Motion at the midfoot region during the midtarsal break will be referred to as “dorsiflexion” in this article.
Revisiting the “midtarsal break”†
Article first published online: 11 AUG 2009
Copyright © 2009 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Volume 141, Issue 2, pages 245–258, February 2010
How to Cite
DeSilva, J. M. (2010), Revisiting the “midtarsal break”. Am. J. Phys. Anthropol., 141: 245–258. doi: 10.1002/ajpa.21140
- Issue published online: 5 JAN 2010
- Article first published online: 11 AUG 2009
- Manuscript Accepted: 12 JUN 2009
- Manuscript Received: 31 AUG 2008
- Leakey Foundation
- National Science Foundation. Grant Number: BCS 0751010
- foot evolution;
- hominin locomotion;
- longitudinal arch
The midtarsal break was first described in this journal nearly 75 years ago to explain the ability of non-human primates to lift their heel independently of the rest of the foot. Since the initial description of the midtarsal break, the calcaneocuboid joint has been assumed to be the anatomical source of this motion. Recently, however, it has been suggested that the midtarsal break may occur at the cuboid-metatarsal joint, rather than at the calcaneocuboid joint. Data compiled from X-rays, dissections, manual manipulation of living primate feet, video of captive catarrhines, and osteological specimens concur that the midtarsal break is a complex motion caused by dorsiflexion at both joints with the cuboid-metatarsal joint contributing roughly 2/3 of total midfoot dorsiflexion, and the calcaneocuboid joint only about 1/3 of total midfoot dorsiflexion. The convexity of the proximal articular surface of the fourth and fifth metatarsals and corresponding concave cuboid facets provide skeletal correlates for the presence of midfoot dorsiflexion at the cuboid-metatarsal joint. Study of hominin metatarsals from Australopithecus afarensis, A. africanus, Homo erectus, and the metatarsals and a cuboid from the OH 8 foot show little capacity for dorsiflexion at the cuboid-metatarsal joint. These results suggest that hominins may have already evolved a stable midfoot region well adapted for the push-off phase of bipedalism by at least 3.2 million years ago. These data illuminate the evolution of the longitudinal arch and show further evidence of constraints on the arboreal capacity in early hominins. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc.