Subchondral bone microarchitecture and mineral density in human osteoarthritis and osteoporosis: A regional and compartmental analysis.

Yunfei Li,Niall Sullivan,Haroon Ahmed,Ashley Blom,Enrico Dall'Ara,Yulia Liem,Mohammed Sharif

doi:10.1002/jor.25018

Abstract

Osteoarthritis (OA) and osteoporosis (OP) are historically considered to be inversely correlated but there may be an overlap between the pathophysiology of the two diseases. This study aimed to investigate the subchondral bone microarchitecture and matrix mineralization, and the association between them in OA and OP in relation to the degree of cartilage degeneration. Fifty-six osteochondral plugs were collected from 16 OA femoral heads. They were graded on a regional basis according to the stages of cartilage degeneration, as evaluated by a new macroscopic and a modified microscopic grading system. Twenty-one plugs were collected from seven femoral heads with OP. Plugs were scanned by microcomputed tomography and the microarchitectural and mineral properties were obtained for both subchondral plate and trabecular bone. Microarchitecture and material and apparent densities of subchondral bone in OP were similar to regions with early cartilage degeneration but different from regions with advanced cartilage degradation in OA femoral heads. Subchondral trabecular bone was more mineralized than subchondral plate in both OP and OA, and this compartmental difference varied by severity of cartilage degradation. Furthermore, the relationship among trabecular bone volume fraction, tissue mineral density, and apparent bone density was similar in OP and different stages of OA. Subchondral bone microarchitecture and mineral properties in OP are different from OA in a regionalized manner in relation to stages of cartilage degeneration. Both regional and compartmental differences at structural, material, and cellular levels need to be studied to understand the transition of OA subchondral bone from being osteoporotic to sclerotic.

Highlights

Osteoarthritis (OA) and osteoporosis (OP) are two of the most common skeletal diseases in the ageing population.[1]
We used a combined macroscopic and microscopic sampling procedure which permitted a better representation of the regional difference in subchondral bone microarchitecture and matrix mineralization in relation to the severity of cartilage degeneration
We showed that subchondral bone properties in OP was similar to regions with early but different from regions with advanced cartilage degeneration in OA

Summary

| INTRODUCTION

Osteoarthritis (OA) and osteoporosis (OP) are two of the most common skeletal diseases in the ageing population.[1]. OA and OP are thought to be inversely related as they rarely occur in the same patient,[16] and the presence of OA is generally associated with higher systemic bone mineral density.[1] One hypothesis is that more compliant subchondral support due to bone loss in OP protects the overlying cartilage.[14,15,17,18,19] the fact that increased remodeling and bone loss are present in OA, as mentioned above, suggests a possible overlap between the pathophysiology of the two diseases.[20] This overlap provides the rationale for the use of bone‐targeting agents as a potential disease modifying OA drugs (DMOADs).[20] But, various established anti‐ resorptive OP drugs, such as bisphosphonates and estrogen, have failed to show solid clinical evidence of efficacy for OA.[21] These paradoxes point to a more complicated situation when studying the relationship between bone remodeling in OA and OP. The purpose of this study was to investigate the differences in subchondral bone between OP and OA by comparing the microarchitecture, mineralization, and the correlation between microarchitecture and mineralization in a regionalized and compartmentalized manner, using a coupled macroscopic and microscopic sampling procedure

| MATERIALS AND METHODS

| RESULTS

Findings

| DISCUSSION