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Mechanical properties of cancellous bone from the acetabulum in relation to acetabular shell fixation and compared with the corresponding femoral head

Lookup NU author(s): James Holland, Professor David Deehan


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© 2018 IPEM. To gain initial stability for cementless fixation the acetabular components of a total hip replacement are press-fit into the acetabulum. Uneven stiffness of the acetabular bone will result in irregular deformation of the shell which may hinder insertion of the liner or lead to premature loosening. To investigate this, we removed bone cores from the ilium, ischium and pubis within each acetabulum and from selected sites in corresponding femoral heads from four cadavers for mechanical testing in unconfined compression. From a stress-relaxation test over 300 s, the residual stress, its percentage of the initial stress and the stress half-life were calculated. Maximum modulus, yield stress and energy to yield (resilience) were calculated from a load-displacement test. Acetabular bone had a modulus about 10-20%, yield stress about 25% and resilience about 40% of the values for the femoral head. The stress half-life was typically between 2-4 s and the residual stress was about 60% of peak stress in both acetabulum and femur. Pubic bone was mechanically the poorest. These results may explain uneven deformation of press-fit acetabular shells as they are inserted. The measured half-life of stress-relaxation indicates that waiting a few minutes between insertion of the shell and the liner may allow seating of a poorly congruent liner.

Publication metadata

Author(s): van Ladesteijn R, Leslie H, Manning WA, Holland JP, Deehan DJ, Pandorf T, Aspden RM

Publication type: Article

Publication status: Published

Journal: Medical Engineering and Physics

Year: 2018

Volume: 53

Pages: 75-81

Print publication date: 01/03/2018

Online publication date: 01/02/2018

Acceptance date: 15/01/2018

ISSN (print): 1350-4533

ISSN (electronic): 1873-4030

Publisher: Elsevier Ltd


DOI: 10.1016/j.medengphy.2018.01.005


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