OBJECTIVE: To evaluate the mechanical effects of sloping the load screw on the axial compression with a dynamic plate. METHODS: Artificial parts simulating shaft fragments were fixated with a 4.5 mm, 7 orifice DCP® plate. A load cell recorded axial compression loads in the space between fragments. Eccentric perforation guides with inclinations to the longitudinal and transversal plan of the plate were made for the experiment. Compression was measured in two different sites of the virtual fracture focus. Eight different groups were formed according to the magnitude of inclination and its direction based on the plate orifice. Mechanical assays recorded maximum load and effective maximum load. RESULTS: Screw inclination contrary to the plate orifice sliding slope was related to decreased mean values of maximum compression load and maximum effective compression load 0º > 10ºi (p < 0,001), 0 > 20ºi (p < 0,001), 0º > 25ºi (p < 0,001). CONCLUSION: In an experimental model, using non pre-stressed DCP® plates, the inclination upon inserting load screws brought about changes in the mean values of axial compression load. There significant differences (p < 0,05) to lower axial compression obtained in the cortical adjacent to the plate when the screws were inserted in inclination with the longitudinal plane in the opposite direction of the sliding slope of the DCP® orifice.
Fracture fixation, internal; Bone plates; Bone screws; Biomechanics
