Stress-strain state of fibrin-blood clot and periosteum in the area of diaphyseal fracture under different conditions of fracture fragments fixation and its impact on the structural organization of regenerate

Abstract

The goal: using mathematical finite-element modeling to calculate the stress-strain state (SSS) of fibrin-blood clot and periosteum around the fracture zone in the conditions of fixation of femur fragments with on-bone plate, intramedullary locking nail and ExFix. The methods: the model represents two fragments of femur with transverse fracture plane joined with spindly fibrin-blood clot enclosed in periosteum and devices mentioned above. The existing data on the Young's modulus and Poisson's ratio of all components of the model were used. The calculations of SSS of clot and periosteum were performed under axial load of 800 N on femur and transverse load of 200 N on the distal femur. The control points on the horizontal section of clot and periosteum were selected for a quantitative comparison of the voltage in various conditions of fragments fixation. Moreover, the area covered by the maximum stress level was compared. The results: The following patterns were revealed. At the same axial load of model the lowest level of stress in periosteal-fibrin spindle was observed when fragments were fixed with intra­medullary locking nail, a little more — with plate, and the biggest one — with ExFix. The ratio of the stress values was 1: 2: 3–4.At the same transverse load of model the lowest level of stress in periosteal-fibrin spindle was observed when fragments were fixed with plate, a little more – with intramedullary locking nail, and the biggest one — with ExFix. The ratio of the stress values was 1: 6: 10–12.The greatest difference in stress levels was noticed in the conditions of transverse load on the segment. Conclusion: The presented data on SSS in tissues around the fracture zone explain the origin of sizes, shapes and structures of periosteal bone regenerate in the treatment of diaphyseal fractures with devices with different modes of mobility of bone fragments.