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Thermal stability and structure of cancellous bone mineral from the femoral head of patients with osteoarthritis or osteoporosis

L D Mkukuma¹, C T Imrie², J M S Skakle², D W L Hukins^3,4, R M Aspden¹

¹ Department of Orthopaedic Surgery, University of Aberdeen, Aberdeen AB25 2ZD, UK
² Department of Chemistry, University of Aberdeen, Aberdeen AB25 2ZD, UK
³ Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Aberdeen AB25 2ZD, UK
⁴ Current address: School of Engineering, Mechanical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK

Correspondence to:
Correspondence to:
Professor R M Aspden
University of Aberdeen, Department of Orthopaedic Surgery, Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK; r.aspden{at}abdn.ac.uk

Background: Cancellous bone from patients with osteoarthritis (OA) has been reported to be undermineralised and that from patients with osteoporosis (OP) is more liable to fracture. Changes in the mineral component might be implicated in these processes.

Objectives: To investigate the thermal stability and the mineral structure of cancellous bone from femoral heads of patients with either OA or OP.

Methods: Powdered bone was prepared from femoral heads of patients with either OA or OP and a control group. Composition and thermal stability were determined using a thermogravimetric analyser coupled to a mass spectrometer. Unit cell dimensions and the crystallite size of the mineral were measured using x ray diffraction.

Results: Thermal stability of the bone matrix, or of the mineral phase alone, was little altered by disease, though OA bone contained less mineral than OP or control bone. In all three groups, x ray diffraction showed that the mineral unit cell dimensions and crystallite sizes were the same. The mean carbonate content in the mineral from all three groups was between 7.2 and 7.6% and is suggested to be located in both the A site (that is, substituting for hydroxyl groups), and the B site (that is, substituting for phosphate groups).

Conclusions: These results confirm that there is a lower mass fraction of mineral in OA bone, and indicate that the nature of the mineral is not a factor in either disease process.

Abbreviations: CHA, carbonate hydroxyapatite; MS, mass spectrometry; OA, osteoarthritis; OP, osteoporosis; TGA, thermogravimetric analysis; XRD, x ray diffraction

Keywords: osteoarthritis; osteoporosis; cancellous bone; thermal analysis; x ray diffraction

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