Mechanobiological Models for Bone Tissue. Applications to Implant Design - Biomechanics of Hard Tissues - page 131

mantle thickness (Figure 4.3). Short-term performance of this kind of implants
has obtained good results, although the long-term performance remains uncertain.
Clinically and numerically, hip resurfacing prostheses resulted in bone resorption
at the superior femoral head and in bone apposition around the stem and at the
stem tip. From the results predicted, the 1 mm cement mantle thickness may be
an appropriate cement configuration.
Most of these examples correspond to the application of phenomenological bone
remodeling models to the study of bone adaptation after prosthesis or fixation
implantation. As commented above, these models are able to predict the long-term
bone response, being an effective tool to evaluate the effect of different design
parameters. However, these models present some limitations. For example, most
of them are not interested in the evaluation of the bone remodeling rate, an effect
that is directly predicted with a mechanistic model. As an example, the mechanistic
bone remodeling model developed by Garcıa-Aznar et al . [20] was used to study
the bone adaptation after THR with an Exeter prosthesis. As shown in Figure 4.4,
the amount and location of bone mass loss are in good agreement with clinical
results [76]. Moreover, these bone changes mainly take place in the first year of
THR in the numerical simulation [20], a result that is very similar to clinical
observations [77].

% Change in
cortical bone density

SDVI
(Ave. Crit. : 75%)
+ 1 . 279e + 00

+ 9 . 500e − 01 Mean % loss

per level

Maximum
quadrant loss

+ 8 . 600e − 01

+ 7 . 700e − 01

+ 6 . 800e − 01

− 24% − 34% (medial)

+ 5 . 900e − 01

+ 5 . 000e − 01

+ 4 . 100e − 01

− 25%

+ 3 . 200e − 01

− 31% (medial)

+ 2 . 300e − 01

+ 1 . 400e − 01

+ 5 . 000e − 01

− 21%

− 25% (posterior)

− 1 . 269e − 01

− 18%

− 20% (post. and lat.)

− 13% − 16% (lateral)

Cemented implant

(a) (b)

Figure 4.4 (a) Bone volume fraction distribution in the
femur after 990 days of prosthesis implantation [20];
(b) change in cortical bone density after THR [76].