Influence of sternal size and inadvertent paramedian sternotomy on stability of the closure site: a clinical and mechanical study

BACKGROUND: The influence of sternal size and of inadvertent paramedian sternotomy on stability of the closure site is not well defined. METHODS: Data on 171 consecutive patients undergoing cardiac surgery through a midline sternotomy were prospectively collected. Intraoperative measurements of sternal dimension included thickness and width at the manubrium, the third and fifth intercostal spaces; paramedian sternotomy was defined as width of one side of the sternum equaling 75% or more of the entire width, at any of the three levels. The chest was closed with simple peristernal steel wires and inspected to detect deep wound infection and/or instability for 3 postoperative months. The sternal factors and several patient/surgery-related factors were included in a multivariate analysis model to identify factors affecting stability. An electromechanical traction test was conducted on 6 rewired sternal models after midline or paramedian sternotomy and separation data were analyzed. RESULTS: Chest instability was detected in 12 (7%) patients and wound infection in 2 (1.2%). Patient weight (P = .03), depressed left ventricular function (P = .04), sternum thickness (indexed to body weight, P = .03), and paramedian sternotomy (P = .0001) were risk factors of postoperative instability; paramedian sternotomy was the only independent predictor (P = .001). The electromechanical test showed more lateral displacement of the two rewired sternal halves after paramedian than midline sternotomy (P = .002); accordingly, load at fracture point was lower after paramedian sternotomy (220 +/- 20 N vs 545 +/- 25 N, P = 0.001). CONCLUSIONS: Inadvertent paramedian sternomoty strongly affects postoperative chest wound stability independently from sternal size, requiring prompt reinforcement of chest closur