High prevalence of tarsal coalitions and tarsal joint variants in a recent cadaver sample and its possible significance

Tarsal coalitions (TC) are defined as fibrous (beyond normal ligaments), cartilaginous, or osseous unions of at least two tarsal bones. Most of the clinical studies report the prevalence of TC as <1%, but they disregard the asymptomatic coalitions. Because TC have been associated with pathologic conditions, including degenerative arthritic changes, knowledge of their prevalence has clinical importance. The aim of our study was to establish the prevalence of TC and tarsal joint variants. A total of 114 feet from 62 cadavers (average age = 78 years) without obvious foot pathologies were dissected at the Department of Anatomical Sciences, The University of Adelaide. Ten non-osseous TC in eight subjects were identified: two talocalcaneal and eight calcaneonavicular (occurred twice bilaterally). Variant calcaneonavicular and cuboideonavicular joints were found in 8% and 31% of feet, respectively. Other joint variants included a variable number of talocalcaneal joint surfaces and sesamoid bones. No secondary TC (due to trauma, infections, or neoplasm) were found. Our study demonstrated that the overall prevalence of TC is higher (13%) than previously thought; tarsal joint variations (39%) and sesamoid bones (42%) were common as well. The supposed secular increase in the prevalence of TC as well as the high number of anatomical variants could reflect a short-term response to altered life-style or a microevolutionary trend due to relaxed selection.