The Effects Of The Number Of The Screw In The Plates On The Bending Stiffness Of Plate And Screw Structure

Objective: To investigate the effects of the number of the screw in the dynamic compression plates on the bending stiffness of plate and screw structure in vitro. Methods: Thirty wooden sticks of the chestnut were divided into five groups randomly. Every stick was cut transversely in the median and a twelve-hole dynamic compression plate was attached by screws. Three sensor gauges were installed on each plate to evaluate strain. Screw number 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. Each group was tested by three point bending.Results: In three point bending, the strain in the fracture model was highest in group A (895.67 ± 36.06 μ ε ) and lowest in group E (817.50 ± 26.83 μ ε ) . There is significant difference (p<0.05 ) in the strain between group A and C (832.17 ± 25.39 μ ε), D( 830.00±30.04 μ ε),E. There is also significant difference (p<0.05) in the strain between group B(874.83 ± 35.28 μ ε )and D, E.There is no significant difference(p>0.05)in the strain between A and B, B and C, C and D,C and E, D and E.Conclusions: The screw number has effect on the stiffness of the plate and screw structure as the same plate length in three point bending. In the definite condition of the screw number achieved, increasing the screw number does not increasing the structure stiffness.