An experimental study on the effects of the plating method for bone fractures--with reference to bone union and bone strength (author's transl)

The plating method for bone fractures is in wide use. The author studied both new bone formation and bone atrophy of the cortex of fracture site after long periods of plating. This study is concerned with the bone strength of the fracture site as influenced by rigid plate fixation, and also with bone union after the removal of the plate. The experimental results, using mature rabbits as subjects, showed the following: X-rays of the bone union at the fracture site treated by the plating method confirmed evident union at 8 weeks after surgery. The bone strength at the region of this union, as tested by the bending method (an Instron Type Testing Machine was used), showed its highest values at 28 weeks after surgery. Yet, this was only 60% of the bone strength as measured at a non-fracture site; it then gradually declined in strength. On the other hand, in the case where the plate had been removed 8 weeks after surgery, bone strength was recovered to the same level as that of non-fracture sites 16 weeks after surgery. In conclusion, rigid plate fixation for a long period may result not only in progressive bone atrophy of the cortex but also in a delayed remodeling of the bone at the region of the bone union. It is, therefore, very important to remove the plate as early as possible once union has been achieved. Careful observation, however, is necessary during the short time between plate removal and the period when bone strength becomes again normal.