PREBENDING AND PRETENSIONING OF THE SMALL 4.5 MM AO TITANIUM LC-DCP

To assess the behavior of the LC-DCP with prebending and pretensioning we tested: gap angle vs. tensioning force without prebending; Bending moment for different prebending angles; In a model using a fiber tube to simulate the bone for different prebending angles and pretensionin g forces of the LC-DCP the deformation in 4 point bending open was tes ted. Maximum prebending angle was 24 degrees, maximum pretensioning fo rce was 2400 N; in human cadaver tibiae angles of 3 degrees, 9 degrees , 24 degrees and forces of 300 N, 1000 N and 1500 N, were tested to lo ok for the difference in a less idealized model. - Results: 1. A near linear curve for gap angle vs, force with an angle of 0.45 degrees/100 N was found between 100 N and 1500 N; 2. We did not find a near linea r bending moment/bending angle curve up to 8 degrees like in the DCP b ut an exponential curve development as it had to be expected by the lo wer modulus of elasticity of titanium; 3. the maximum mechanical stabi lity was found for a angle of 24 degrees and a force of 1500 N. - The titanium LC-DCP shows a different mechanical reaction to prebending an d pretensioning in the bone implant complex compared to stul DCP. Opti mum prebending and pretensioning for axial compression and mechanical stability in the LC-DCP are by far greater than clinically possible. F rom our mechanical testing a prebending angle of 24 degrees and a pret ensioning force of 1500 N would allow the largest axial compression an d show the most resistance against deformation in bending open. In the clinical setting this would result in difficult reduction and therefo re, we recommend a prebending angle of 9 degrees and a pretensioning f orce of 1000 N.