Effectiveness of resisting torsional loads of various options for osteosynthesis of tibial fragments (according to the results of mathematical modeling)

Abstract

Recently, there has been a trend towards high statistical indicators of the number of bone fractures of the lower limbs(47.3%), of which diaphyseal fractures of the lower leg bones make up 45‒56 %. Objective. Conduct a comparative analysisof the stress-strain state of leg models with a fracture of the tibia under the torsional loading combined with various optionsof osteosynthesis and depending on the patient's weight. Methods. A fracture was modeled in the middle third of the diaphysisof the tibia and three types of osteosynthesis — with the help of an external apparatus fixation (EAF), periosteal plate andintramedullary rod Bones were attached to the tibial plateau torque of 7 Nm and 12 Nm. Results. It was determined thatthe changes in stress levels in bone tissue depend linearly on the patient's weight. Under simulation conditions stabilizationof the fracture with the help of EAF and intramedullary stress rod in the fracture area were found significantly lowerthan the level of indicators of intact bone. In this same zone in the model with a bony plate, the value stress levels were lowerthan the intact model bone, but with an increase in the patient's weight to 120 kg, these indicators almost leveled off. The highest stress level was recorded in the distal part of the tibia in the model with intramedullary rod osteosynthesis, and inthe proximal one, the stresses that exceeded the parameters of the model with intact bone were determined under the conditions use of EAF. The largest in metal structures stress is detected in the periosteal plate. Conclusions. The highest stresses in the fracture zone (5.8‒9.9 MPa) and on the metal structure (360.0‒617.0 MPa) was recorded in a model with a bone plate. In the model with EAF in the zone of the fracture, the stresses were at the level of 0.1‒0.2 MPa, in the proximal part of the tibia — 6.3‒10.8 MPa, in the model with an intramedullary rod — 0.1‒0.2 MPa and 0.5‒0.9 MPa, respectively. In the distal partof the stress in the last model remained high — 11.7‒20.1 MPa.