Influence of Oscillation Drilling on Screw Purchase: A Biomechanical Pilot Study

Oscillation drilling (OD) commonly is used in orthopaedic surgery to minimize soft tissue damage and control drill advancement, thereby reducing the risk of "plunging" through cortical bone. However, its effect on screw purchase compared to forward drilling (FD) remains unstudied. The purpose of this study was to compare maximal insertional torque (MIT), a proxy for screw purchase, following OD and FD in a synthetic bone model.

Pilot holes were drilled into synthetic femoral shaft models using OD and FD with three drill bit sizes (2.0 mm, 2.6 mm, and 3.2 mm). Corresponding self-tapping stainless-steel screws (2.7 mm, 3.5 mm, and 4.5 mm) were inserted into the pilot holes. MIT was measured during screw insertion using an axial torsion testing device, with five trials per condition.

For 2.7 mm screws, mean MIT was 195.8 ± 47.0 N·cm (FD) versus 232.8 ± 11.8 N·cm (OD); for 3.5 mm screws, 336.8 ± 100.6 N·cm (FD) versus 357.4 ± 150.7 N·cm (OD); and for 4.5 mm screws, 943.5 ± 551.8 N·cm (FD) versus 1089.2 ± 232.2 N·cm (OD). No statistically significant differences in MIT were found between FD and OD across screw sizes (p = 0.85), although MIT increased significantly with the 4.5 mm screws (p <0.001).

OD and FD produced comparable screw purchase across screw sizes, suggesting that either technique may be used without compromising fixation strength in orthopaedic applications.