Finite Element Analysis Of The Mechanism Of Proximal Humeral Four-Part Fracture Combined With Dislocation Of Humerus Head And Comparative Study Of Treatment Methods

Part 1 Finite element analysis of mechanism of proximal humerus four-part fracture combined with dislocation of humerus headObjective:To establish a three-dimensional model of the humerus joint and investigate the injury mechanism of four parts proximal humerus fracture combined with dislocation of humerus head by finite element analysis.Methods:The CT scan images of the left shoulder joint of a healthy adult male volunteer were selected as the source of 3D reconstruction data.The data source consisted of 340 high-resolution,1mm spaced tomography images.The image of the shoulder joint was extracted by MIMICS software and imported into 3-Matic software for model design and grid division.Combined with the rotation direction of the humerus head,three-dimensional models of three functional positions of the shoulder joint were established,namely,internal rotation at 45°,neutral position and external rotation at 45°.The three-dimensional model was assigned with ANSYS software,the boundary was constrained,and three external forces were applied to the proximal humerus from anterolateral 45°,lateral 45° and posterolateral 45° with the force size of 650N.The three-dimensional stress distribution and fracture deformation of each component of glenohumerus joint at each position were observed.To analyze the injury mechanism of four parts proximal humerus fracture combined with dislocation of shoulder joint.Results:The stress of proximal humerus was concentrated in the surgical neck and tubercles,and the stress of scapula was concentrated behind the glenoid cavity.In the neutral position of the shoulder joint,the stress of the scapula was concentrated under the scapular glenoid after external force was applied.The external rotation was 45°,and the stress of the scapula was concentrated in front of the glenoid cavity.Conclusion:A simple and fast finite element model of shoulder joint is established.Through the mechanical analysis of the model,it was found that the stress distribution was concentrated in the area around the surgical neck of the humerus,the greater tubercle and the lesser tubercle,which was easy to cause fracture.When the shoulder joint is in internal rotation,it is easy to damage the rear structure of the scapular glenoid,resulting in the rear support position.When the shoulder joint is in external rotation,it is easy to damage the front structure of the scapular glenoid,resulting in anterior dislocation.Part 2 Comparative study on the treatment of four-part fracture of proximal humerus combined with dislocation of humerus headObjective:The incidence of proximal humerus fracture is increasing year by year.As a special type,the incidence of four-part fracture with dislocation of humerus head is also increasing.This type of fracture has always been a difficult problem for clinicians.The objective of this study is to evaluate the clinical efficacy of PHILOS plate fixation and humeral head replacement(HHR),and to explore surgical options for four-part proximal humeral fractures with dislocation of humeral head.Methods:Twenty-eight patients with Neer Ⅳ partial fracture complicated with shoulder dislocation admitted to the orthopedics Department of the Shandong Provincial Hospital Affiliated to Shandong University from June 2016 to June 2021 were selected and divided into PHILOS group(15 cases)and HHR group(13 cases)according to different surgical methods.The operative time,intraoperative blood loss,hospital stay,fracture healing time,Neer shoulder function score were compared between the two groups.Results:In terms of operation time and intraoperative blood loss,the HHR group was better than the PHILOS group,and the difference was statistically significant(P<0.05).In terms of hospital stay,PHILOS was longer than the HHR group,and there was no significant difference,P>0.05.In terms of fracture healing time,HHR group was longer than PHILOS group,the difference was statistically significant(P<0.05).In terms of Neer shoulder joint function score,HHR group was better than PHILOS group at 1 month and 3 months after fracture,the difference was statistically significant(P<0.05).At 9 months after surgery,there was no significant difference between the two groups(P>0.05).15 months after surgery,PHILOS was better than HHR group,the difference was statistically significant(P<0.05).Conclusion:PHILOS plate internal fixation and humeral head replacement can achieve good results in the treatment of Neer Ⅳ partial fracture combined with shoulder dislocation.In terms of short-term benefits,humeral head replacement arthroplasty is superior to PHILOS plate fixation.PHILOS plate internal fixation is superior to humeral head replacement arthroplasty in long-term benefit.