Failure behaviour of AO 3.5-mm titanium cortical screws in combination with LC-DCP plates

Aim: It was investigated if AO 3.5-mm titanium cortical screws used in comb ination with LC-DCP plates for osteosynthesis are likely to break during su rgery. Method: The moments of torque that lead to breakage of the screw wer e determined experimentally in a hardwood model. The insertion angle was va riable: 90 degrees in centric (n = 30) and excentric (n = 30) positioning, 70 degrees (n = 30) and 50 degrees (n = 30). Minimal moments that led to sc rew breakage were compared to insertion moments that were measured intraope ratively in 7 fracture operations (radial, ulnar, tibial, fibular; 32 screw s). Results: Minimal moments that led to screw breakage were 2.6 Nm (90 deg rees centric), 2.8 Nm (90 degrees eccentric), 2.7 Nm (70 degrees) and 2.4 N m (50 degrees). The maximal intraoperatively measured insertion moment was 2.25 Nm (radius). Conclusions: In this investigation, minimal moments that led to screw breakage in an experimental setting were higher than maximal i nsertion moments that were recorded during surgery. It is concluded that sc rew breakage related to the given implant combination is unlikely if correc t surgical technique is performed.