Bone Implant Design Using Optimization Methods - Biomechanics of Hard Tissues - page 286

Bone mass variation.

Table 10.9

( β d , β t , β r ) Totally coated Half coated

Zone P (%) Zone PC (%) Zone E (%) Zone P (%) Zone PC (%) Zone E (%)

(1,0,0) − 23.32 − 29.57 − 56.48 − 18.48 − 26.25 − 54.61

(0,1,0) − 21.44 − 33.98 − 61.92 − 18.67 − 32.36 − 62.31

(0,0,1) − 5.55 − 21.20 − 55.94 + 10.43 + 2.76 − 50.16

− − − − − −

(1/3,1/3,1/3) 14.72 24.72 54.62 12.15 23.49 53.31

(0.6,0.2,0.2) − 20.03 − 27.57 − 55.16 − 16.74 − 27.01 − 55.12

(0.2,0.6,0.2) − 18.46 − 26.90 − 56.51 − 14.04 − 26.38 − 54.96

(0.2,0.2,0.6) − 9.78 − 19.06 − 51.77 − 9.97 − 21.53 − 52.69

Initial shape − 14.24 − 24.87 − 58.20 − 14.01 − 24.75 − 58.09

Table 10.9 presents the bone loss variation in proximal and exterior femoral
regions defined in Figure 10.18. The percentage variation is referred to as the
total amount of bone immediately after the surgery and the minus sign means
loss of mass. In this case, half coated stems have less bone resorption than
totally coated ones. In fact, the lack of porous coating in the distal part implies a
proximal fixation, which is useful to minimize the bone resorption. Nevertheless,
for all nondominated points and both coating lengths, a smaller amount of
bone resorption is achieved in the exterior region (zone E) compared to the
initial shape. In zones P and PC, nondominated solutions with high weight for the
remodeling function ( β r ) also presents less bone resorption than initial geometry. In

Figure 10.19 some examples of long-term bone density distribution are presented,

Zone PC Zone E

Zone P

Femur

Figure 10.18 Definition of the zones to compare bone remodeling results.