16.0: Thursday, March 17, 2005

Biomechanics of the Sternum and Correction of Sternal Deformities

Roger S. Collins, MS, MD

Recently, abundant attention has been given to rigid sternal fixation after median sternotomy and for sternal reconstruction using screw and plate techniques. Several studies have characterized sternal physiology and more are in process. No recent studies have looked at sternal physiology with the goal of correction of congenital sternal deformities. This study looks at the pull out strength of sternal fixation screws and plates in a cadaveric porcine model. Single screw and multiple screw/plate combinations were studied. Single screw pull out strength was found to be highly variable in this model. Nonetheless, the average single screw pull out strength of 2 and 2.7 mm bicortical locking screws was studied. As expected, screw pull out strength increased with larger diameter screws and thicker bone media. In multiple screw models, pull out strengths were at least additive. In addition, placing screws at moderate opposing angles increased device pull out strength as expected. Based on these findings, there may be a role for sternal fixation devices or variations of these devices in the active manipulation of congenital sternal deformities.