[Stimulation of collagen synthesis in rabbit tendons by continuous extension stress]

In a series of three experiments we tried to find out early changes of mechanical properties and of collagen synthesis induced by continuous loading in rabbit tendons. Unphysiological elongation of the calcaneus tendon was performed by distraction of the osteotomized lower leg with the aid of an external minifixator. In the first experiment, the stretched tendons and the unstretched tendons of the contralateral legs were excised 24 hours postoperatively and compared. Collagen-synthesis was measured using 3H-Proline. After 24 hours' stretching a clear increase of 3H-Proline as a sign of collagen new-formation was found in only three out of five animals. In the second experiment, stress-strain measurements were performed after 24 hours of loading. In paired tests a clear difference was not found. Therefore, loading was extended to 48 hours in the third experiment. 3H-Proline was measured as well as the mechanical properties in paired tests. The median increase of the 3H-Proline level was significant: 44%. Stress-strain behaviour was investigated using a special testing equipment. This enables us to perform strain controlled tests in order to find out the mechanical properties of the different specimen.