https://www.annalsthoracicsurgery.org/article/S0003-4975(08)02019-5/pdf

Prevention of Sternal Dehiscence and Infection in High-Risk Patients: A Prospective Randomized Multicenter Trial

The paper gives a bibliographical review of the finite element modeling and simulations in orthopedics from the theoretical as well as practical points of view. The bibliography lists references to papers, conference proceedings and theses/dissertations that were published between 1998 and 2005. At the end of this paper 1264 references are given dealing with subjects as: bones and their parts, special tissues; spine mechanics; movable joints and computational modeling.

Finite element modeling and simulations in orthopedics: a bibliography 1998–2005

OBJECTIVES: Biomechanical modelling of the forces acting on a median sternotomy can explain the mechanism of sternotomy dehiscence, leading to improved closure techniques. METHODS: Chest wall forces on 40 kPa coughing were measured using a novel finite element analysis (FEA) ellipsoid chest model, based on average measurements of eight adult male thoracic computerized tomography (CT) scans, with Pearson’s correlation coefficient used to assess the anatomical accuracy. Another FEA model was constructed representing the barrel chest of chronic obstructive pulmonary disease (COPD) patients. Six, seven and eight trans-sternal and figure-of-eight closures were tested against both FEA models. RESULTS: Comparison between chest wall measurements from CT data and the normal ellipsoid FEA model showed an accurate fit (P< 0.001, correlation coefficients: coronal r = 0.998, sagittal r= 0.991). Coughing caused rotational moments of 92 Nm, pivoting at the suprasternal notch for the normal FEA model, rising to 118 Nm in the COPD model (t-test, P< 0.001). The threshold for dehiscence was 84 Nm with a six-sternal-wire closure, 107 Nm with seven wires, 127 Nm with eight wires and 71 Nm for three figure-of-eights. CONCLUSIONS: The normal rib cage closely fits the ellipsoid FEA model. Lateral chest wall forces were significantly higher in the barrelshaped chest. Rotational moments generated by forces acting on a six-sternal-wire closure at the suprasternal notch were sufficient to cause lateral distraction pivoting at the top of the manubrium. The six-sternal-wire closure may be successfully enhanced by the addition of one or two extra wires at the lower end of the sternotomy, depending on chest wall shape.

/pdf/mechanism-of-sternotomy-dehiscence-1euxguaml1.pdf

Mechanism of sternotomy dehiscence

Failure of a sternotomy closure because of closure system fatigue is a complication that may result in dehiscence and put the individual at risk for serious complications. The purpose of this study was to assess the fatigue performance of three peristernal median sternotomy closure techniques (figure-of-eight stainless-steel wires, figure-of-eight stainless-steel cables, or Pectofix Dynamic Sternal Fixation [DSF] stainless-steel plates) in order to quantify the potential risk of fatigue failure of these devices when subject to cyclic loads in physiologically relevant loading directions. All tests were conducted on polyurethane foam sternal models. A cardiothoracic surgeon divided each sternal model longitudinally and repaired it with a closure device. Tests were performed using a materials testing system that applied cyclic loading in a uniaxial direction until the test model catastrophically broke or data run-out occurred. For each loading direction (lateral distraction and longitudinal shear), five trials of each closure technique were tested. Life data and location of device failure (if present) were evaluated. Statistical analysis was performed using regression with life data allowed for correlation between life data and the various closure techniques to develop risk assessment curves for each device. The data show that the figure-of-eight stainless-steel cable and the DSF plate systems are considerably less likely to fail under both lateral distraction and longitudinal shear cyclic loading conditions as compared to the figure-of-eight stainless-steel wire system. Moreover, the figure-of-eight stainless-steel cable system is the most resistant to failure, particularly for high cycle counts. This study in addition to Cohen and Griffin's earlier published biomechanical comparison of the ultimate strength of these same three closure techniques provide extensive experimental evidence regarding the mechanical differences among these three peristernal median sternotomy closure techniques. All data support the hypothesis that both the DSF plate system and the stainless-steel cable system offer important advantages over figure-of-eight wire closure techniques; although twisted wires are the weak-link in the systems we tested.

/pdf/fatigue-testing-of-three-peristernal-median-sternotomy-42nuuixdfc.pdf

Fatigue testing of three peristernal median sternotomy closure techniques

SUMMARY

In this paper, the application of new visualization technologies in correction of funnel chest is presented. Often, such defects cause problems with breathing, and therefore, to improve the cardiorespiratory efficiency, a correction is required. The virtual model of chest was formulated to determine the strains and stresses after correction of deformation with using the stabilizing plate. From biomechanical point of view, the knowledge of the load-affecting stabilizer is necessary to select optimal parameters of the plate. The force-affecting plate that was used in the correction of chest deformation by Nuss method was determined on the basis of finite element model of funnel chest. The main aim of this work was to select the optimal thickness of plate. Calculations were conducted for three alternative constraints. Copyright © 2013 John Wiley & Sons, Ltd.

Dagmar Hintze

Papers

Numerical simulation techniques to study the structural response of the human chest following median sternotomy.