[A biomechanical comparison of Acutrak headless compression screw and AO cannulated lag screw for the fixation of Hoffa fracture].

Objective: To compare the stability, strength of Letenneur type I Hoffa fractures fixed by Acutrak headless compression screws and AO cannulated lag screws.

Methods: 12 models of Letenneur type I Hoffa fractures were randomly divided into 4 groups, which were fixed with two AO cannulated lag screws or Acutrak headless compression screws anteroposteriorly or posteroanteriorly. The stress between two fragments of all specimens was tested. Axial compression test, the cycle load test and the limit load test were successively performed in every specimen.

Results: In axial compression test, displacement of Acutrak headless compression screw groups was lower than that of AO cannulated lag screw anteroposteriorly (P < 0.05). The load to failure for Acutrak headless compression screw groups was higher than that of AO cannulated lag screws (P < 0.05), no matter in anteroposterior or posteroanterior direction.

Conclusion: The strength and stability of Letenneur type I Hoffa fractures fixeded with Acutrak headless compression screw were superior to those provided by AO cannulated lag screw. The direction of screw affects the initial stability for AO cannulated lag screw, other than Acutrak headless compression screw.