The Influence Of The Number Of Screws On Bending Stiffness And DCP Strain In An In Vitro Fracture Model

ObjectiveTo investigate the effect of the number of screws on the bending stiffness and dynamic compression plate (DCP) strain in an in vitro transverse fracture model.MethodsThirty wooden sticks of the chestnut were separated into five groups at random,every group included six specimens.To model a fracture,every stick was cut transversely in the median and a twelve-hole dynamic compression plate was attched by screws.Three rectangular strain gauges were installed on the each plate to evaluate the strains.The axis of each gauge element was mounted longitudinally so as to measure the surface strain of DCP in response to three-point bending.Screw position of the five groups were: A 1-6, B 1-2-6, C 1-2-3-6, D 1-2-3-4-6, E 1-2-3-4-5-6.Thirty plate-screw constructs were test respectively,all strain readings of plate ,including these readings of plate inserted on the compression side and those on the tension side,were compared each other.A probability level of P<0.05 was considered significant.ResultsAmong all groups, this investigation revealed no significant difference about the bending stiffness and median plate strains in three point bending whilst the mean plate strains in A were significantly higher than those in the other groups(P<0.05);The strains in the median region of plate were highest in all the part of adjacent screw hole and decreased longitudinally along the plate.The strains on the tension side were significantly less than those on the compression side(P<0.01).ConclusionsIn a model simulating a transverse fracture,this study showed that the symmetrical omission of screws ,with a given plate length and working length ,did not affect significantly the bending stiffness and median plate strain while the mean plate surface strains might increase;the insertion of plate must complied with the tension band principle.