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.

Mechanical Comparison of Headless Screw Fixation and Locking Plate Fixation for Talar Neck Fractures.

For talar neck fractures, open reduction and internal fixation have been thought to facilitate revascularization and prevent osteonecrosis. Newer screw systems allow for placement of cannulated headless screws, which provide compression by virtue of a variable pitch thread. The present study compared the biomechanical fixation strength of cannulated headless variable-pitch screw fixation and locking plate fixation. A reproducible talar neck fracture was created in 14 fresh cadaver talar necks. Talar head fixation was then performed using 2 cannulated headless variable-pitch 4-mm/5-mm diameter (4/5) screws (Acutrak; Acumed, Hillsboro, OR) and locking plate fixation. Headless variable-pitch screw fixation had lower failure displacement than did locking plate fixation. No statistically significant differences were found in failure stiffness, yield stiffness (p = .655), yield load (p = .142), or ultimate load between the 2 fixation techniques. Cannulated headless variable-pitch screw fixation resulted in better failure displacement than locking plate fixation in a cadaveric talus model and could be considered a viable option for talus fracture fixation. Headless, fully threaded, variable-pitch screw fixation has inherent advantages compared with locking plate fixation, because it might cause less damage to the articular surface and can compress the fracture for improved reduction. Additionally, plate fixation can increase the risk of avascular necrosis owing to the wider incision and dissection of soft tissues.