Department of Anthropology, University of Texas at Austin
March 26, 2015 1:45, Grand Ballroom E/F/G
In humans, the posterior margin of the distal tibia articular surface has a greater inferior projection than the anterior margin, creating an anteriorly-inclined ankle joint in the sagittal plane (“tibial arch angle”, TAA). Previous work found a significant relationship between the TAA and radiographic measures of arch height, and proposed that an anteriorly-inclined ankle joint is a developmental by-product of longitudinal arch development in humans (DeSilva & Throckmorton 2010). Currently, however, our understanding of the TAA and how it relates to the arch is limited.
This study further tests the relationship between the TAA and the longitudinal arch. First, a sample of adult foot and ankle x-rays (N=120) was used to investigate the relationship between the TAA and arch height. Second, ontogenetic changes in TAA morphology were catalogued in juvenile skeletal remains from two archaeological populations to test whether the anterior inclination of this joint develops concurrently with the arch. OLS-regression of TAA on a clinical measure of arch height reveals that variation in the TAA explains less than 1% of the variance in arch height for the adult radiographic sample (r2=0.0089, p=0.344). For the ontogenetic sample, individuals in the age range spanning arch development (0-6 years) had lower, but not significantly different, TAA values than older individuals, suggesting that the anterior inclination of the joint is not a by-product of arch development. These results question the link between the TAA and longitudinal arch height, and also whether this trait should be used to reconstruct arch height in fossil hominins.
Funded by The Leakey Foundation and NSF Doctoral Dissertation Research Improvement Grant #BCS-1409530