Study of relative deformations of interfragmentary regenerate in models of different osteosynthesis options of tibia bones with fractures in the middle third in children with osteogenesis imperfecta and incomplete growth

Abstract

Introduction. Osteogenesis imperfecta is a genetic pathology that leads to a violation of the processes of formation of collagen fibers, formation of bone matrix and its mineralization and, as a result, to the formation of bone tissue with low strength properties. The most promising means of stabilizing bone fragments under this condition are intramedullary fixators of various designs. Aim. To investigate the relative deformations of the interfragmentary regenerate under the influence of various types of loads in models of the tibia with fractures 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. Mathematical modeling of options for osteosynthesis of tibia bones with a fracture in the middle third in children with osteogenesis imperfecta was performed. Two variants for tibial osteosynthesis were modelled: a rod without rotational stability; rod with rotational stability. Osteosynthesis of the fibula was not modelled in all variants. The stress-strain state of the model under the influence of vertical compressive, bending and torsional loads, as well as the magnitude of the relative deformations of the interstitial regenerate, were studied. The results. A “growing” intramedullary shear with rotational stability provides essential advantages in the case of torsional loads. The presence of rotational stability makes it possible to ensure two times lower values of relative deformations of interfragmentary regenerates compared to osteosynthesis with a rotationally unstable rod. Under compressive and bending loads, both rods showed almost identical results of relative deformations of bone regenerates. High rates of deformation of interfragmentary tibial regenerates are due to the lack of longitudinal axial stability of both rods, which is the basis for the possibility of increasing their length during the growth of the patient. Conclusions. The use of osteosynthesis with intramedullary rods, which increase during the treatment of tibial fractures in patients with osteogenesis imperfecta, does not ensure a sufficient level of stability for the fixation of bone fragments under compression and bending loads, which leads to the greatest deformations of bone regenerates. A rod with rotational stability provides advantages in resistance to torsional loads, which is determined by twice lower relative deformations of interfragmentary regenerates. No conflict of interests was declared by the authors.