Calcaneal varus angle change in normal calcaneus: a three-dimensional finite element analysis

The objective of the study was to investigate the stress changes in the posterior articular surface of the calcaneus following alternation of the calcaneal varus angle in normal calcaneus and discuss the clinical significance of the calcaneal varus angle. Axial view radiographs of 165 volunteers were obtained to measure the calcaneal varus angle of normal calcaneus. A calcaneal model with different varus angle changes (including +2A degrees, +4A degrees, +6A degrees, -2A degrees, -4A degrees, and -6A degrees) was established using Creo 2.0 software. Stress changes at different calcaneal varus angles in the posterior articular surface of the calcaneus under a load of 100 N were measured. Stressed areas in posterior articular facets were slightly fewer following +2A degrees, +4A degrees, and +6A degrees changes in varus angle than in normal varus angles with stress concentering regions moving to the anteromedial aspect of the posterior calcaneal facet. However, stress concentering areas in posterior calcaneal facets following -4A degrees and -6A degrees changes in varus angle obviously moved to the anterior and posterior medial side of posterior calcaneal facets. Stress distribution in the posterior articular surface of the calcaneus varies with the calcaneal varus angle. The decrease in calcaneal varus angle following operative treatment of calcaneal fractures should be controlled within 2A degrees.