Biomechanical study comparing 3 types of internal fixation of the Duparc grade IV fracture of the calcaneum: superiority of triangular internal fixation

Purpose of the study We present an in vitro biomechanical study performed t o evaluate and compare, for an experimentally produced fracture of the calc aneum (Duparc grade IV), the reaction of 3 standard models of internal fixa tion commonly used in these fractures and which occupy different volumes. Materials and methods We compared different methods of fixation using fresh human calcanei. In two experimental series, we compared triangular interna l fixation (3 1/4 tube AO plates Saragaglia), Y internal fixation (2 1/3 tu be AO plates Bezes), isolated screw technique (three 3.5 diameter screws, t wo 4.5 diameter screws). The plates and screws were made of identical mater ial (316L). Both series used 8 pairs of bone (talocalcaneum system) with th e same fracture submitted to a 200N to 1000N load. Stiffness and movement w ere analyzed using 8 references on the calcaneum. Results The stiffness and movement analysis with 8 references points demons trated the superior resistance to bending with the triangular internal fixa tion. Fixation stability was significantly better than with the Y or screw technique. Discussion This study underlined the importance of triangular trabecular or ganization of cancellous bone on calcaneum biomechanics. We showed that the 3 (anterior, posterior and inferior) trabeculae must be repaired in calcan eum fractures to achieve horizontal and vertical stability of the talar joi nt. Conclusion In our hands, restoration of the triangular architecture of calc aneum fractures, to resemble a roof truss, where the talus is fixed to the triangle vertex, is fundamental to obtain a rigid and stable internal fixat ion.