Fractures of the talar neck. A mechanical study of fixation

Anatomical reduction and rigid internal fixation of fractures of the talar neck allow early mobilization of the ankle and subtalar joints. Forty fresh tali from cadavera were fractured across the talar neck and were internally fixed with one of four methods. The specimens were again loaded to failure, and mean yield loads, yield deformations, stiffness, and energy absorbed were compared. The two configurations of screws that were inserted posterior to anterior provided yield loads superior to those of screws inserted anterior to posterior. All combinations of screws were stronger than Kirschner wires. Comparisons of yield deformations, stiffness, and energy absorbed corroborated these results. The calculated theoretical maximum shear force across the talar neck during active motion was 1129 newtons. This exceeded the strength that was provided by Kirschner wires and anteriorly inserted screws but not that provided by screws that were placed posteriorly.