K-wire pullout strength in hand surgery: Impact of diameter, threading length and drilling speed

Abstract

Introduction: The aim of the present study was to assess the impact, combined and in interaction, of diameter, threading length and drilling speed on K-wire pullout strength in a synthetic model of a hand bone.

Material and methods: The material comprised Sawbones® (20 ×20×50mm), K-wires (diameter 1.2mm, 1.5mm, 1.8mm; threading 0mm, 5mm, 10mm, 15mm), a universal chuck with T handle and a drill (speed 0, 320, 500, 830, 1,290rpm), and tensile testing machine and a digital decision aid. The Sawbones® were drilled, varying diameter, threading and speed. The Statistical Design of Experiments (SDOE) methodology enabled the number of trials to be reduced from 300 to 70. Tensile tests at 1mm/s was imposed on the K-wire up to pullout (pullout strength).

Results: There was no interaction between threading length and diameter effects or between drilling speed and diameter effects, but a strong interaction between drilling speed and threading length effects.

Conclusion: Before using K-wires for internal fixation in wrist or hand fracture, the surgeon has to select their characteristics, optimal holding power being theoretically ensured by large diameter wires with long threading inserted by a high-speed drill.

Level of evidence: I, experimental study.

Keywords: Diameter; Drilling speed; K-wires; Pullout strength; Threading length.