Dynamic Condylar Screw (DCS) versus Condylar Blade Plate (CBP) in Complex Supracondylar Femoral Fractures - A Biomechanical Study

摘要

The ideal implant for the distal femur fractures is controversial. The purpose of this study is to compare, the mechanical stiffness of the bone/osteosynthesis material (DCS or CBP) construct in complex supracondylar femur fractures. 12 synthetic femora were fixed in the distal part with 6 DCS and 6 CBP. A bone defect of 1.5 cm simulated a supracondylar complex fracture (type A3/AO). The femurs were sectioned on the mid shaft while the proximal ends of the distal fragments were blocked in a metallic adapter sleeve. These complexes were tested for 7 load types: 1. internal compression; 2. external compression; 3. anterior compression; 4. posterior compression; 5. axial compression; 6. external torsion; 7. internal torsion. Compression tests were performed up to 350 N and the applied torsion attended 25 Nm. Each test was repeated 6 times in order to calculate the statistic dispersion. The measurements for DCS were realized with and without compaction screw. Compression force and loading force were measured by a force transducer and linear deformation values for the compression were measured by two inductive transducers applied in frontal axis (TD1) and sagittal axis (TD2). Data acquisition was realized by a digital data acquisition system DAQ1200 and a laptop. Based on our measurements, by reporting the loading/unloading force to the transducer (TD1 and TD2) displacement we represented hysteresis cycles as diagrams. The obtained preliminary results were statistically processed by calculating the mean stiffness (square mean error) and the "p" value. The femur-DCS complex is more stable in all compression types except the posterior and axial one, where CBP appear to be more resistant for TD2 transducer. The study on synthetic bones suggests that DCS is better than CBP in most loading tests; the DCS compaction screw confers an increased stability to the construct.