Functional Adaptation of the Calcaneus in Historical Foot Binding

Abstract

The normal structure of human feet is optimized for shock dampening during walking and running. Foot binding was a historical practice in China aimed at restricting the growth of female feet for aesthetic reasons. In a bound foot the shock-dampening function normally facilitated by the foot arches is withdrawn, resulting in the foot functioning as a rigid extension of the lower leg. An interesting question inspiring this study regards the nature of adaptation of the heel bone to this nonphysiological function using the parameters of cancellous bone anisotropy and 3D fabric topology and a novel intertrabecular angle (ITA) analysis. We found that the trabecular microarchitecture of the normal heel bone, but not of the bound foot, adapts to function by increased anisotropy and preferred orientation of trabeculae. The anisotropic texture in the normal heel bone consistently follows the physiological stress trajectories. However, in the bound foot heel bone the characteristic anisotropy pattern fails to develop, reflecting the lack of a normal biomechanical input. Moreover, the basic topological blueprint of cancellous bone investigated by the ITA method is nearly invariant in both normal and bound foot. These findings suggest that the anisotropic cancellous bone texture is an acquired characteristic that reflects recurrent loading conditions; conversely, an inadequate biomechanical input precludes the formation of anisotropic texture. This opens a long-sought-after possibility to reconstruct bone function from its form. The conserved topological parameters characterize the generic 3D fabric of cancellous bone, which is to a large extent independent of its adaptation to recurrent loading and perhaps determines the mechanical competence of trabecular bone regardless of its functional adaptation.

3D Architecture of Trabecular Bone in the Pig Mandible and Femur: Inter-Trabecular Angle Distributions

“…Here, we show that the node abundances, the angular distributions, and mean ITA values in three different parts of the pig mandible and the pig proximal femur are principally similar to other previously analyzed bone samples [of the human proximal femur (Reznikov et al, 2016) and two differently loaded groups of human calcanei (Reznikov et al, 2017) in terms of node type proportions and the maximal angular offset of connected elements]. These results, therefore, clearly show that ITA values are conserved even between species from different mammalian taxonomic groups and between bones that carry out different mechanical functions.…”

“…The prevalence of nodes with low connectedness and the mean ITA values typical of the maximal angular offset possibly indicate a compromise between minimizing of metabolic cost (or achieving sufficient shock dissipation) and maximizing sufficient network stability in multidirectional loading of trabecular bone tissue (Deshpande et al, 2001). Reznikov et al (2017) have applied the ITA analysis approach to the study of functional adaptation of trabecular bone in the human calcaneus by comparing normal feet and museum specimens of feet subjected to foot binding (historical cultural practice of foot deformation). They found that while the anisotropy pattern in the calcaneus closely reflects the pattern of loading and follows the tensile and compressive force vectors, the aforementioned ITA parameters in the calcanei of the two groups were nearly identical.…”

Foot binding in a Ming dynasty cemetery near Xi’an, China

“…Explicit descriptions of foot binding became available beginning in the 19 th century, when anti-foot binding crusaders, including both Chinese people and foreigners such as missionaries, set about photographing and documenting the phenomenon. Titillating souvenirs such as bound-foot women's shoes, photographs of prostitutes exposing their bound feet, and even, disturbingly, preserved feet themselves were brought back to the West by sailors and other travelers and became part of museum collections (Reznikov et al, 2017). In the 20 th century, first-hand accounts by footbound women themselves were also published (Levy, 1992).…”

“…• the calcaneus tends to have a more vertical orientation than in unbound feet (Howard and Pillinger, 2010;Reznikov et al, 2017;Richardson, 2009); • all or most foot bones are reduced in size, some with dramatically altered morphology, especially the metatarsal bones and phalanges of rays 2 through 5 Guo, 2011;Howard and Pillinger, 2010); • arthropathies throughout the foot and ankle, and changes in the angles of articulations, are common (Guo, 2011;Ma et al, 2013); • the pattern of weight bearing in the feet is shifted, with the heel bearing more weight and the toes no longer functioning in their normal capacity during standing or walking Qin et al, 2015;Reischl et al, 2008;Reznikov et al, 2017); • the ankle has less motion in the sagittal plane Zhang et al, 2015); • bone density is reduced in the foot, and some studies have found that bone density is reduced in other weight bearing parts of the skeleton as well, while other studies have not found this to be the case; the discrepancy is possibly due to lifelong differences in physical activity among groups of footbound women (Cummings et al, 1997;Guo, 2011;Howard and Pillinger, 2010;Pan et al, 2013;Qin et al, 2015;Richardson, 2009); • development of anisotropic microarchitecture of trabecular bone in the calcaneus is somewhat disrupted (Reznikov et al, 2017); • and elderly women with bound feet experience falls that result in fractures more often than women without bound feet do, though working class rural women seem to have been somewhat protected from this effect by remaining active all their lives (Cummings et al, 1997;Qin et al, 2015;Richardson, 2009).…”

Cartilage Stiffness Effect on Foot Biomechanics of Chinese Bound Foot: A Finite Element Analysis

“…The change of strain in the fourth ray showed to be relatively noticeable with a gradual decrease as the Young’s modulus of cartilage increased from the reference value to 15-fold. In a study evaluating the calcaneus functional adaptation in foot binding, the mechanical influence of plantar fascia was even disregarded ( Reznikov et al, 2017 ).…”