Study of deformations of bone regenerate under different options of osteosynthesis of lower leg bones in the case of their congenital pseudarthrosis

Abstract

Congenital pseudarthrosis of the leg bones is accompanied by its shortening and deformation. It’s still unclear what is an optimal method of surgical treatment. Objective. Using a mathematical model, to study the relative deformations of the regenerate (RDR) in the zone of pseudarthrosis bones of the lower leg under different options of osteosynthesis. Methods. The zone of nonunion was modeled of the bones of the lower leg third of tibia and 4 variants of osteosynthesis on were analysed: intramedullary rod and needle (1); rod, spoke and bone graft in the form of a block on the tibia (2) or on both (3) bones; rod, spoke and bone with a graft on both bones of the leg with wrapping titanium mesh (4). A rotationally stable and unstable rod was used. Under the influence of the load on compression and torsion determined the values of RDR in the zone of pseudarthrosis. Results. In the case of osteosynthesis of option 1, intramedullary rods of both types (due to axial mobility of their elements) do not provide minimal deformation regenerates of both bones, so there is a possibility of their growth during the growth of the patient. Bone blocks grafts (options 2 and 3) take over part of the compressive load and the level of the RDR of the bones decreases up to 20 times. Rotationally stable rod is better under conditions of torsional loads, since RDR of the tibia is reduced by 20 times. However, bone graft blocks negate this advantage, providing rotational stability of bone fragments lower legs. The use of titanium mesh provides an additional strength of fixation of fragments of both tibia bones and level RDR of bones is reduced by 10 % compared to models of osteosynthesis with a block of grafts for both loading options. Conclusions. The use of only intramedullary rods that «grow» leads to the greatest deformations of regenerates. A rod with rotational stability is better under torsional loading conditions. Blocks from bone grafts reduce the level of RDR of bones tibia to a level of less than 0.1 % for both loading options, and the titanium mesh to an additional 10 %.