Objective: 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.
Methods: Eight specimens were dissected and the calcaneus was removed. The measurements were taken from portions of the subtalar joint.
Results: 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.
Conclusion: 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.