Experimental Examination of Extra- and Intramedullary Osteosynthesis in Femur Fractures and Their Influence on Implant Development

For operative stabilization of fractures we have the possibility of external fixation, fixation with implants on the bone surface and intramedullary implants. Due to the higher leaver arm length of the femur neck the biomechanical load in the trochanteric and subtrochanteric area is the highest. Therefore the load of the trochanteric area in the one lag stand is 3 times and for the subtrochanteric area 4 times higher than the total body weight. Material and methods. Trochanteric and subtrochanteric fractures: 341 corpse femora were tested to analyse the importance of individual characteristics as age, gender, osteoporosis and CCD angle in deceased age over 60 in an alternating test with 4000 cycles up to 2000N and a final maximal load test. (specimens were tested per group). To determine the possibility of stabilization of different types of fractures analogue osteotomies were performed and load tests were performed in the initial series after angle blade plate of 130 and 95 degrees with U profile and 130 degree double T profile (Teubner plate), 135 and 150 degree DHS, Ender nail, Gamma nail, double plate compound osteosynthesis and Orthofix monalateral external fixator. Results. The result was the development of the Gliding nail (GN, S&N company) It was tested according to the same protocol in comparison to the DHS with lateral buttress plate. The WBC was in all groups 100% higher. In a long time alternating load test of 100.000 cycles of 2000N a pair test right to left femour after GN no instability and after DHS with buttress plate instability after 15.000 cycles occurred (deformation more than 25mm). Supracondylar fractures. The positive effect of a rotation stable fixation in the GN lead us to develop also a retrograde femur nail with as main characteristics offers the possibility of angle stable fixation of the condylar fragment with a blade/screw fixation (RGN). In a alternating load with 1000cycles and 700N maximal load tests with eccentric medial condyle loading the RGN showed a 50% lower cut trough compared to the DFN. Conclusions Complex biomechanical studies demonstrated, with no doubt, that the Gliding nail as well as retrograde gliding nail have unparalleled results regarding the construct stability, with few complications by comparison with other implants that are available for this kind of fractures.