Comparison of thorax support systems after median sternotomy: Evaluation of force distributions in a biomechanical analysis

Aims: The incidence of severe sternal wound complications cardiac patients presents a significant need for more sternal stabilization after median sternotomy procedures. Prospective randomized studies showed a significant benefit using the Posthorax sternum support vest. This current study provides a biomechanical analysis of the distribution of force after median sternotomy evaluating the efficacy of different thorax support systems. Material and methods: A thorax model with artificial respiration was built to perform repeatable measurements to proof the forces after median sternotomy. Two thorax support systems were compared: a usually used elastic bandage and the Posthorax® sternum vest. Two strain gages and a potentiometer were used to prove distributions between the sternum halves. The value of the pressure measurements were calculated computer assisted with the FEM software to analyze stress and deformation. Results: Tractive forces of the sternum halves after median sternotomy were 30.8±4.4 N without any kind of external support. These forces could be reduced to 20.5±7.1 N with the elastic bandage and to 7.4±2.9 N with the Posthorax support vest (p<0.05). Values are evaluated if the support vest is not properly fitting up to 16±8.4 N. Conclusion: In this biomechanical model the effectiveness of the Posthorax support vest after median sternotomy could be demonstrated by reduction of force distributions of the sternum halves. These findings explain the reduced movement of the sternum and increasing stability using a proper thorax support system.