A discrete variant in the third plantar tarsometatarsal joint: Patterns of occurrence in a prehistoric population from west-central Illinois

A small pit in the articular surfaces of the third tarsometatarsal joint has been noted with particularly high frequency in North American Indians. This pit varies in depth, and covers most of the inferior third of the articular surfaces of the third metatarsal and the lateral cuneiform; it is accompanied by remodelling of the inferior surfaces of the bones involved. In the present study, patterns of occurrence are examined in a prehistoric skeletal population from west-central Illinois. This population is extremely well preserved, enabling a thorough examination of feet as well as hands for most individuals. The sample included 496 adults and juveniles above the age of 6 years. Of this total population, 18 per cent exhibit the variation, which occurs more frequently in females and is unrelated to size. Furthermore, 29 per cent of the individuals in which it occurs exhibit this variant only unilaterally, with no significant side differences. Various lesions, trauma and acquired or activity-related aetiologies are explored, as are the patterns of sex association, occurrence near an area of ligamentous attachment and lack of age and size association. It is hypothesized that a discrete genetic trait is represented in the third tarsometatarsal joint of this population in the form of an anomalous interosseous plantar ligament. (C) 1997 by John Wiley & Sons, Ltd.