Kirschner wire prepared pilot holes improve screw pullout strength in synthetic osteoporotic-type bone

Objectives: To compare the pullout strength and maximal insertional torque of pilot holes prepared with the traditional twist drill bit versus a smooth Kirschner wire. Methods: Pilot holes were prepared using a drill press with either a 2.5 mm twist drill bit or a 2.5 mm smooth Kirschner wire into 2 distinct polyurethane foam densities representing severe and mild osteoporotic bone. 3.5 mm cortical and 4.0 mm cancellous screws were then inserted freehand into the prepared holes. All permutations of pilot hole type, screw size and foam density were tested for maximum pullout strength and maximum insertional torque. Results: Kirschner wire prepared pilot holes resulted in significantly higher pullout load than drill bit holes in low density blocks (P < 0.001), but not in high density blocks (P = 0.232). There was no statistical difference (P > 0.05) for maximum insertional torque in the pilot hole preparation type. Conclusion: In severely osteoporotic bone, Kirschner wire pilot hole preparation may improve screw pullout strength.