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

Figure 2 - Predominant material orientations and density distribution for a coronal (a), transverse (b) and
sagittal (c) slices of the proximal femur and sagital (d) slice of the medial condyle.
Figure 2 shows the predominant material orientations for each element associated with
the highest magnitude of directional Young’s Modulus. The length and shade is
proportional to the density values for each element calculated using a power correlation
with the mean Young’s Modulus [20]. The areas where medium or high density values
can be found for the proximal femur are the great trochanter, along the lateral epiphysis,
towards the articular surface of the femoral head, the inferior side of the femoral neck,
lesser trochanter, the calcar femorale and along the surface of the diaphysis (cortical
region of the femoral shaft) [21, 22]. These are areas of high compression or tension
stresses due to bending of the proximal femur because of the application of the hip
contact force and the action of the attached muscle groups [1, 23]. The lower value
regions observed included the Ward’s triangle, Babcock’s triangle and the
intermedullary canal, regions known for being either composed of thin and loosely
arranged trabeculae, or where virtually no trabecular bone can be found [24]. The main
documented trabecular groups are also clearly represented [24]. These arise as a
structural response to the necessity to transfer load along the femur from an oblique to
vertical direction [21]. Finally, the perpendicular arrangement of trabeculae along the
articulate surface of the condyles is clearly present as response to the compression
caused by the weight bearing function of the femur and its rotary movement. The high
density distribution around the epiphyseal line is a result of the thicker and coarser
trabeculae that can be found in this region; in contrast, finer and denser trabeculae were
also observed towards the metaphysis. Lastly, the trabeculae radiating from the
intercondylar notch towards both condyles were also predicted [25].