[Dynamic study of miniplates by finite element method].

Three-dimensional analysis by means of the finite element method was made of displacement and principal stress at various parts of plates and bone fragments. The plates were 4 Champy, AO, Luhr, Steinhäuser 4-hole, short miniplates (Plates 1,2,3, and 4) and Plate 5, which was the same as the others except that it was made of titanium. To all of these plates loads were applied in the directions of the Y and Z axes on the free(right)ends. The plates were fixed in place by means of screw holes 1 and 2 in the left ends. In addition, various kind of osteosynthesis were performed on 2 bone fragments with Plate 1. The left ends of these fragments were fixed in place, and loads were applied to the free(right)ends in the Y and Z axes. 1) When load was applied in the direction of the Y axis, displacements along the Y and X axes were greatest in the case of Plate 5 and next greatest in Plate 1. Displacement along the Z axis was greatest in Plate 3 and next greatest in Plate 5. Displacement along the X axis was least in Plate 3 and displacement along Y and Z axes were least in Plate 4. 2) When load was applied in the direction of the Z axis, displacements along the all axes were greatest in Plate 5, next greatest in Plate 1, and least in Plate 4. 3) In all plates, when load was applied in the direction of the Y axis, maximum principal stresses occured above the region between screw holes 2 and 3. Minimum principal stress, however, concentrated below the area between screw holes 2 and 3 in all models. 4) In all plate models, when loads was applied in the direction of the Z axis, maximum principal stresses concentrated in the outer central part of each plate in the region between the vicinity of the right edge of screw hole 2 and the vicinity of the left edge of screw hole 3. Minimum principal stress, on the outer hand, concentrated in the inner middle region of the plate in a zone corresponding to that in which maximum principal stress concentrated.(ABSTRACT TRUNCATED AT 400 WORDS)