Stability of the distal phalanx fracture — A biomechanical study on the importance of the nail and the influence of fixation by crossing Kirschner wires

Abstract

BackgroundWith respect to the stability of displaced distal-phalanx fracture, the relevance of nail loss and the biomechanical effects of fixation using crossed Kirschner wires have not been investigated. The present study aimed to determine whether the nail or the type of fixation contributes to stabilizing distal-phalanx fracture. MethodsIn 48 specimens (fingers), a model of the comminuted fracture of the distal phalanx (AO type A3) was created by resecting a 1-mm osseous segment from the distal phalanx. Specimens were assigned to one of four groups, depending on whether the fracture was accompanied with nail loss, and whether the fracture fixation employed a single Kirschner wire or a crossing of two Kirschner wires. Each specimen was subjected to either a bending or a torsion test. FindingsRegardless of the fixation form, the mean peak bending and torsion forces were higher for the specimens with the nail intact. Furthermore, these forces were also higher in specimens which had received fixations based on the Kirschner wires, compared to those specimens which had received fixations based on a single Kirschner wire. The highest mean peak torque 1.39 (0.12) N·m was found for the specimens with no nail loss and fixation using two crossed Kirschner wires, while the lowest mean peak torsion 0.46 (0.02) N·m was found for specimens with nail loss and fixation using a single Kirschner wire. InterpretationOur results suggest that the nail can provide additional stability for comminuted fractures of the distal phalanx after fixation. Furthermore, when nail loss occurs, fixation using two crossed Kirschner wires can provide significantly more stability than fixation using single Kirschner wire.