The Effects Of The Position Of The Screw In The Dynamic Compression Plates On The Stability Of Plate And Screw Structure

Objective: To investigate the effects of the position of the screw in the dynamic compression plates on the stability of plate and screw structure in vitro. Methods: Twenty-four wooden sticks of the chestnut were divided into four 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 position of the four groups were: A:1-2-6; B:1-3-6; C:1-4-6; D:1-5-6. Each group was tested by three point bending and torsion. Results: In three point bending, maximal plate strain in the fracture model was lowest in group A(774.50±18.00με) and highest in group D(849.67±44.03με) . There are significant differences(p<0.05) for each variable in group A, B(816.33±25.43με), C (838.83±31.80με) and D except between B and C(p>0.05). In torsion, there are no significant differences(p>0.05)among variable groups; A(236.83±72.11με),B(210.00±118.17με),C(242.83±129.60με),D(249.33±47.10με). Maximal plate strain was in the fracture site and minimal plate strain in the end of the plate on each sample. Conclusion: As the same plate length and screw numbers, screw position affects the stability of dynamic compression plate structure in three point bending and does not affect the stability of dynamic compression plate in torsion.