Biomechanical analysis of prophylactic fixation for middle third humeral impending pathologic fractures

For determination of the most biomechanically desirable construction for pr ophylactic fixation of impending central 1/3 humeral fractures, 24 matched pairs of fresh frozen skeletonized human cadaveric humeri were divided rand omly into four groups. Group 1 compared intact humeri with matched humeri t hat had a 50% hemicylindrical cortical central 1/3 defect to show reproduci ble failure at the defect with significant reduction in strength. Groups 2 through 4 compared prophylactic fixation of the defect combined with cement ation and dynamic compression plating, Rush redding, or locked intramedulla ry nailing. Each specimen was tested in external rotation torsion to failur e by fracture. In Group 1, test specimens with defects failed with signific antly lower rotation to failure, peak torque, stiffness, and total energy a bsorbed to failure. In Groups 2 through 4, intramedullary nailing provided statistically significantly better total energy absorbed to failure and sti ffness than did dynamic compression plating. The proximally and distally lo cked intramedullary nail seems to have biomechanical advantages in the prop hylactic stabilization of an impending pathologic fracture of the central 1 /3 Of the humerus, These biomechanical findings must be considered in light of the clinical context when a means of fixation is selected.