A comparison of plates with and without locking screws in a calcaneal fracture model.

BACKGROUND We compared different plates in an experimental calcaneal fracture model under biocompatible loading. METHODS Four plates were tested: a plate without locked screws (Synthes), and three different plates with locked screws (Newdeal, Darco, Synthes). Synthetic calcanei (Sawbone) were osteotomized to create a fracture model, and the plates were fixed onto them. Seven specimens for each plate model were subjected to cyclic loading (preload 20 N, 1,000 cycles with 800 N, 0.75 mm/s), and load to failure (0.75 mm/s). Motion, forces, plastic deformation of the plate, and consequent depression of the posterior joint facet were analyzed. RESULTS During cyclic loading, all plates with locked screws showed statistically significant lower displacement in the primary loading direction than the plates without locked screws. Mean values (mm) of maximal displacements for each plate during cyclic loading were as follows: Synthes, 3.5; Darco, 4.5; Newdeal, 5.0; Synthes without locked screws, 7.5; (p < 0.001). No statistically significant differences between the plates were found in relation to loads to failure and corresponding displacement. CONCLUSION This is the first biomechanical study to assess the stability of different plates currently in use in our practice for the fixation of calcaneal fractures. Our results showed that plates with locked screws provided greater stability during cyclic loading than the plate without locked screws.