Mathematical Modeling of the “Bone-Fixator” System during the Treatment of Intertrochanteric Fractures

Abstract

Relevance — the need for an objective justification in choosing the type of fixation in the treatment patients with pertrochanteric hip fractures.Objective — to study the changes in the properties of a consolidating trochanteric fracture fixed by a dynamic cephalomedullary nail when subjected to cyclic dynamic loads.Materials and methods. A mathematical model was developed for trochanteric fracture of the femur (A1 according to AO classification) when fixed with a dynamic cephalomedullary nail. Then, the properties of the system were studied (pressure between fragments, mechanical stress in the bone and fixation device, displacement amplitude, neck-diaphysis angle) under a virtual load of a 80 kg body at various amount of insertion of the dynamic screw (from 10 mm to 0 mm).Results. In the process of shortening the femoral neck axis by 1 cm, the stability of the ‘bone-metal fixation device’ system increases, as indicated by a decrease in the maximum amplitude of displacements in the system under load by 16.8%, a decrease in the maximum stress in the fixation elements by 20.2%, a decrease in pressure at the site of contact of fragments by 19.8%. In addition, there was a decrease in the neck-diaphysis angle by 2.8%.Conclusion. The mathematical modeling of the ‘bone-metal fixation device’ system simulating conditions of dynamic osteosynthesis showed that there is a potential increase in the stability of the cephalomedullary system and that favorable conditions are created for the consolidation of the fracture when subjected to cyclic load of body mass.

Keywords

• dynamic cephalomedullary osteosynthesis
• finite element analysis
• trochanteric fractures