Three-dimensional Finite Element Analysis Of Fibula Support Combined With Locking Plate In The Poor Medial Column Support Proximal Humeral Fracture

Objective:With the deepening population aging process in China,the incidence of proximal humeral fractures and the number of patients undergoing surgery for proximal humeral fractures are increasing.After decades of updating and iterative development,the proximal humeral locking plate has obvious advantages in the treatment of such fractures and is widely used.For the poor medial column support proximal humeral fracture,the use of locking plate alone is often accompanied by high failure rates,such as varus malformation,screw cutout,and even humeral head necrosis.It has become a urgent problem in clinical treatment.Fibula support combined with locking plate treatment is an effective method for the treatment of the poor medial column support proximal humeral fracture.This study intends to make a retrospective analysis method to evaluate its clinical efficacy.In addition,there is also controversy concerning the optimal position of the fibula implanted in the medullary cavity,few related biomechanical studies have been done.This study intends to use the finite element analysis method to divide the humeral bone marrow cavity into 5 areas,and to explore the biomechanical stability of the fibula combined locking plate at different positions of the medullary cavity,which would be good for optimizing the surgical procedures.Methods:1.Clinical researchFrom October 2017 to May 2019,26 elderly patients with the poor medial column support proximal humeral fracture were treated with locking plate combined with allogenic fibular intramedullary support at Department of Orthopaedics,Guangdong Provincial Hospital of Traditional Chinese Medicine.They were 8 men and 18 women,from 65 to 90 years of age(average,74.8 years).According to the Neer classification,2-part fracture was identified in 3 patients,3-part fracture in 16 and 4-part fracture in 7.Their operation time,amount of intraoperative bleeding,postoperative complications and functional scores at the last follow-up were recorded.The humeral neck angles and humeral head heights were compared between preoperation,postoperation and the last follow-up.2.Experimental studyWith the approval of the ethics committee,CT data of the proximal osteoporosis was obtained,and a 5mm osteotomy under the anatomy of the humerus was performed to establish a fracture model of the proximal medial column of the humerus.Taking the center of the medullary cavity as the origin,the position in the medullary cavity is divided into 5 positions:center,anteromedial,anterolateral,posteromedial,and posterolateral.The fibula is placed in the center of the medullary cavity and named FC group.The fibula is placed in the medullary cavity The anterior medial is named F-AM group,the fibula is placed in the anterolateral medullary cavity,named F-AL group,the fibula is placed in the posterior medial medullary cavity,named F-PM group,and the fibula is placed in the posterior lateral medullary cavity,named F-PL group.Five groups of internally fixed models were analyzed according to the three-dimensional finite element method to assign values,mesh,set boundaries and loads to simulate the biomechanical stability of different internally fixed models under indirect violence..Results:1.Clinical researchTheir operation time aver-aged 89.5 minutes and intraoperative bleeding 79.5 mL.They obtained follow-up from 12 to 26 months(average,18.1 months).All the wounds were healed by the first intention.No such complications occurred as neurovascular lesion,shoulder dislocation or humeral head necrosis.However,screw cut-out was observed in one case.According to the Neer’s scoring system,shoulder function was evaluated at the last follow-up as excellent in 3 cases,as good in 15 and as fair in 3,giving a good to excellent rate of 85.7%.The humeral neck angle after operation was 136.4°±5.8°,significantly larger than the preoperative one(106.0°±7.3°)(P<0.05)but insignificantly different from the value at the last follow-up(135.4°±6.5°)(P>0.05).The postoperative distance between the plate top and the humeral head top was 1.6±0.2 mm,insignificantly different from that at the last follow-up(1.5±0.2 mm)(P>0.05)2.Experimental studyFive groups of internal fixation models were analyzed by finite element method to obtain the stress and stress cloud diagram,displacement and displacement cloud diagram of humerus and internal fixation,and the relative displacement of the fractured end.The F-PM group had the smallest displacement,its humerus stress cloud was not significantly different from the remaining four groups,and its internal fixation stability was the best;followed by the F-C and F-AM groups.The worst phase of biomechanical stability is F-AL group and F-PL group.Conclusion:1.Locking plate combined with allogenic fibular intramedullary support can effectively reconstruct the medial proximal column of the humerus,restore the humeral neck angle,facilitate intraoperative fracture reposition and reduce operation time,leading to good functional recovery of the shoulder and prevention of related complications.2.In this experiment,a three-dimensional finite element analysis of the fibula in the center of the medullary cavity,anteromedial,anterolateral,posterior memory,and posterolateral combined with a locking plate for the treatment of the missing medial column fractures of the proximal humerus was performed.It has good biomechanical stability,and the results are in accordance with the concept of fibular position proposed by Gardner.Secondly,the fibula can be placed in the center of the medullary cavity,and the clinical operation can be selected according to the actual condition of the patient.The fibula should be avoided to place lateral as far as possible.