Abstract
Background: The Evans osteotomy has been proven to be very effective in treating flatfoot deformity in adults. However, it has not been shown whether the site of osteotomy influences the contact areas and peak pressures within the subtalar joint. It is hypothesized that the posterior facet of the calcaneus rotates posteriorly and laterally resulting in altered contact characteristics and peak pressures in the subtalar joint.
Materiala and Methods: We used a finite-element model (FEA) of the hindfoot. Computed tomography slides of patients who suffered from adult flatfoot deformity were prepared by means of open-source software and converted into a three-dimensional model of the hindfoot. The FEA model allows the virtual performance of an osteoteomy and simulates force transmissions through the hindfoot and calculates joint contact characteristics and peak pressure alterations as well. Two different kind of osteotomies were tested:
-
an osteotomy 10mm proximal to the calcaneocuboid joint line and
-
an osteotomy performed adjacent to the posterior calcaneal facet.
Results: There were small but significant differences found between osteotomies done either close to the calcaneocuboid joint or directly adjacent to the posterior facet. At both sites the posterior calcaneal facet rotated posteriorly and laterally. However we found a significant decreases in contact areas and raises in peak pressures within the subtalar joint in cases where the osteotomy was performed close to the posterior calcaneal facet.
Summary: This study presents the effects of virtual Evans osteotomies on the subtalar joint and their dependence upon the site of the osteotomies.
Correspondence should be addressed to: D. Singh, BOFAS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
