Finite Element Analysis And Clinical Application Of Humeral Diaphyseal Prosthesis Combined With Auxiliary Plate In The Treatment Of Bone Defect

Objective: 1.To establish a three-dimensional finite element model of normal humerus based on CT scan data and verify the validity of the model;2.To establish the finite element model of humeral diaphyseal prosthesis combined with auxiliary plate for reconstruction of humeral bone defect,and explore the length of auxiliary plate that can make the humerus and prosthesis obtain the best biomechanical properties through the finite element analysis method;3.To investigate the clinical efficacy of diaphyseal prosthesis combined with auxiliary plate in the treatment of humeral shaft metastatic bone cancer complicated with pathological fracture.Methods: 1.CT data in DICOM format of humerus of healthy adults were used to establish a 3D finite element model through 3D simulation modeling software and FEA software.The finite element model of the humerus was simulated by loading different tensile and torsional loads,and the stress distribution of the humerus model was obtained.The validity of the finite element model of the humerus was verified by comparing and analyzing with the biomechanical test of cadaveric bone.2.The 3D models of the diaphyseal prosthesis and the auxiliary plate of different lengths were constructed.Simulate the humerus shaft 5cm bone defects,the auxiliary plate of different length separately assembly to model,establish the geometry model of humeral diaphyseal prosthetic combined with auxiliary plate,finite element analysis of static analysis module was used.Recording and comparing biomechanical data of stress and displacement of humerus,prosthesis and auxiliary plate under different lengths of auxiliary plate.3.Two cases of humeral metastatic bone cancer with pathologic fracture were reported.Reconstruction of bone defects was performed by diaphyseal prosthetic combined with auxiliary plate after resection of tumor segment.Postoperative followup of patients with clinical and radiological regularly.Therapeutic efficacy was evaluated according to the MSTS functional score and ASES scoring system.Results: 1.Under the axial tensile loads of 20 N,40N,60 N,80N,100 N,120N,140 N,160N,180 N,200N,the humerus finite element model was subjected to the same tensile loads as the cadaver bone biomechanical test,the errors of the results of the FEA and the cadaver bone test were all less than 10%;The humerus finite element model was subjected to the same torsional load as the cadaver bone biomechanical test,and the errors of the FEA and the cadaver bone test were all less than 10% under the torsional loads of 0.5N·m,1.0N·m,1.5N·m,2.0N·m,2.5N·m,3.0N·m,3.5N·m,4.0N·m,4.5N·m,5.0N·m,respectively.The error of the stress peak of the intact humerus under different loads was less than 10% compared with the cadaver bone test,and the location was all in the middle and lower 1/3 of the humerus.2.When 200 mm auxiliary plate is used under tensile load,the displacement values of entirety and diaphyseal prosthesis are the minimum.Increasing the length of auxiliary plate can share more stress on the entirety and diaphyseal prosthesis.When the auxiliary plate with the length of 200 mm is used under torsional load,the displacement of the entirety and diaphyseal prosthesis is the minimum,and the torsional resistance of the prosthesis is better.With the 160 mm auxiliary plate,a lower stress distribution was obtained for both diaphyseal prosthesis and the humerus,and more torsional load could be shared by auxiliary plate.3.All the patients were followed up.At the last follow-up,there were no complications such as wound infection,radial nerve injury,prosthesis loosening and local recurrence of tumor.The MSTS scores were 26 and 25,and the ASES scores were 87 and 83,respectively.Conclusions: 1.The 3D finite element model of the humerus of normal human body was successfully established,and the FEA was carried out by simulating different tensile and torsional loads.The validity of humeral finite element model was verified by comparing with the biomechanical test of cadaver bone.2.The use of 200 mm length of auxiliary plate combined with diaphyseal prosthetic in the treatment of humeral shaft bone defects had good tensile and torsional resistance,good initial stability,and reduce the risk of failure and dislocation after implant.However,in clinical surgery,due to the limitation of incision length,the use of 160 mm auxiliary plate combination can also achieve better biomechanical properties of the humerus and prosthesis.3.The clinical effect of diaphyseal prosthesis combined with auxiliary plate in the treatment of humeral shaft metastatic cancer complicated with pathological fracture is satisfied,and the early loosening of the prosthesis can be prevented by the addition of auxiliary plate.