Page 252 - Advances in Biomechanics and Tissue Regeneration

248 12. BIOMECHANICAL STUDY IN THE CALCANEUS BONE AFTER AN AUTOLOGOUS BONE HARVEST

(A) (B)

(C) (D)

(E) (F)
FIG. 12.6 Minimum principal stress in an intact foot with loads of 150 (A), 300 (C), and 375 N (E), respectively, on the Achilles tendon and with
7.5mm bone excision and loads of 150N (B), 300N (D), and 375 N (F), respectively, on the Achilles tendon.

related both to bone strength and load transmission. However, the bone distribution is not homogenous. An area of
sparse (or absent) mineralization exists in the anterior portion of the calcaneus. This region is termed the “neutral
triangle” or Ward’s triangle [22, 23]. One study measured the cortical thickness of these internal calcaneal trabecular
arrays in 14 dry, frozen specimens [23]. Those results concluded that the primary and secondary fracture lines, those
often associated with calcaneus fractures, correlated with the trabecular patterns and often initiating in the neutral
triangle [23]. Regions lacking trabeculae, or parallel to organized trabeculae, were the weakest plane of stress
resistance.
In the current study, compressive and tensile stress was redistributed to the borders of the site of graft harvest.
Additionally, the posterior aspect of the calcaneus was a source of stress during loaded conditions. In instances of
maximum bone extraction, greater stress values were recorded compared with the intact foot. Furthermore, we noted

I. BIOMECHANICS