| Objective: Using the image data to establish normal elbow joint and triad injure elbow joint models,including humerus,ulna,radius,medial and lateral ligament complex,and articular cartilage.Finite element method(FEM)was used to study the biomechanical effect of the Internal Joint Stabilizer of the Elbow(IJS-E)in the injury of the coronoid process and anterior bundle of the MCL(a-MCL)of the elbow joint,to explore its stabilization effect on the brachiolumnar joint,and to provide biomechanical evidence for clinical application.Methods: Through CT and MRI scanning of right elbow extension position in a healthy adult male volunteer,the obtained image data were imported into Mimics 21.0 software in Dicom format.After extracting and processing the data,the normal elbow joint model was constructed.The model was repaired,noise reduction,assembly,meshing and other processing using Geomagic Studio 2014,Pro/E5.0,Hypermesh 14.0 and other software,and finally the normal elbow joint model A was obtained.After the effectiveness of the model was verified,the coronal process and a-MCL of model A were destroyed to obtain model A1,in which the coronal process of group A1 model needed to be cut by 1/4,2/4,3/4,and 4/4,respectively.Model A2 was obtained by installing IJS-E to each model of A1,and model A3 was obtained by installing IJS-E to model A.In the finite element pre-processing MSC.Patran2019 software and finite element post-processing MSC.Nastran2019 software,the parameter setting,load application,material assignment and subsequent operating conditions of each model are analyzed.The external load of the same size and direction is applied to the above model.The pressure on the brachial-ulnar articular surface,forearm valgus angle and relative displacement distance of humerus at different flexion angles of each model are collected to further compare the stability between each model.Results:1.The elbow joint model was successfully established using finite element software and its effectiveness was verified,which can provide a basis for subsequent biomechanical analysis.2.Under the axial load of 100 N at the humerus end,the peak stress of the ulna and radius articular surface was about 0.54MPa～1.23 MPa in the process of elbow flexion from 0° to120° in group A;During the process of elbow 120°,the peak stress on the articular surface of the ulna and radius was about 0.42MPa～0.81 MPa,which was smaller than that of group A under the same elbow flexion angle;the elbow joint of group A1(coronoid osteotomy1/4～4/4)was flexed from the elbow From 0° to 120° elbow flexion,the peak stress of the articular surface of the ulna and radius was about 0.81MPa～1.92 MPa,and at the same elbow angle,the stress was greater than that of group A,especially when the coronoid osteotomy was 3/4 and above;A2(1/4～4/4 of the coronoid osteotomy,with IJS-E installed)in the elbow joint from 0° of elbow flexion to 120° of elbow flexion,the peak stress on the articular surface of the ulna and radius was about 0.59 MPa～1.31 MPa.When compared with the degree of osteotomy,the stress was lower than that of group A1,and was close to that of group A before 4/4 of coronoid osteotomy.3.Under the axial load of 100 N on the humerus,the anterior displacement of the humerus and ulna at the elbow joint in group A was about 1.8mm～4.0mm during the process of elbow flexion from 0° to 120°.In the process of flexing the elbow to 120°,the anterior displacement of the humerus at the ulnar end was about 1.3mm～3.5mm,which was smaller than that of group A under the same elbow angle;The anterior displacement of the humerus and ulnar humerus was about 2.6mm～8.9mm during the process of flexing the elbow from0° to 120°.At the same elbow angle,the displacement was greater than that of group A,and with the increase of ulnar coronoid osteotomy,The forward displacement value of the humerus increased;the forward displacement value of the humerus at the ulnar end of the humerus in the A2 group(coronoid osteotomy 1/4 to 4/4,with IJS-E installed)of the elbow joint from 0° of elbow flexion to 120° of elbow flexion About 1.6mm～6.2mm,when the degree of elbow bending and the degree of osteotomy are the same,the displacement is smaller than that of group A1,and it is closer to that of group A before 4/4 of coronoid osteotomy.4.Under the load of 20 N laterally on the forearm,the forearm valgus angle of the elbow joint in group A was about 5.3°-8.0° during the process of elbow flexion from 0° to 120°.During the process,the forearm valgus angle was about 4.6°～6.5°,which was smaller than that of group A under the same elbow angle;in group A1(coronoid osteotomy 1/4 to 4/4)the elbow joint ranged from 0° elbow flexion to 120° elbow flexion During the process,the forearm valgus angle was about 6.7°～14.6°.At the same elbow angle,it was greater than that of group A,and with the increase of ulna coronoid osteotomy,the valgus angle of the same model increased;A2(coronoid osteotomy 1)/4 to 4/4,with the installation of IJS-E),the forearm valgus angle was about 5.9°～10.2° during the process of elbow flexion from 0°to 120° of elbow flexion in the IJS-E)group.Less than group A1,but greater than the valgus angle of group A.Conclusion:1.In the injury of elbow triad,IJS-E can maintain the stability of brachiulnar joint to a certain extent,avoid posterior dislocation and valgus instability of elbow joint,and provide temporary stability for fracture and ligament healing.2.When the ulnar coronoid process fracture does not exceed 2/4,that is,in Regan-Morrey type II and type I,IJS-E has a strong stabilizing effect and can be applied in surgery to replace the repair of the coronoid process and anterior bundle of the medial collateral ligament.3.When ulnar coronoid process fractures exceed 2/4 and are associated with injury of the anterior bundle of the medial collateral ligament,IJS-E cannot effectively maintain elbow stability,and other surgical approaches need to be considered for repair at this time. |
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