[Influence of an interlocking condition on the fracture healing process]

In order to clarify the influence of interlocking condition on the fracture healing process, the following three studies were carried out. First, an axial loading test was done in which an interlocking nail was inserted into a osteotomised human femoral bone. As a callus substitute, several kinds of resin were packed into the osteotomy gap. Load-formation curves were detected with strain gauges. These experiments suggest that the strain of the fractured end and its substitutes increase as the stiffness of the substitutes increases. Next, three weeks after the fixation with an interlocking nail of the osteotomized rabbit femur, the half of the femora were dynamized. The other half were not. Four to 56 weeks after osteotomy, the femora were harvested for radiographical and histological examination. No significant differences were detected between the two groups. In the last study, static and dynamic condition models similar to the second experiment were made. At 12 weeks, femora were harvested and measured for maximum bending strength. There were no statistically significant differences. These studies suggest that a so-called static condition has no unfavorable effects on fracture healing.