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Title: Mechanical factors influencing impaction bone grafting
Author: Mak, Siu Yan
ISNI:       0000 0001 3617 1328
Awarding Body: University of Bath
Current Institution: University of Bath
Date of Award: 2007
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Impaction grafting for bone stock loss in revision total hip arthroI;>lasty has been used for over a decade. This technique typically involves the insertion of a cemented highly polished stem into impacted morsellised allograft bone. The aim is to compensate for the bone stock loss after failed primary hip arthroplasty and to provide a mechanical and biological scaffold for mechanical support and bone remodelling. The primary objective of this study is to quantify and optimise the graft properties so as to provide maximum supportive forces to the stem, and, at' the same time, to minimise the amount of per.:operative and post-operative femoral fractures. More than 60 parameters that could affect the mechanical properties of graft have been identified. Porcine bone from femoral heads was used in the study which was primarily divided into two parts: fundamental studies of the graft material, and in-vitro mechanical testing to replicate the clinical application of impaction bone grafting. Various techniques of graft preparation including defatting of the graft were investigated. A die-plunger was employed to perform uni-axial compressive testing on the graft at varying strain rates. It was found that defatted' graft demonstrated higher stiffness. Higher rates of loading resulted in increases in stiffness, hoop strain, axial force and Poisson's ratio. Preloading of the graft provided more predictable mechanical characteristics. Cyclic compressive testing showed th~t individual graft particles fractured during compression. In addition, it was found that the graft demonstrated increased viscoelastic properties at higher strain rates. In-vitro mechanical testing was also performed to compare the level of mechanical stability of a cemented polished stem with a larger uncemented polished stem. Composite femora were '' used for this comparison. It was found that the cemented stem showed higher mechanical stability in terms of the level of micromotion and migration, and uncemented stem failed in a catastrophic manner. The study provided information on how various factors contributed to the mechanical behaviour of bone graft and identified parameters that should be used when in-vitro testing of bone graft materials for use in impaction grafting.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available