STUDY OF THE DISTRIBUTION OF STRESSES IN THE ELEMENTS OF THE STERNO-COSTAL COMPLEX AND METAL PLATES IN THE CASE OF MINIMALLY INVASIVE CORRECTION OF THE FUNNEL-SHAPED DEFORMATION OF THE CHEST ACCORDING TO NUSS

Abstract

In severe forms, funnel-shaped chest deformity (FSCD) requires surgical correction. The method of choice is the Nuss operation and its modifications. Objective. To study the changes that occur in the stressed-deformed state of the chest model and the fixator under different methods of its implementation during the minimally invasive correction of FSCD according to Nuss. Material and methods. 4 schemes of FSCD correction were modeled: 1 — alignment with one retrosternal plate with transverse stabilizers, the point of entry and exit of the fixator is located parasternal at the level of the bone-cartilage transition, the fixator on the sides of the chest ends at the level of the front axillary line; 2 — sternal plate with transverse stabilizers, the point of entry and exit is located at the level of the front armpit line, the fixator ends at the level of the middle armpit line; 3 — the use of a double plate with transverse bars that connect the plates with the help of screws with medial conduction; 4 — a double plate with transverse slats, which connect the plates with the help of screws with lateral guidance. The models were loaded with a distributed force of 100 N applied to the sternum. The results. When using FSCD correction schemes, the maximum level of stress occurs in the metal plates, because they bear the main loads from the sternum, which tries to return to its original position after correction. The same reason causes the highest level of stress among the elements of the skeleton in the sternum. Conclusions. Under the conditions of using any FSCD correction scheme, the maximum stress level occurs in the metal plates, sternum, fifth and sixth ribs, which are in direct contact with the plates. The use of long plates with lateral points leads to a slight decrease in stress values in all elements of the model. The «Bridge» fastener allows you to significantly reduce the level of stress, both in the plates themselves and in the elements of the skeleton due to an increase in their contact area.