Аналіз математичного моделювання біомеханічної моделі гало-гравітаційної тракції при деформаціях хребта в дітей

Abstract

Halo-gravity traction (HGT) systems are widely used in leading clinics around the world as a staged method for correcting complex (>100°) scoliotic deformities of the spine in children. Today there is no single approach to the use of this technique, and each doctor makes a decision regarding the treatment regimen empirically, based on his clinical experience. Purpose – to investigate with the help of finite element method the stress-strain state of the spine of various degrees of deformation using HGT. Materials and methods. When constructing the computational model, geometric models of various parts of the spine, developed in the laboratory of biomechanics of the State Institution «IPPS named after I.P. Sitenko of the National Academy of Medical Sciences of Ukraine». The following changes were made to the model, in accordance with the purpose of the study: spinal deformity 70° and 100°; added skull model; added model of HGT and its fixation to the skull. Results. When using the HGT system with fixation, the most loaded part of the spine is the T2-T5 vertebrae. It should be noted that with an increase in the degree of deformity, the T4 and T5 vertebrae become loaded. The HGT system with fixation and load equal to half the body weight does not lead to critical values of bone tissue stress in terms of strength. Results. In the treatment of rigid spinal deformities in children with a deformity angle (>100°) using a HGT system, the first stage mathematically proved the effectiveness of this technique, but the maximum recommended load should not exceed 50% of the patient’s body weight. Modeling the correction of spinal deformities using mathematical models makes it possible to analyze the effect of various treatment methods in several versions without surgery. The maximum von Mises stress value of 40.1 MPa is not critical for bone tissue in terms of strength (ultimate strength for cortical bone is 70 MPa). However, when the load is doubled, i.e. with HGT to a load equal to the body weight, the level of stress will also double and exceed the ultimate strength of the bone tissue. The research was carried out in accordance with the principles of the Helsinki declaration. The study protocol was approved by the Local ethics committee of all participating institutions. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: final element method, spinal deformity, halo-gravity traction.