jerome Thevenot,Mikko Finnilä,Simo Saarakkala,Luc Malaval

doi:10.1371/journal.pone.0173726

Olli-Matti Aho, Petri Lehenkari + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0173726

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Journal: PloS one	Publication Date: Mar 20, 2017
Citations: 75	License type: CC BY 4.0

Affiliation: Oulu University Hospital, University of Oulu

Abstract

ObjectiveOsteoarthritis (OA) has often regarded as a disease of articular cartilage only. New evidence has shifted the paradigm towards a system biology approach, where also the surrounding tissue, especially bone is studied more vigorously. However, the histological features of subchondral bone are only poorly characterized in current histological grading scales of OA. The aim of this study is to specifically characterize histological changes occurring in subchondral bone at different stages of OA and propose a simple grading system for them.Design20 patients undergoing total knee replacement surgery were randomly selected for the study and series of osteochondral samples were harvested from the tibial plateaus for histological analysis. Cartilage degeneration was assessed using the standardized OARSI grading system, while a novel four-stage grading system was developed to illustrate the changes in subchondral bone. Subchondral bone histology was further quantitatively analyzed by measuring the thickness of uncalcified and calcified cartilage as well as subchondral bone plate. Furthermore, internal structure of calcified cartilage-bone interface was characterized utilizing local binary patterns (LBP) based method.ResultsThe histological appearance of subchondral bone changed drastically in correlation with the OARSI grading of cartilage degeneration. As the cartilage layer thickness decreases the subchondral plate thickness and disorientation, as measured with LBP, increases. Calcified cartilage thickness was highest in samples with moderate OA.ConclusionThe proposed grading system for subchondral bone has significant relationship with the corresponding OARSI grading for cartilage. Our results suggest that subchondral bone remodeling is a fundamental factor already in early stages of cartilage degeneration.

Highlights

Osteoarthritis (OA) is a progressive joint disorder characterized by the uneven and gradual degeneration of articular cartilage, joint pain, stiffness and loss of function in the absence of chronic autoimmune or autoinflammatory mechanisms [1]
The histological appearance of subchondral bone changed drastically in correlation with the Osteoarthritis Research Society International (OARSI) grading of cartilage degeneration
A more novel, and presumably more consistent [10,11], Osteoarthritis Research Society International (OARSI) grading system focuses on the depth of cartilage degeneration and its extent over the whole joint surface [12]

Summary

Introduction

Osteoarthritis (OA) is a progressive joint disorder characterized by the uneven and gradual degeneration of articular cartilage, joint pain, stiffness and loss of function in the absence of chronic autoimmune or autoinflammatory mechanisms [1]. It is the most common form of arthritis and a significant factor in the public health of industrialized countries [2]. The first widely accepted and adopted histological OA grading system was the Mankin scoring [9] It focuses on architectural changes in articular cartilage and tidemark while attending to cellular changes and proteoglycan content of cartilage [9,10]. OARSI grading system is yet to be systematically compared with the changes in subchondral bone, especially in lower OARSI grades

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