Study of the stress-strain state in models of various options for osteosynthesis of tibial bones with diaphyseal fractures in the middle third in children with osteogenesis imperfecta and incomplete growth Part 1. Compression

Abstract

Background. Osteogenesis imperfecta is accompanied by multiple fractures of skeletal bones, the development of progressive deformations of the long bones of the limbs and, as a result, the inability to stand and walk. At present, the most promising means for stabilizing bone fragments are intramedullary fixators of various designs. Installation of internal fixators without the possibility of their lengthening during the skeletal growth leads to an increase in the frequency of repeated surgical interventions due to the need for their replacement. The purpose was to investigate the stress-strain state of the lower leg models under the influence of compressive load in conditions of fracture of both bones in the middle third and their osteosynthesis using intramedullary rods of various designs in children with osteogenesis imperfecta and incomplete growth. Materials and methods. A mathematical modeling of osteosynthesis of tibial bones with a fracture in the middle third in children with osteogenesis imperfecta was performed in two options: 1 — using a rod without rotational stability; 2 — a rod with rotational stability of the structure. During the research, the stress-strain state of the model was studied under the influence of vertical compressive load. Results. Under compressive loads, the use of a rod with rotational stability does not lead to any significant changes in the stress-strain state of the model compared to tibial osteosynthesis with a rotationally unstable rod. This can be explained by the fact that before resisting the loads acting along the longitudinal axis of the rods, both rods are unstable, so all loads are carried by the bone structures. This is a “fee” for the opportunity to “grow”. The presence of rotational stability of an intramedullary rod does not have a significant effect on the stress distribution in the models under compressive loading. But it should be noted that when using a rotationally stable rod, the stresses in the distal tibia are slightly reduced, and what is especially important, in the fracture zone too. Thus, a growing rod with a locked rotational movement creates more favorable conditions for the fusion of tibial fractures in the middle third, which is of great importance in the treatment of children with osteogenesis imperfecta. Conclusions. Under the influence of compressive loads, the presence of rotational stability of an intramedullary rod does not provide significant advantages from the point of view of stress distribution in the model of a tibial fracture in the middle third. However, due to the presence of a movable support at the distal end of the tibia, even with a vertical compressive load, a small torque can occur between the bone fragments, which should block the rod with a locked rotational movement. This is the cause for a decrease in the stress in the distal fragment of the tibia.