A mathematical analysis of alternative sternal wound closures--an aid to reducing cardiac surgical mortality.

Sternal dehiscence is an important complication of cardiac surgery. A simple mathematical analysis is described for determining the relative strength (S) of different types of sternal closure. This is based upon resolving the tensions within the segments of a sternal wire to derive a dehiscence force. The strength of the closure (S) is the ratio of the volume of sternum which the dehiscence force acts upon to the dehiscence force itself. The derived S values varied from 4.3 for a closure using 6 transverse wires to 11.4 for a closure using the Modified Technique. The analysis suggested that closures which redistribute the transverse force to act obliquely upon a greater volume of sternum, such as the Modified Technique, are less likely to fail.