Biomechanical comparison of headless antegrade screw versus retrograde cortical screw for coronoid fracture fixation

Objective: Posterior-to-anterior directed screws are stronger than anterior-to-posterior directed screws for coronoid fracture fixation. Anterior approaches that facilitate direct reduction and fixation of coronoid fractures have been described. The present study was based on the hypothesis that anterior-to-posterior headless screw (Acutrak Mini® 3.5 mm × 26 mm, Acumed, Hillsboro, Oregon, USA) fixation of coronoid fractures would be as strong as posterior-to-anterior 2.7 mm Association for Osteosynthesis (AO) cortical screw fixation. Methods: This study included 14 ulnas obtained from 14 formalin-preserved adult cadavers. Coronoid type 2 fractures were created and fixed randomly using anterior-to-posterior headless screws (antegrade group) and posterior-to-anterior 2.7 mm AO cortical screws (retrograde group). The experimental constructs were loaded until 2 mm of displacement. Failure load (N), fixation stiffness (Nmm–1), and indentation stiffness were calculated. Results: Failure load was higher in the retrograde screw group (p=0.03), whereas loading stiffness values of the fixation devices and bones did not differ between the 2 fixation groups (p 0.05). Conclusion: The present study failed to show that anterior-to-posterior directed headless screw fixation of coronoid fractures could adequately replace posterior-to-anterior placed screw fixation.