Biomechanical Evaluation of Mini-Fragment Hardware for Supination External Rotation Fractures of the Distal Fibula

Abstract

Background. Supination external rotation distal fibula fractures are common, requiring fixation when associated with talar displacement. Subcutaneous distal fibula hardware may become painful, necessitating operative removal. We hypothesize that mini-fragment and small-fragment constructs will demonstrate similar biomechanical stability. Methods. A biomechanical comparison was performed in synthetic osteoporotic sawbones. The first arm compared two 2.4-mm lag screws with one 3.5-mm lag screw for fixation of a simulated supination external rotation distal fibula fracture. The second arm compared a 2.4-mm plate-screw construct with a 3.5-mm lag screw and one-third tubular neutralization plate. During torsional testing, torque and displacement were recorded, and stiffness and peak torque were determined. Results. Differences in mean stiffness and mean load at failure were not statistically significant with lag screw–only fixation. The 3.5-mm plate-screw construct outperformed the 2.4-mm plate-screw construct, but neither mean stiffness nor mean load at failure were statistically significantly different. Dynamic testing also demonstrated similar results. Conclusion. Our data suggest that isolated 2.4-mm screws function similarly to one 3.5-mm screw. Although the 3.5-mm plate-screw construct was stiffer, mean load at failure was equivalent for the 2 constructs. These data provide biomechanical evidence to support further investigation in the use of mini-fragment hardware for distal fibula fracture fixation.

Levels of Evidence: Therapeutic, Level V