Study of the mechanical characteristics of external fixation pin anchorage: preliminary results

in vitro testing of pins only makes sense if it is carried out on a material that possesses mechanical characteristics coresponding most closely to those of the bone in vivo. Tests have been carried out on different materials, including wood with 3 mm diameter pins, type C38-1 10-20, manufactured by Jaquet Orthopedic SA.The first step in our investigation was to check the thickness of the material samples tested. The values of the tapping, screwing and shearing torques were measured. For each material, we have calculated the value of the specific screwing torque and the specific shearing torque. There is no significant difference between the values calculated for the tightening and shear specific torques for all the fresh bone samples. For the different types of wood examined, we found an important deviation of torque values, which are much lower than those observed with fresh bone. There exists, therefore, a correlation between the screwing and shearing torques observed and the thickness of the sample. The results obtained certainly allow new types of pins to be developed.