Biomedical Engineering – From Theory to Applications

Orthopaedic Modular Implants Based on Shape Memory Alloys
c. The average values considered for the longitudinal modulus of elasticity, E, are: 18.500
N/mm 2 for the compact bone, situated in the exterior zone of the bone and 2 N/mm 2
for the spongy bone, situated in the interior zone. The value of the Poisson coefficient
was 0.3.
d. The virtual central canal is realized in accordance with the obtained tomographies, so
the complex spatial structure is ensured.
Ulna: The ulna is a long bone of the forearm, broader proximally, and narrower distally.
Proximally, the ulna has a bony process, the olecranon process, a hook-like structure that fits
into the olecranon fossa of the humerus. This prevents hyperextension and forms a hinge
joint with the trochlea of the humerus (Gray, 2000). There is also a radial notch for the head
of the radius, and the ulnar tuberosity to which muscles can attach. Distally (near the hand),
there is a styloid process. The long, narrow medullary cavity is enclosed in a strong wall of
compact tissue which is thickest along the interosseous border and dorsal surface. At the
extremities the compact layer thins. The compact layer is continued onto the back of the
olecranon as a plate of close spongy bone with lamellae parallel. The sections of ulna bone
realized in SolidWorks are presented in Figure 4b. Finally, it is obtained the virtual model
of the ulna bone (Figure 4c).
a) b) c)
Fig. 4. Ulna bone (a) (Gray,2000), sections of ulna bone (b), the virtual model of ulna bone (c)
a) b) c)
Fig. 5. The loading forces (a) and the resulted stress maps (b and c) for the first case
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