[Pre-bending and and tension adjustment of narrow 4.5 mm AO titanium LC-DCP (limited contact dynamic compression plate)].

Unlabelled: 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 pretensioning forces of the LC-DCP the deformation in 4 point bending open was tested. Maximum prebending angle was 24 degrees, maximum pretensioning force 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 look 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 degree/100 N was found between 100 N and 1500 N; 2. We did not find a near linear bending moment/bending angle curve up to 8 degrees like in the DCP but an exponential curve development as it had to be expected by the lower modulus of elasticity of titanium; 3. the maximum mechanical stability 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 and pretensioning in the bone implant complex compared to stul DCP. Optimum prebending and pretensioning for axial compression and mechanical stability in the LC-DCP are by far greater than clinically possible. From our mechanical testing a prebending angle of 24 degrees and a pretensioning force of 1500 N would allow the largest axial compression and show the most resistance against deformation in bending open. In the clinical setting this would result in difficult reduction and therefore, we recommend a prebending angle of 9 degrees and a pretensioning force of 1000 N.