Fig. 1.

The 6-point morphotype scoring schemes with examples of each birefringence pattern (‘morphotype’). These images are reproduced from the original study of Martin et al. (1996a). The original scoring scheme from Martin et al. (1996a) is designated with an ‘M’ in the upper left corner of each osteon image. Our modified 6-point scoring scheme, also used in the present study, is designated with an ‘S’ in the lower left corner of each osteon image. The scores in the modified 6-point scheme (S-6-MTS) are as follows: 0 = category N, a dark osteon with no birefringent lamellae; 1 = category OWI, a combination of OI and OW; 2 = category OW, similar to O but the birefringent peripheral ring is weak; 3 = category OI, similar to O but the birefringent peripheral ring is incomplete; 4 = category O osteon with dark interior and strongly birefringent peripheral lamellae; 5 = category D, birefringent lamellae are distributed throughout the wall of the osteon (‘distributed’ osteon group). This group includes ‘bright’ osteons (less frequent) and ‘alternating’ osteons (more frequent). Note that a birefringent peripheral lamella, or ‘ring’, is also called a ‘hoop’.