Determination of Stresses in the Apparatus of External Fixation of the Human Spine
This present work aims to increase the effectiveness of the spine external fixation device by optimizing its stress-strain state. Insufficient studies of the problems of the stress-strain state of the pedicle screw closure vertebra column, as well as the occurrence of dangerous stresses in the pedicle screw with various combinations of control efforts, are made to correct spinal deformity with a large factor of safety. In many cases, it is not possible to create the required correction action on the spine. A high degree of statistical determination of the structure, the ambiguity of the impact of the device on the vertebrae, and the change in the internal control efforts in adjusting the distraction rods limit the use of external fixation for complex spine deformities. Determination of stresses in dangerous sections of rods-screws depending on the control actions is the basis for mathematical modeling of the process of correction. An algorithm for mathematical modeling of the stress-strain state of the external fixation apparatus of the spine is proposed. By calculationand experimentation, we were able to determine the mechanical stresses in the dangerous section of the structural elements of the device. To prevent dangerous stresses when turning the vertebrae, it is necessary to apply asymmetrical multidirectional load. With complex deformities of the spine, an additional impact of a couple of forces is necessary to turn the vertebrae.