Determining the angle of screw placement for internal fixation of calcaneal fractures.

Abstract

This study was designed to determine the angle off the perpendicular to the lateral calcaneal wall at which a screw would need to be angled to avoid entering the subtalar joint medially. It also determined the distance inferior to the articular surface at which a screw would need to be placed to avoid that penetration if the screw was placed perpendicular to the lateral calcaneal wall. Eight specimens were dissected and the calcaneus was removed. The measurements were taken from portions of the subtalar joint. To avoid medial penetration, a screw at the anterior portion of the posterior facet would need to be angled 5 degrees plantar medially or placed 1.5 millimeters below the edge of the articular surface. In the midportion, placements are 20 degrees or 10 millimeters; posteriorly, placements are 32 degrees or 15 millimeters. This study shows that using a lateral approach, it is possible to position internal fixation screws without disrupting the articular surfaces of the medial subtalar joint.