ANALYSIS OF THE STRESS-STRAIN STATE OF THE TIBIAL MODEL IN CASE OF ITS FRACTURE IN THE MIDDLE THIRD WITH VARIOUS TYPES OF OSTEOSYNTHESIS UNDER CONDITIONS OF INCREASING BENDING LOAD

Stroev M. Yu., Berezka M. I., Grigoruk V. V., Karpinsky M. Yu., Yaresko A. V., Subbota I. A.

CLINICAL AND EXPERIMENTAL MEDICINE

Scentific article

Introduction. Currently, there is an increase in fractures of the bones of the lower limb (47.3%), among which 45-56% are diaphyseal fractures of the bones of the lower leg. According to the medical and social expert commission of Kharkov, more than 50% of complications were associated with the treatment of fractures of the bones of the lower leg, which caused 27.9% of disability. Target. To conduct a comparative analysis of the stress-strain state of the tibial bone models in case of its fracture with various types of osteosynthesis under the influence of a bending load, depending on the patient’s weight. Materials and methods. The basic model simulated a fracture of the tibia in the middle third and three types of osteosynthesis using an external fixation device (EFD), an external platinum plate, and an intramedullary nail. The models were studied under the influence of a bending load of 700 N and 1200 N. Results. Normally, with a bending load, the maximum stresses of 9.6 MPa are determined in the distal tibia. When using EFD osteosynthesis, the maximum stress level of 5.7 MPa is observed in the distal fragment of the tibia. During osteosynthesis with an extraosseous plate, the zone of maximum stresses shifts to the fracture zone, where the stresses reach a value of 34.6 MPa. Osteosynthesis with an intramedullary nail provides the lowest stress level of 0.2 MPa in the fracture zone, as well as in the proximal fragment of the tibia – 0.8 MPa. An increase in the load value to 1200 N leads to an increase in the stress values in all elements of the model. When using EFD osteosynthesis, an increase in load to 1200 N causes an increase in the maximum stress level to 9.8 MPa in the distal fragment of the tibia. Similar changes occur in the model with bone plate osteosynthesis. The zone of greatest stresses 59.3 MPa remains at the fracture site. During osteosynthesis with an intramedullary rod, the stresses in the distal and proximal bone fragments increase to 22.5 MPa and 1.4 MPa, respectively. Conclusions. The worst indicators of the stress level in the fracture zone (from 34.6 to 59.3 MPa) and the metal structure (from 220.2 to 377.4 MPa) were determined using a bone plate. Early loads, in this case, can cause bending of the plates, and, as a result, incorrect fusion of the tibial fragments. Osteosynthesis using EFD provides a fairly low level of stress (from 0.3 to 0.5 MPa) in the fracture zone, it is worth noting the lowest level of stress on the device itself (from 89.3 to 153.1 MPa). The lowest stress values in the fracture zone (from 0.2 to 0.3 MPa) and in the proximal fragment of the tibia (from 0.8 to 1.4 MPa) are determined when osteosynthesis with an intramedullary nail is used, the disadvantage of this type of osteosynthesis can be considered a rather high stress level on the rod itself (from 181.4 to 310.9 MPa) and on the fixing screws (from 18.2 to 31.2 MPa).

lower leg,fracture,bend,osteosynthesis.

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«Bulletin of problems biology and medicine» Issue 4 (167), 2022 year, 223-236 pages, index UDK 6.718.5/.6-001.5-089.813:613.65]:004.492](045)

10.29254/2077-4214-2022-4-167-223-236