ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

Figure 4: Mean error in orthotropy assumption at different locations in the femoral head,
where A is anterior, C is central, P is posterior, S is superior and I is inferior regions. Plotted
values have also been colour coded for clarity – blue is lowest and red is highest.
6. DISCUSSION
The range of Young’s moduli found is consistent with the literature [22]. Stiffer bone
appears to lie in the centre of the femoral head, which may coincide with the main
direction of trabeculae. This is consistent with the data presented in Banse et al. [28].
The high error in the orthotropic assumption indicates that the bone in the femoral head
is not strictly orthotropic.
Li and Aspden [2] found data to support a decrease in stiffness in OP bone due to
reduced bone mass, and an increase in stiffness in OA bone due to increased production
of defective bone. This is supported by the reduction of porosity and increase in strength
found in OA samples when compared with OP samples.
8. REFERENCES
1. Sun, S.S.; Ma, H.L.; Liu, C.L.; Huang, C.H.; Cheng, C.K. & Wei, H.W. (2008), 'Difference in femoral head
and neck properties between osteoarthritis and osteoporosis', Clinical Biomechanics 23, S39-S47.
2. Li, B. & Aspden, R. M. (1997), 'Composition and Mechanical Properties of Cancellous Bone from the
Femoral Head of Patients with Osteoporosis or Osteoarthritis', Journal of Bone and Mineral Research 12(4),
641-651.
3. Cummings, S. R. & Melton, L. J. (2002), 'Epidemiology and outcomes of osteoporotic fractures', The Lancet
359, 1761-1767.
4.Gullberg, B.; Johnell, O. & Kanis, J. A. (1997), 'World-wide Projections for Hip Fracture', Osteoporosis
International 7, 407-413.
5. Avakian, Z.; Shiraev, T.; Lam, L. & Hope, N. (2011), 'Dynamic hip screws versus proximal femoral nails for
intertrochanteric fractures', ANZ Journal of Surgery 82, 56-59.
6. Parker, M. J. (1992), 'Cutting-out of the dynamic hip screw related to its position', The Journal of Bone and
Joint Surgery. British volume 74(4), 625.
7. Haynes, R. C.; Poll, R. G.; Miles, A. W. & Weston, R. B. (1997), 'Failure of femoral head fixation: a
cadaveric analysis of lag screw cut-out with the gamma locking nail and AO dynamic hip screw', Injury 29(7),
337-41.