Method of fixing titanium pectus bar in surgical correction of funnel chest and its mathematical modeling
Authors:   Municipal non-profit institution «Zhytomyr Regional Pediatric Clinical Hospital» Zhytomyr Regional Council», Ukraine, Zaremba V.R. , Kyrychenko V.A. ,   National University «Yuri Kondratyuk Poltava Polytechnic», Ukraine
Published: September 2021

The most common surgery for the correction of congenital funnel chest in the 21st century is the Nuss procedure. This intervention is accompanied by complications related to the actual fixing bar and its size and placement and methods of fixing. The most common of these are bar displacement and chronic postoperative pain. Only one size of corrective bar (thickness, width) is used for this type of operation in all age groups. Purpose – to develop and implement the original modification of the Nuss procedure with individual calculation of the minimum dimensions of the corrective bar; to eliminate the probability of bar displacement; reduce the duration and intensity of postoperative pain. Materials and methods. The original method of the correcting titanium bar fixing as a monolithic metal arched structure with rigidly fixed ends was used in the study, the subperiostal fastening of the bar stabilizers to two ribs on each side was used. This method was used to operate on 34 patients with funnel chest aged from 6 to 17 years. Results. Mathematical modeling of the functioning of the correcting bar as a monolithic metal arched structure with rigidly fixed ends and determination of its strength and rigidity were performed. As an example, when calculating the stiffness of a plate with a width of 12 mm and a thickness of 2.2 mm under the use of a load of 25 kg (250 N) and an arch width of 20 cm, we determine the deflection of the bar 3.57 mm, strength factor 1.8. The loads of 250 N are much higher than those that actually exist. The cases of depression of the thorax (deflection of the bar) and cases of eruption of the bar were non indicated. The analyzis the level of postoperative pain syndrome on the NRSP scale for 4–5 days after surgery in patients with II degree of funnel chest determined an average score of 3.74; with III degree – 4.18; after one month of the operation – 1.0 and 1.63, respectively. Chronic postoperative pain was not noted. Conclusions. Rigid subptriostal fixation of the bat stabilizers to two ribs on each side prevents the plate from shifting. The proposed method of mathematical modeling of plate dimensions allows to individually calculate the dimensions of the correcting bar, providing in the vast majority of cases the correction of deformation bars 10, 11, 12 mm. The intensity and duration of the pain syndrome is much less than in standard technique due to the redistribution of pressure on the fulcrums of the bar and the absence of injury to the intercostal nerves, reducing the size of the plate. The research was carried out in accordance with the principles of the Helsinki declaration. The study protocol was approved by the Zhytomyr Regional Pediatric Clinical Hospital of the Zhytomyr Regional Council, Ukraine. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: Nuss procedure, funnel chest, fixing bardimensions, method of fixation.