Cyclic failure analysis of sternal fixation techniques

The aim of this study was to test the hypothesis that sternal fixation failure occurs as a result of the repetitive cyclic loading of low loads as opposed to instantaneous loading of high forces which have been studied elsewhere. To achieve this aim, samples of bisected porcine sternum were reapproximated and fixed using wires or plates and subjected to cyclic application of low magnitude forces to simulate breathing. Cortical and cancellous screw-plate fixation systems were compared, and traditional, simple straight wiring was used as a control. A servohydraulic testing system was used to apply low forces (67N±22N,~ 15 lbs) at low frequency (2 Hz) for a high number of cycles (~50,000) and displacement between the sternal halves was monitored by an extensometer.