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In vivo and mechanical evaluation of Calcium Polyphosphate for bone regeneration in revision total hip replacements Comeau, Patricia Ann

Abstract

Revision total hip replacements (THRs) commonly involve the cementing of a femoral component into a compressed bone graft such as morsellized cancellous allograft in order to encourage restoration of the living bone stock that has been lost in a primary THR. However, current problems associated with allograft include risk of disease transmission, limited availability, reproducibility, and cost. To address these issues synthetic scaffolds have been proposed as a substitute material due to their availability and ease of preparation and sterilization. Calcium polyphosphate (CPP) is one novel synthetic scaffold that has shown good mechanical properties and biocompatibility, and is evaluated biologically and mechanically in this study. The in vivo study observed how marrow stromal cell (MSC) proliferation and differentiation was affected by the substrate material. Here CPP, morsellized cancellous bone (MB), and hydroxyapatite/tricalcium phosphate (HA/TCP) were seeded with MSCs and implanted subcutaneously under the back skin of NOD/Scid mice. At 0, 7, 14, and 28 days the samples were harvested and the proliferation characteristics and gene expression were analyzed. CPP, HA/TCP and MB were all shown to have similar proliferation characteristics and gene expression. In the mechanical study CPP was combined with PLA to form particulate composites and with PMMA to form solid composites. These composites were then tested in un-compacted and pre-compacted states in confined compression. The results show that the solid composites had the greatest improvement over MB in terms of construct stiffness, with the particulate composites having the next greatest improvement when pre-compacted. The study confirmed that CPP has potential as a synthetic scaffold for replacing MB in the revision THR procedure.

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