Mechanical analysis of the bone to plate interface of the LC-DCP and of the PC-FIX on human femora

The scope of this analysis was to evaluate the mechanical-behaviour of newl y developed plates at the junction between plate and bone (friction between plate and bone) for the limited contact dynamic compression plate (LC-DCP) and the point contact fixator (PC-Fix) under simulated physiological load and using the tension band principle on the human femur. The intact human cadaveric femora were plated on the lateral aspect accordi ng to the tension band principle (AO) and subjected to a load which simulat ed careful physiological load in single stance. Five strain gauges were glu ed around the bones, parallel to the bone axis, at five levels, whereby thr ee of them had to be covered by a bone plate and the two others were just o utside the plate location. The cross-sectional geometry had been obtained a t these levels using computed tomography. One side was plated using the con ventional compression plate LC-DCP and the contralateral side using the int ernal fixator PC-Fix. The LC-DCP was affixed using screws tightened at diff erent torque values and the PC-Fix at a standard torque value. Motion (slippage) between the plate and the bone was indicated by a hystere sis of the strain reading during loading and unloading. Slippage was more i mportant for the LC-DCP than for the PC-Fix, particularly at the proximal e nd of the plate and when the screws were insufficiently tightened on the LC -DCP. As expected, better stability was obtained with the PC-Fix.