Biomechanical analysis of bar placement level during surgical correction of pectus excavatum, Біомеханічне обґрунтування місця проведення пластини при хірургічній корекції лійкоподібної деформації грудної клітки

<jats:p>Background. Minimally invasive thoracoplasty using the D. Nuss technique remains the standard treatment for pectus excavatum. However, interaction between the implant and the thoracic framework is frequently associated with complications, including bar displacement and chronic pain syndrome. Most contemporary studies investigating the stress-strain state focus primarily on the “sternum-ribs” complex without considering the spinal column and the mobility of the costovertebral joints. Objective: to perform a comparative analysis of stress-strain distribution patterns in the biomechanical “sternum-ribs-spine” system during surgical correction of pectus excavatum depending on the anatomical level of bar placement. Materials and methods. A finite element mathematical model of the chest wall was developed, incorporating the spinal column and physiological mobility of the costovertebral articulations. Two thoracoplasty techniques were compared: conventional placement of a short bar through the IV–V intercostal spaces and placement of a custom-designed bar through the VI–VII intercostal spaces. Modeling was performed ­using SolidWorks and ANSYS software. Stress distribution was evaluated according to the von Mises equivalent stress criterion. Results. With conventional bar placement through the IV–V intercostal spaces, maximum stresses in the supporting ribs reached 22.4 MPa, while stresses in the spinal structures reached 9.9 MPa. In contrast, placement of the custom-designed bar at the VI–VII intercostal level reduced maximum stresses to 14.0 MPa in the ribs and 2.4 MPa in the vertebrae. A more uniform load distribution within the “sternum-ribs-spine” system and reduced overload of the costovertebral joints were observed. Moderate stress elevation in the “bar-sternum” contact zone did not produce a critical effect on osseous structures. Conclusions. Placement of the corrective bar through the VI–VII intercostal spaces provides more favorable biomechanical characteristics compared with the conventional technique. The use of a custom-designed bar reduces stress levels in the ribs and spinal structures, improves load distribution, and may potentially decrease the risk of postoperative complications following surgical correction of pectus excavatum.</jats:p>