Biomechanical Studies Of Steel Plate And Cement In Treatment Of Different Porcine Distal Femur Defects

ObjectiveTo investigate the biomechanical effects of different distal femur defects reconstructedwith steel plate and cement by using steel plate and cement to reconstruct the differentporcine distal femur defects, in order to find out the most optimal methods ofreconstruction of the distal femoral defects.Methods50porcine femora were randomly divided into10groups: Group M：Intact femora;Group D1, C1, P1: femora with1/4bone defect; Group D2, C2, P2: femora with2/4bonedefect; Group D3, C3, P3: femora with3/4bone defect. Femora from group D1, D2, D3were reconstructed with cement alone. Femora from group P1, P2, P3were reconstructedwith cement and steel plate.All femora were transected15cm proximal to the joint line by a handheld saw. Eachfemur was set into the INSRON MODEL8032multifunctional testing machine andINSRON MODEL5969multifunctional testing machine for testing. Load and displacementwere recorded during testing and the load vs displacement curve was plotted. The load tofailure (N) and the stiffness (N/mm) was calculated and recorded for each femur. Inaddition, the mode of failure was noted and recorded for each specimen.ResultsAll the femora except one femur from the group D1and two femora from the groupD2and three femora from group D3survived the initial2000cycles. The femora from thegroup D1, group D2and group D3that not survived the initial2000cycles was failed atthe mode of intra-articular. In those femora survived the initial2000cycles, four femorafrom the group C1and three femora from the group C2and three femora from the groupC3were failed at the mode of intra-articular at the failure load. The rest femora were failedat the mode of extra-articular at the failure load. The four femora that failed at the mode of intra-articular due to the cement were pulled out from the defects.The average load to failure for group D1femora was stronger （p=0.033）than theaverage load to failure for group D2femora, The average load to failure for group D2femora was stronger （p=0.015）than the average load to failure for group D3femora.The average load to failure for group C3femora was stronger （p=0.037）than theaverage load to failure for group C2femora, The average load to failure for group C2femora was stronger （p=0.001）than The average load to failure for group C1femora.The average load to failure for group P3femora was stronger （p=0.000）than Theaverage load to failure for group P2femora, The average load to failure for group P2femora stronger （p=0.000）than the average load to failure for group P1femora.The average load to failure for group P1femora similar （p=0.0197）to the averageload to failure for group C1femora, The average load to failure for group P2femora wasstronger（p=0.002）than the average load to failure for group C2femora. The average loadto failure for group P3femora was stronger （p=0.002）than the average load to failure forgroup C3femora.Conclusion1. The biomechanical strength of distal femur was reduced by defects when they cometo1/4bone defect, the greater in the defect the more noticeable decline in mechanics.2. Femora with1/4bone defect needs to be reconstructed with crossed screwsengaging the opposite cortex in order to prevent the cement slipping from the defects.3. Femora with2/4bone defect and above2/4bone defects needs to be reconstructedwith cement and steel plate.