Biomechanical Study Onreconstruction Of Humeral Defect Bydiaphyseal Prosthesis Combinedwith Auxiliary Plate

Humerus is one of the predilection sites where primary malignant bone tumors and metastasis take place,often with tumor resection as treatment.For limb reconstruction after tumor resection,intercalary allograft,autogenous,implantation and other methods are currently available.With the imaging technology,prosthetic manufacturing techniques and surgical techniques improvement,artificial prosthesis reconstruction has been widely used in the limb salvage.As a new artificial prosthesis,the modular prosthesis has attracted much attention because of its advantages of relatively simple operation,short hospital stays,immediate weight-bearing,low complication,good biomechanical performance and so on.At present,the clinical application of the modular prosthesis in the humeral shaft is rare,and the biomechanical properties of the humerus and prosthesis after implantation are not clear which restricts its clinical application and further optimization design.In this study,we designed a new type modular prosthesis and verified its properties in vitro experiment and three-dimensional finite element analysis.So as to provide a scientific basis for the clinical use and optimization design of the prosthesis.In the present study,we use the 3-D print model to perform preliminary experiments to familiarize with the experimental procedure and summarize the problems encountered in the experiment and propose a solution.Then,we take the fresh humerus subjected to toothpaste entrapment,patch placement and loading tests.In order to simulate the humerus in the biomechanical environment,the experiments were carried out in the humeral mechanical axial tensile loading and around the axis of the torsion loading,displacement and strain date was collected.The experiment was divided into three steps one by one.Fristly,the humerus was subjected to the loading experiment.Secondly,the 5 cm length defect of the middle humerus shaft was artificially established and reconstructed with only prosthesis(without auxiliary fixation system).Finally,Ti plate was added and the loading was performed again.Displacement and strain averaged after loading five times.Although the cadaveric bone experiment can effectively respond to the strain changes at the measured position,the experimental environment and some unpredictable factors will affect the experimental results,and this method can only get the strain of the patch position but can not get the whole or key components such as the surface of the implant stem,the fastening screw.The three-dimensional finite element model of the humerus was established based on the CT scan and the prosthesis model based on software.In accordance with the cadaveric bone experiment,the finite element model was set up and loaded,and boundary conditions were performed with the cadaveric bone experiment.Experimental results show that reconstruction of the new modular prosthesis can be used as an effective limb salvage therapy.The prosthesis has a better initial stability to cope with the complex biomechanical environment of upper limb,and the design of the auxiliary Ti plate reduces the risk of loosening and dislocation of the prosthesis.At the same time,the validity and accuracy of the three-dimensional finite element model of humerus were validated,and the stress distribution of the humerus and prosthesis under tension and torsion loads was obtained,which provided a theory for clinical use and further optimization design of the prosthesis in accordance with.