CME OnDemand: 2022 AOFAS Annual Meeting-Preventing Iatrogenic Fibula Fractures using the Push-Pull Technique: A Biomechanical Comparison of Unicortical vs Bicortical Post Screws

Preventing Iatrogenic Fibula Fractures using the Push-Pull Technique: A Biomechanical Comparison of Unicortical vs Bicortical Post Screws

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The study examines the use of unicortical and bicortical post screws during the Push-Pull Technique for fracture reduction in distal fibula fractures. The findings suggest that bicortical screws provide greater strength and stability compared to unicortical screws. Unicortical post screws may be acceptable for fractures that require minimal distraction, but for extensive reductions, a bicortical post screw is recommended to prevent iatrogenic fibula fractures. <br /><br />The study used four pairs of fresh-frozen human cadaveric lower limbs. One leg from each pair received a unicortical post screw and the other received a bicortical post screw. An oblique osteotomy was performed on the distal diaphysis of the fibula to simulate a displaced fracture. A 6-hole tubular locking plate was attached distally with two unicortical locking screws, and either a unicortical or bicortical post screw was placed proximally.<br /><br />The legs were mounted to a wooden jig and secured to an MTS testing system. A lamina bone spreader was used to apply a compressive load to the top ratcheting handle of the spreader. The force applied, displacement, and number of ratchet clicks were recorded.<br /><br />The results showed that all unicortical screws failed at under 15 ratchet clicks, while all bicortical screws failed through bending without visible damage to the bone. Statistical analysis showed significant differences in displacement and energy absorbed between the two types of screws.<br /><br />In conclusion, the study recommends using bicortical post screws for the Push-Pull Technique in distal fibula fractures to prevent iatrogenic fractures. Unicortical screws may be acceptable for fractures that require minimal distraction. The findings contribute to the existing literature on fracture reduction techniques and provide insights into the biomechanical considerations of using different types of post screws.

Asset Subtitle

Sheldon A. McCown, BS, Paul J. Weatherby, Randal P. Morris, BS, Jie Chen, MD, MPH

Keywords

unicortical post screws

bicortical post screws

Push-Pull Technique

fracture reduction

distal fibula fractures

strength and stability

minimal distraction

iatrogenic fibula fractures

biomechanical considerations

fracture reduction techniques